ACS Publications. Most Trusted. Most Cited. Most Read
Self-Standing Lignin-Containing Willow Bark Nanocellulose Films for Oxygen Blocking and UV Shielding
More

OR SEARCH CITATIONS

My Activity
Publications

Figure 1Loading Img
Download Hi-Res ImageDownload to MS-PowerPointCite This:ACS Appl. Nano Mater. 2021, 4, 3, 2921-2929
  • Open Access
Article

Self-Standing Lignin-Containing Willow Bark Nanocellulose Films for Oxygen Blocking and UV Shielding
Click to copy article linkArticle link copied!

Open PDFSupporting Information (1)

ACS Applied Nano Materials

Cite this: ACS Appl. Nano Mater. 2021, 4, 3, 2921–2929
Click to copy citationCitation copied!
https://doi.org/10.1021/acsanm.1c00071
Published February 26, 2021

Copyright © 2021 American Chemical Society. This publication is licensed under

CC-BY 4.0 .

Abstract

Click to copy section linkSection link copied!
High Resolution Image
Download MS PowerPoint Slide

Developing the bio-based barrier material to substitute the petroleum-based one is the trend in functional packaging applications. Utilization of the abundantly underappreciated bark biomass is attractive from the sustainability point of view; however, an upgraded approach is required to maximize the performances of the lignin-containing cellulose nanofibril (LCNF) films from willow bark. Herein, hot water extraction (HWE) and microfluidization were studied for their effect on the yield of LCNF and its film performance after treatment of aqueous p-toluenesulfonic acid. The resultant HWE films were superior to the nontreated ones regarding yield, moisture, and oxygen barrier properties. In particular, the HWE films achieved an oxygen permeability of 3 cm3·μm/m2·kPa·day at 50% relative humidity, which is among the lowest achieved for single bio-based materials and comparable to commercially available synthetic barrier films. The LCNF films attained complete blocking of UV light transmission within the wavelength range of 290–400 nm. Overall, this study shows that HWE pretreatment not only allows the recovery of high-value extracts, but also significantly improves the yield of LCNF and its barrier performances. The biocompatible, lignin-containing, and self-standing hydrophobic nanocellulose films show promise as a barrier layer against UV radiation and oxygen permeation in food packaging and other applications.

This publication is licensed under

CC-BY 4.0 .
  • cc licence
  • by licence
Copyright © 2021 American Chemical Society

Subjects

what are subjects

Keywords

what are keywords

Introduction

Click to copy section linkSection link copied!
Approximately one-third (roughly 1.3 billion tons) of all edible food produced for human consumption is wasted annually in the world, (1) which equals to a significant squandering of natural and human resources from a global perspective in planting, harvesting, and transporting. Although there is no established correlation between shelf life and food spoilage, food packaging has gained considerable attention in preventing food waste by maintaining quality to prolong the shelf life of food and beverages. (2) Although plastic packaging has gradually replaced the traditional glass and metal packaging because of its advantages regarding weight, cost, and flexibility in design, plastics often suffer from poor barrier protection against oxygen and light. (2)
For instance, the cost-efficient artificial fluorescent lighting system that is favored by the retailers has high quantum energy due to its bands between 315 and 365 nm, which can extract protons from protein- or fat-based food. The photosensitizer-induced photo-oxidation can be easily activated especially in the presence of oxygen (3) and may cause irreversible loss of nutritional values and taste (4) and possibly enhance the formation of undesirable odors and flavors. (5) As known, photon energy is inversely proportional to the wavelength of the light source according to the Planck–Einstein relation. Therefore, the ultraviolet (UV) band (100–400 nm) carries a higher energy than visible light (400–700 nm) and can activate a higher rate of photo-oxidation. (6) In other words, the rate of photo-oxidation depends primarily on the presence of both oxygen and UV light. On the other hand, there has been an emerging trend to shift from petroleum-based polymeric matrices towards more environmentally friendly cellulose-based materials. (7)
In this regard, development of UV-shielding films or filters for food packaging is significantly required to block the transmission of the energetic UV radiation, i.e., the regions of UVB (290–320 nm) and UVA (320–400 nm). Incorporating UV light absorbers like inorganic metal oxides (e.g., nanosized titanium dioxide and zinc oxide), (8) organic compounds (e.g., salicylates and cyanoacrylates), hybrid compounds (e.g., hydroxyl benzophenone blended with silicon alkoxides), (4) and natural light absorbers (e.g., betel extract) (9) into the polymeric material can increase its absorption efficacy against natural or artificial UV light. Although the deterioration of the food can be significantly reduced, there remains the risk that UV absorbers can migrate into the food and may cause carcinogenic effects on human health. (10,11) The polymer photostabilization can also be strengthened by introducing stabilizers, such as excited-state quenchers, peroxide decomposers, and free radical scavengers. (12)
Minimizing or blocking oxygen permeation through the package is another key factor to prevent the rate of photo-oxidation. Nanocellulose has been known for its features such as high surface area and dense nanofibril network structure, which allow its use as an oxygen barrier layer for food packaging. (7) The major disadvantage is that the nanofibril can interact with the water molecules because of its associated hydroxyl groups, which can cause unwanted physical deformation in an atmosphere of oxygen and water. Reported approaches have been taken to improve the oxygen barrier performance of nanocellulose by tuning its crystallinity or introducing functional hydrophobic groups (like the alkyl type), which includes the oxidation pretreatments (e.g., TEMPO-catalyzed oxidation, (13) regioselective oxidative, (14) and butylamino-functionalization (15)), surfactant adsorption, (16) and polymer grafting. (17)
Therefore, engineering the nanocellulose-based thin film as a barrier layer inside the food package can help in preserving the freshness of food and beverages by blocking external oxygen and UV light. The inherent dark color of the willow bark (WB) fibril films, (18) along with other intriguing features, e.g., low moisture sorption behavior, high hydrophobicity, and richness of phenol-type compounds, inspired us to investigate especially the oxygen and UV-blocking performance of such nanocellulose films. Hence, an in-depth analysis of water vapor, oxygen barrier, and the UV-blocking performance of willow bark fibril films was executed. In addition, the effects of hot water extraction (HWE) and microfluidization were investigated here for achieving a complete valorization of the willow bark.

Experimental Section

Click to copy section linkSection link copied!

Materials and Chemicals

All chemicals and solvents were used as supplied from Sigma-Aldrich unless described elsewhere. The four-year-old willow hybrid “Karin” (SalixEnergi Europa AB) was harvested from the plantation site of the VTT Technical Research Center of Finland located in Kyyjärvi on May 13, 2015 and immediately transferred to a −20 °C freezer to keep it fresh. The bark was stripped off manually and cut into 2 cm pieces before keeping it at room temperature until further use. The microfibrillated cellulose (MFC) was prepared from bleached Kraft pulp (mixture of pine and spruce) using the Masuko supermass colloider (MKZA10-15J, Japan) and was used as a reference sample.

Experimental Flow

Hot water extraction (HWE) of the bark was performed at 80 °C for 30 min (Figure 1). Both the HWE-treated and nontreated bark were processed in a disk refiner to obtain coarse fiber bundles (FBs) before introducing them into aqueous 60 wt % p-toluenesulfonic acid (p-TsOH) at a p-TsOH/FB ratio of 10:1 at 80 °C for a period of 20 min to liberate the fibrous cellulosic solid residue (FCSR). The mechanisms involved catalysis of the dissolution or hydrolysis of carbohydrate and lignin through the ionized tosylate group (pKa for p-TsOH = −2.8 at 20 °C). Furthermore, p-TsOH could be simply extracted after the re-cycling of the hydrolysate due to its low water solubility. (19)

Figure 1

Figure 1. Experimental flow of fabricating lignin-containing cellulose nanofibrils (LCNF) and LCNF films from hot water-extracted willow bark (HWEWB), using a recyclable acid hydrotrope (p-TsOH).

High Resolution Image
Download MS PowerPoint Slide
The dissolved high-molecular-weight (HMW) substances were precipitated by diluting the acid liquor with cold water below the lower concentration level required for the hydrotrope, followed by centrifugation and lyophilization for further analyses. FCSR was mechanically grinded by the supermass collider to avoid clogging of the microfluidizer (Microfluidic M-110P equipped with 1.5 kW output) used for further fibrillation. Then, well-grinded FCSR fractions were continuously passed through the z-shaped chamber of the microfluidizer with the nozzle adjusted from 400 to 100 μm. The effect of defibrillation was controlled by adjusting the cycle numbers from 6 (20) to 12. The lignin-containing cellulose nanofibrils (LCNF) were further fabricated into self-standing thin films using the combined slow filtration and hot pressing methods described earlier. (18) The Sefar Nitex polyamine monofilament (pore size: 10 μm) was used here to screen the 1% LCNF suspensions under the pressure of 2.5 bar. The LCNF film was then dried under room temperature for 4 min and then pressed for a further 2 h under a pressure of 1.8 kPa at 100 °C. Descriptive statistics was adopted in this study as the statistical method.

Characterization

Chemical Analyses

In order to eliminate their possible effects on lignin quantification, extractives, proteins, and tannins were removed from the samples (willow bark, LCNF) prior to the Klason lignin analysis (Figure S1, Supporting Information). The samples were first extracted with dichloromethane. The extracted samples were then mixed with 1% pepsin solution in 0.1 M HCl at a liquid/solid ratio of 25:1 and incubated by agitation at 37 °C for 16 h to eliminate proteins. The enzyme-treated samples were washed with hot water until neutrality was achieved. The protein content was defined as the weight loss in the pepsin treatment. Tannins were removed by further treatment with 0.1 M NaOH under nitrogen flow at 100 °C for 1 h. (21) The extracted protein- and tannin-free samples were analyzed for lignin and carbohydrates using NREL/TP-510-42618. The carbohydrate analysis was conducted using the high-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection (PAD) (Dionex ICS-3000, CarboPac PA 20 column, Sunnyvale, CA).

Morphology and Tensile Test

Zeiss Sigma VP was used to record the scanning electron microscopy (SEM) images on the morphological structures of LCNF and LCNF films. Sputter coating with platinum/palladium was used to increase the electric conductivity and avoid charging. SEM images were taken at 2 and 5 kV operating voltage for LCNF and LCNF films, respectively. The specimens were preconditioned at 23 °C and 50% relative humidity (RH). The tensile analysis was performed using an MTS 400/M Vertical Tensile Tester equipped with a 2 kN load cell according to ISO 527-1. (18)

Atomic Force Microscopy (AFM) and Contact Angle

Surface roughness and fibril thickness were measured using the AFM imaging technique on a Nanoscope V MultiMode scanning probe microscope (Bruker Corporation, Massachusetts). The radius of curvature from the tip was approximately less than 10 nm. The surface roughness parameters Rq and Ra were calculated on the basis of two or three image replicates. (22) Moreover, thickness distribution of the fibril was determined based on the AFM height measurement. The contact angles were characterized for the films under the CAM 200 (KSV Instruments Ltd., Helsinki, Finland). The detailed parameters were described previously. (18)

Water Vapor Transmission Rate (WVTR)

The WVTR test was performed according to the ASTM E 96/E 96M–05 dessicant method with a minor modification. A preconditioning of samples was performed at 50% relative humidity (RH) as recommended by the standard. Results were calculated from three replicates. The dessicant-filled containers were covered with the sample and sealed mechanically from the edges. The containers were weighed and placed in the humidity-controlled chambers and weighed periodically. The RH gradient and temperature used in these measurements were 0/75% and 23 °C, respectively. The Rotronic RH meter (Bassersdorf, Switzerland) was adopted here for a systematic control of the cabinet temperature and RH prior to each weighing. The thickness of the specimen was determined using a micrometer (Lorentzen & Wettre, Kista, Sweden, precision 1 μm) by taking the average of five measurements. The WVTR and water vapor permeability (WVP) were calculated using the equations below
where ΔW is the weight gain, t is the time, A is the exposed surface area of the sample, l is the sample thickness, Psat is the saturated vapor pressure of water at 23 °C, and ΔRH is the relative humidity gradient over the sample (75%).

Oxygen Transmission Rate (OTR)

OTR was tested using a Systech Illinois 8001 Oxygen Permeation analyzer (IL) according to ASTM D 3985-05. A mask (A Systech Illinois 8001 accessory) was used to decrease the sample surface area to 5 cm2 due to sample size limitation. The pressure gradient was maintained at 1 atm, temperature was set to 23 °C, and the relative humidity of both gases (N2 and O2) was 50%. Two replicates of each sample were measured. Oxygen permeation (OP) was calculated from the OTR result using the equation below.
where l is the thickness of the sample and ΔP is the pressure gradient.

UV Transmittance

The UV transmittance of the LCNF films was measured with at least six technical replicates by a Shimadzu UV 2600 spectrophotometer with ISR-2600 Plus integrating sphere attachment in the wavelength range between 290 and 400 nm.

NMR Spectroscopy

Solid-state 13C cross polarized magic angle spinning (CP/MAS) NMR spectra were measured using Bruker Avance III spectrometer operating at 500 MHz for protons using a double-resonance CP/MAS probehead. Samples were packed into 4 mm OD ZrO2 rotors and plugged with KEL-F endcaps and spun at a spinning frequency of 8 kHz. The length of the contact time for cross-polarization was 1 ms, and a variable-amplitude cross-polarization ramped from 70 to 100% amplitude during the contact time. During the acquisition period, the protons were decoupled using SPINAL-64 decoupling and the length of the acquisition was 27 ms. At least 3000 scans were collected with a 5 s relaxation delay and the spectra were externally referenced to adamantane. 1H NMR, 13C NMR, and phase-sensitive two-dimensional (2D) 1H–13C heteronuclear single quantum coherence (HSQC) spectra were acquired using dimethyl sulfoxide (DMSO)/pyridine (4:1) as the solvent (23) at 22 °C and a 400 MHz Bruker Avance III spectrometer. 1,3,5-Trioxane (δC 93.1, δH 5.12 ppm) and DMSO (δC 39.5, δH 2.49 ppm) were used as internal standards for chemical shift calibration. NMR data was interpreted using TopSpin 3.0 software and image contours were colorized in an Adobe Illustrator. The detailed experimental parameters were similar to those in the previous work. (24) The contents of hydroxyl and carboxylic acid groups were analyzed by quantitative 31P NMR spectroscopy. (25) The HMW was dried in a vacuum oven overnight at 40 °C prior to phosphitylation using 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane (TMDP) and measured as described previously (26) except that the relaxation delay d1 of 5 s was set here. The reported values are the mean values of two independent experiments.
High performance size-exclusion chromatography (HP-SEC): The HP-SEC system employed a series of three PSS MCX 5 μm 300 mm × 8 mm 100, 500, and 1000 Å columns eluted with aqueous 0.1 M NaOH at 30 °C. A variable-wavelength detector set at 280 nm was used to monitor the effluent. Mn and Mw were calculated from a linear calibration curve constructed with narrow-polydispersity polystyrene sulfonate (sodium salt) standards. The samples were first stirred for a few hours at 23 °C and then filtered through a 0.45 μm membrane prior to analysis on the same day.

Results and Discussion

Click to copy section linkSection link copied!

Chemical Composition of LCNF

Figure S2 and Table S1 summarize the chemical compositions of willow bark (WB), hot water-extracted willow bark (HWEWB), and lignin-containing nanofibrils (LCNF) obtained from these after p-TsOH treatment. The yield loss in the pepsin treatment of WB and HWEWB was >10%, indicating that the protein content of the original bark was high (Table 1). In contrast, the pepsin treatment of LCNFs resulted in small yield losses, which showed that the p-TsOH treatment solubilized the proteins. (27) The Klason lignin content of WB (17.3 ± 0.7%), determined after the pepsin treatment, was lower than the previously reported value (24.7 ± 0.1%) (28) due to the pepsin treatment, which indicates that the acid-insoluble lignin content of the bark has been frequently overestimated due to interfering proteins. (29) The mass balance of Klason lignin (Table 1) revealed that hardly any lignin was solubilized in the p-TsOH treatment, which may explain its reported high thermal stability of the willow bark-derived LCNF from similar treatment. (18)
Table 1. Yields of Klason Lignin and Proteins (% of the Original Mass) from the Willow Bark (WB) and Hot Water-Extracted Willow Bark (HWEWB) Together with the LCNF Obtained from Thema
 WBHWEWBWB 6WB 12HWEWB 6HWEWB 12
microfluidizer cycles  612612
yield (%)10010055.155.167.167.1
yield on original bark (%)1007855.155.152.352.3
Klason lignin (%)17.320.832.429.434.530.7
Klason lignin on original bark (%)17.316.417.616.018.316.2
proteins (%)12.613.60.22.70.80
proteins on original bark (%)12.611.00.11.50.40
a

Reported data are mean values of two independent experiments. HWEWB refers to the hot water-extracted willow bark; WB 6 and WB 12 refer to LCNF prepared from the solid residues of willow bark with 6 and 12 rounds of microfluidization; HWEWB 6 and HWEWB 12 refer to LCNF prepared from the solid residues of the hot water-extracted willow bark with 6 and 12 rounds of microfluidization.

Although the LCNF yield was 12% higher from HWEWB than from WB, the overall yields, considering the yield loss in hot water extraction of WB, were comparable. Interestingly, the captured willow bark (Karin hybrid) water extracts (30) are shown to be effective against some specific treaths. Picein, the major bioactive component in the Karin bark water extracts, (30) has a significant role in suppressing the menadione (vitamin K precursor) induced oxidative stress effects on the mitochondrial integrity in neuroblastoma cells. (31) Triandrin acts as a stress-response modifier in regulating plant adaptogenic activity. (32) Furthermore, picein and triandrin can be chromatographically recovered (33) for possible pharmaceutical use.
The main differences between the 13C CP/MAS NMR spectra of the two types of LCNFs were in their signal intensities. The prior hot water extraction increased the pectin yield as indicated by the higher signal intensities at ca. 173, 102 (shoulder), and 70 ppm, all characteristic of polygalacturonic acid (Figures 2, S3, and S4). Obviously, some structural modification of the pectins during the hot water treatment stabilized them against the p-TsOH treatment. A partial demethylation reaction could be the reason for the stabilization because the ratio of the methoxyl (54 ppm) and carboxyl (173 ppm) signals of LCNF was significantly lower when WB was extracted with hot water after the p-TsOH treatment (Figures S3 and S4). On the other hand, the same ratio was larger in the dissolved HMW fraction, which may show a correlation between the degree of methylation and solubilization of pectins in this case. In line with the aforementioned observations, the hot water pretreatment decreased the pectin content (34) and the amount of HMW fraction of the dissolved material from the p-TsOH treatment (Table S2 and Figure S5). On the other hand, the disappearance of arabinose, rhamnose, and galactose signals clearly showed removal of the neutral components of pectin (Figure S2).

Figure 2

Figure 2. Solid-state 13C CP/MAS spectra of (a) the willow bark; (b) LCNF from WB; and (c) dissolved HMW fraction after treating WB with aqueous 60% p-TsOH. Abbreviations: see caption to Table 1. Label numbers: see caption to Table S3.

High Resolution Image
Download MS PowerPoint Slide
The 13C CP/MAS NMR spectra of WB, HWEWB, LCNFs, and the HMW fractions all had similar aromatic/unsaturated bands at 116, 131, 145, and 155 ppm although the signal intensities were lower in LCNF compared with WB (Figures 2 and S3–S5). The HMW fractions had an additional signal at ca. 109 ppm that was earlier assigned to a condensation product of WB’s aromatic substances and hydroxymethylfurfural (HMF) formed from fructose under harsh acidic conditions (Figures 2 and S5). (30,35) Furthermore, strong and sharp aliphatic carbon resonances (30 and 33 ppm) were present in WB and LCNFs made from it and HWEWB (Figures 2, S3–S5, and Table S3). One of these bands (30 ppm) was present also in the spectra of the dissolved HMW fractions, which shows that the aliphatic substances, most probably suberin, (36) were partially solubilized by the p-TsOH treatment. The hot water pretreatment seemed to lead to a lower aliphatic carbon content in LCNFs and a higher content in HMW (Table S4). Additional information on the HMW fractions is reported under Supporting Information (Tables S5–S7 and Figures S6–S8).

Fibril Morphology

SEM imaging was used to visualize the morphological structure of freeze-dried LCNFs (Figures 3 and S9–S12). In addition to thin fibrils, the precipitates or particles of variable size that we observed in the fibril network seem to be larger in WB LCNF than in HWEWB LCNF although the differences are negligible. The mean fibril thickness, measured by AFM image analysis of the LCNF films, was 26 nm (Figure S13). A similar value was reported earlier (18) for fibrils obtained after 30 min milling of p-TsOH-treated willow bark with a super mass colloider.

Figure 3

Figure 3. SEM images of freeze-dried LCNFs prepared from p-TsOH-treated willow bark (WB) and hot water-extracted willow bark (HWEWB) under 6 and 12 cycles of microfluidization: (a) WB 6; (b) WB 12; (c) HWEWB 6; and (d) HWEWB 12.

High Resolution Image
Download MS PowerPoint Slide

Film Barrier Properties

The hydrophobicity of the LCNF films was evaluated based on the water contact angle (WCA) and surface roughness. Willow bark LCNF films had hydrophobic surfaces with WCA values in the range of 107–116° (Table 2 and Figure S14). Furthermore, the surface roughness also contributed to the hydrophobicity of the films (Figure S15 and Table 2). Interestingly, WB 12 stood out possibly as the most hydrophobic among the studied films for featuring highest WCA and lowest surface roughness parameters from both Rq and Ra. In general, the LCNF films made of WB were more hydrophobic than the films made of HWEWB. One possible explanation for this can be derived from the 13C CP/MAS spectra of the LCNF films (Figures S3 and S4) that showed significant resonance bands at 30 and 33 ppm, which were tentatively assigned for the aliphatic suberin hydrocarbons. Hence, the hypothesis is that suberin contributes more to the hydrophobicity than residual lignin does as WB 12 has the highest aliphatic hydrocarbon content among all LCNF films (Table S4). Moreover, WB 12 exhibited the highest tensile index and breaking strain among them (Table S8). The hydrophobicity and presence of lignin (37) seem to have some effect on the mechanical properties of the LCNF films; a similar observation was also reported earlier. (18) The appearance of the fluffy flakes and rectangular-shaped structures that can be seen in Figures 4 and S16–S20 possibly originates from the outer bark of the willow and the polyamine monofilament mesh, respectively. In comparison, the MFC film of softwood kraft pulp had a more homogeneous surface structure, while the LCNF made of willow wood through a p-TsOH treatment reproduced the mesh structure of the support. (18)

Figure 4

Figure 4. SEM images of the LCNF films of p-TsOH-treated willow bark (WB) and hot water-extracted willow bark (HWEWB) after 6 and 12 cycles of microfluidization in comparison with the MFC film of softwood kraft pulp and willow wood LCNF film: (18) (a) WB 6; (b) WB 12; (c) MFC (softwood kraft pulp); (d) HWEWB 6; (e) HWEWB 12; and (f) willow wood after fractionation with 60% p-TsOH.

High Resolution Image
Download MS PowerPoint Slide
Table 2. Surface Roughness Parameters (Rq and Ra) and Water Contact Angle of LCNF Filmsa
sampleRq (nm)Ra (nm)nwater contact angle (°)
WB 614.6 ± 2.110.1 ± 2.92110 ± 7
WB 121.0 ± 0.20.73 ± 0.032116 ± 4
HWE WB 627.3 ± 3.721.2 ± 2.23107 ± 2
HWE WB 1213.1 ± 3.910.2 ± 3.33108 ± 3
a

n refers to the number of analyzed images for roughness parameters. Rq is the root mean square and is defined as the standard deviation of the surface height distribution. Ra is the average height parameter, which is defined as the average absolute deviation of the roughness from a mean line.

The low oxygen permeability values of the willow bark LCNF films (Table 3) demonstrate their excellent oxygen barrier performance. In particular, the HWEWB LCNF films achieved an oxygen permeability of 2.6–3.1 cm3·μm/m2·kPa·day under 50% relative humidity, which is among the lowest ones reported for pure bio-based (38) and commercial synthetic materials (39) and is also comparable to that of covalently functionalized nanocellulose and nanocrystal films (Table 4). (14,15,40) The HWEWB LCNF films showed a lower permeability for both oxygen and water vapor than the films prepared from the bark without the hot water extraction pretreatment. Low-molecular-weight compounds, such as extractives (41) and polyphenols, (42,43) have been speculated to contribute to the plasticization and consolidation of polymer and nanocellulose films. Suberin was reported not only to limit the oxygen diffusion process in willow trees as an adaptation to the flooding environment where willow traditionally grow (44) but also to improve the hydrophobicity of the lignocellulosic fiber network. (45) Thus, the permeation of oxygen and water vapor is a complex phenomenon and it is difficult to specify the reasons for the observed behavior. The degree of crystallinity and the crystalline features of these films may explain their barrier performances. These are beyond the scope of this study.
Table 3. Water Vapor Transmission Rate (WVTR), Water Vapor Permeability (WVP), Oxygen Transmission Rate (OTR), and Oxygen Permeability (OP) of the LCNF Films Produced from Willow Bark (WB) and Hot Water Extracted Willow Bark (HWEWB) after Treatment with p-Toluenesulfonic Acid
 water vapor barrieroxygen barrier
 thickness μmWVTR g/m2·dayWVP g·mm/m2kPa·dayThickness μmOTR cm3/m2·dayOP cm3·μm/m2·kPa·day
WB 668 ± 9227 ± 197.1 ± 0.363 ± 420.0 ± 5.712.0 ± 2.8
WB 1277 ± 3170 ± 76.0 ± 0.173 ± 810.5 ± 4.17.4 ± 2.1
HWEWB 683 ± 4125 ± 54.8 ± 0.283 ± 13.8 ± 0.13.1 ± 0.0
HWEWB 1279 ± 4134 ± 64.9 ± 0.474 ± 23.6 ± 0.42.7 ± 0.2
Table 4. Oxygen Permeability (cm3·μm/m2·kPa·day) of HWEWB LCNF Films in Comparison with Literature Values Reported for Other Bio-Based and Synthetic Filmsa
film typesample descriptionoxygen permeability
present workHWE willow bark LCNF films2.6–3.1
cellulose-basedreductive amination with taurine nanocellulose (14)0.44 ± 0.07
tert-butylamino-functionalized cellulose nanocrystal film (15)0.25 ± 0.07
oxidized cellulose nanofibrils in sodium form (40)2.5
oxidized cellulose nanofibrils in protonated form (40)6.9
starch-based (38)amylose7
amylopectin14
protein-based (39)whey protein with glycerol (2.3:1)76.1
whey protein with sorbitol (2.3:1)4.3
synthetic (39)polyvinylidene chloride0.4–5.1
polyester15.6
high-density polyethylene427
a

All the values were measured at 23 °C and 50% relative humidity similar to the present study.

Inspired by the inherent dark color of the willow bark LCNF films, their UV light-blocking ability was characterized using a spectrophotometer equipped with an integrating sphere. These films were not optically transparent at visible wavelengths. All the films filtered 99.99–99.999% of the UV light at 290–400 nm (Figure 5 and Table S9). This protection is much higher than what could be achieved with LCNF films made of unbleached kraft pulps, not to mention MFC films of bleached kraft pulps. The UV light-absorbing structures in WB and HWEWB originate from lignin and other polyphenols (46,47) that undergo different dehydration and condensation reactions under the acidic conditions of the p-TsOH treatment.

Figure 5

Figure 5. UV–vis transmission spectra of LCNF films produced from willow bark (WB) and hot water-extracted willow bark (HWEWB) in comparison with an MFC film of bleached kraft pulp in the wavelength range of 290–400 nm.

High Resolution Image
Download MS PowerPoint Slide

Conclusions

Click to copy section linkSection link copied!
Natural functional and hydrophobic films of lignin-containing nanofibrils (LCNF) were prepared from willow bark (WB) by treatment with aqueous p-toluenesulfonic acid (p-TsOH). The treatment modified the structure of lignin and other polyphenolic substances of WB and solubilized them partly. Almost no Klason lignin was dissolved in the p-TsOH treatment. Additionally, WB LCNFs had a high suberin content and a low surface roughness, which obviously was a major reason for the hydrophobicity. WB LCNF films had an excellent oxygen barrier and UV protection properties. Pre-extraction of WB prior to the p-TsOH treatment made the LCNF films less permeable to oxygen gas and water vapor. These or similar nanocellulose films could potentially be utilized in sandwich barrier layers, mitigating the photo-induced oxidation in food packaging. The LCNF film preparation could be integrated with recovery of valuable water extracts of WB for its full utilization.

Supporting Information

Click to copy section linkSection link copied!

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsanm.1c00071.

  • Analytical process scheme for preparing samples for chemical composition analysis from willow bark and HWEWB together with their fibril samples; overall chemical composition and carbohydrate composition of the experimental samples; solid-state 13C CP/MAS spectrum of the LCNF fibrils and its associated HMW; HSQC NMR spectra of the dissolved and precipitated HMW fraction in comparison with the enzymatically isolated Karin bark lignin; SEM images of the associated LCNF films; the water contact angle images show the shape of water droplets on the LCNF fibril networks and films; quantitative AFM measurements illustrating the height image of the studied fibrils; ultraviolet (UV) transmittance of the produced LCNF films (PDF)

Terms & Conditions

Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.

Author Information

Click to copy section linkSection link copied!
  • Corresponding Author
  • Authors
    • Tapani Vuorinen - Department of Bioproducts and Biosystems, Aalto University, Espoo FI-02150, Finland;  Orcidhttp://orcid.org/0000-0002-5865-1776
    • Hanna Koivula - Department of Food and Nutrition, University of Helsinki, P.O. Box 66, Helsinki FI-00014, Finland
    • Nina Forsman - Department of Bioproducts and Biosystems, Aalto University, Espoo FI-02150, Finland
    • Mika Sipponen - Department of Bioproducts and Biosystems, Aalto University, Espoo FI-02150, Finland;  Present Address: Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16 C, SE-106 91 Stockholm, Sweden;  Orcidhttp://orcid.org/0000-0001-7747-9310
    • Sami Hietala - Department of Chemistry, University of Helsinki, P.O. Box 55, Helsinki FI-00014, Finland;  Orcidhttp://orcid.org/0000-0003-1448-1813
  • Notes
    The authors declare no competing financial interest.

Acknowledgments

Click to copy section linkSection link copied!

This work made use of the Aalto University Nanomicroscopy Center (Aalto-NMC) premises. The authors thank Ting Guan from Aalto University for her skillful assistance in the initial phase of the experimental development. Appreciation is also extended to Rita Hatakka and Tuyen Nguyen for their assistance with the HPAEC analysis and microfluidizer operation. This work was a part of the Academy of Finland’s Flagship Programme under Projects Nos. 318890 and 318891 (Competence Center for Materials Bioeconomy, FinnCERES).

References

Click to copy section linkSection link copied!

This article references 47 other publications.

  1. 1
    Rutten, M. M. What economic theory tells us about the impacts of reducing food losses and/or waste: implications for research, policy and practice. Agric. Food Secur. 2013, 2, 1– 13,  DOI: 10.1186/2048-7010-2-13
    Google Scholar
    There is no corresponding record for this reference.
  2. 2
    Wang, J.; Gardner, D. J.; Stark, N. M.; Bousfield, D. W.; Tajvidi, M.; Cai, Z. Moisture and Oxygen Barrier Properties of Cellulose Nanomaterial-Based Films. ACS Sustainable Chem. Eng. 2018, 6, 49– 70,  DOI: 10.1021/acssuschemeng.7b03523
    Google Scholar
    2
    Moisture and Oxygen Barrier Properties of Cellulose Nanomaterial-Based Films
    Wang, Jinwu; Gardner, Douglas J.; Stark, Nicole M.; Bousfield, Douglas W.; Tajvidi, Mehdi; Cai, Zhiyong
    ACS Sustainable Chemistry & Engineering (2018), 6 (1), 49-70CODEN: ASCECG; ISSN:2168-0485. (American Chemical Society)
    A review. Applications of cellulose nanomaterials (CNMs) have attracted increasing attention in recent years. One conceivable path lies in their com. applications for packaging, in which their barrier properties will play an important role in detg. their competiveness with conventional materials. This review critically analyzes the performance of CNMs acting as a barrier against moisture and oxygen permeation in CNM films, CNM coated polymers and papers, and CNM reinforced polymer composites, gives some insights into remaining challenges, and brings an overall perspective of compositing CNMs with other materials to achieve balanced properties adequate for barrier packaging. In general, CNMs are a poor moisture barrier but excellent oxygen barrier in the dry state and are still good below 65% relative humidity. The addn. of CNMs can improve oxygen barrier of the resulting polymer composites; however, Neat CNM coatings and films can afford better oxygen barrier properties than dispersed CNMs in coatings and nanocomposites. The morphol. and surface functionality of CNMs can be tailored to maximize the barrier performance of materials comprising them. The higher the surface charge d. of CNMs, the better the barrier performance of coated polymers. Like other oxygen barriers such as ethylene vinyl alc. and cellophane, the moisture sensitivity and sealability of CNMs can be improved by sandwiching them with high moisture resistant and sealable polymers such as a polyolefin. A multilayered structure with layers of CNMs providing oxygen resistance covered by other layers of polymers providing moisture resistance and sealability might be competitive in barrier packaging markets dominated by synthetic plastics.
  3. 3
    Choe, E.; Min, D. B. Chemistry and Reactions of Reactive Oxygen Species in Foods. Crit. Rev. Food Sci. Nutr. 2006, 46, 1– 22,  DOI: 10.1080/10408390500455474
    Google Scholar
    3
    Chemistry and reactions of reactive oxygen species in foods
    Choe, Eunok; Min, David B.
    Critical Reviews in Food Science and Nutrition (2006), 46 (1), 1-22CODEN: CRFND6; ISSN:1040-8398. (Taylor & Francis, Inc.)
    A review. Reactive oxygen species (ROS) are formed enzymically, chem., photochem., and by irradn. of food. They are also formed by the decompn. and the inter-reactions of ROS. Hydroxy radical is the most reactive ROS, followed by singlet oxygen. Reactions of ROS with food components produce undesirable volatile compds. and carcinogens, destroy essential nutrients, and change the functionalities of proteins, lipids, and carbohydrates. Lipid oxidn. by ROS produces low mol. volatile aldehydes, alcs., and hydrocarbons. ROS causes crosslink or cleavage of proteins and produces low mol. carbonyls from carbohydrates. Vitamins are easily oxidized by ROS, esp. singlet oxygen. The singlet oxygen reaction rate was the highest in ss-carotene, followed by tocopherol, riboflavin, vitamin D, and ascorbic acid.
  4. 4
    Kwon, S.; Orsuwan, A.; Bumbudsanpharoke, N.; Yoon, C.; Choi, J.; Ko, S. A Short Review of Light Barrier Materials for Food and Beverage Packaging. Korean J. Packag. Sci. Technol. 2018, 24, 141– 148,  DOI: 10.20909/kopast.2018.24.3.141
    Google Scholar
    There is no corresponding record for this reference.
  5. 5
    Cardoso, D. R.; Libardi, S. H.; Skibsted, L. H. Riboflavin as a Photosensitizer. Effects on human Health and Food Quality. Food Funct. 2012, 3, 487– 502,  DOI: 10.1039/c2fo10246c
    Google Scholar
    5
    Riboflavin as a photosensitizer. Effects on human health and food quality
    Cardoso, Daniel R.; Libardi, Silvia H.; Skibsted, Leif H.
    Food & Function (2012), 3 (5), 487-502CODEN: FFOUAI; ISSN:2042-6496. (Royal Society of Chemistry)
    A review. Riboflavin, vitamin B2, and flavins (as riboflavin building blocks or degrdn. products) are efficient photosensitizers inducing oxidative damage to light-exposed tissue and food by substrate-dependent mechanisms, for which protection is offered by specific nutrients. Phenolic and N-heterocyclic amino acids and their peptides and proteins deactivate triplet-excited state riboflavin in diffusion controlled processes, efficiently competing with deactivation by oxygen, resulting in direct (so called Type I) protein degrdn. through electron transfer or proton-coupled electron transfer. In light-exposed tissue, such often long lived protein radicals may as primary photoproducts initiate lipid and vitamin oxidn. In contrast, for lipid systems, oxygen deactivation of triplet-excited state riboflavin, resulting in formation of singlet oxygen, is under aerobic conditions faster than direct deactivation by lipids, which otherwise under anaerobic conditions occurs as hydrogen atom transfer from polyunsatd. lipids to triplet riboflavin. Singlet oxygen adds to unsatd. lipids and forms lipid hydroperoxides as primary lipid oxidn. products or oxidizes proteins (Type II mechanism). Carotenoids seem not to deactivate triplet riboflavin, while chromanols like vitamin E and plant polyphenols are efficient in such deactivation yielding protection of proteins and lipids by these phenols. Indirect protection against the triplet reactivity of riboflavin is further important for polyphenols as riboflavin singlet excited state quenchers in effectively preventing riboflavin intersystem crossing to yield the reactive triplet state. Riboflavin photosensitization becomes crit. for degrdn. of proteins, unsatd. lipids, and folate, thiamine, ascorbate and other vitamins during light exposure of food during storage. For skin, eye and other tissue exposed to high intensity light, dietary polyphenols like flavonoids are important in direct protection against photosensitized oxidn., while dietary carotenoids may yield protection through inner-filter effects, through scavenging of radicals resulting from Type I photosensitization, and through quenching of singlet oxygen formed in Type II photosensitization. Both carotenoids and polyphenols accordingly counteract the degenerative effect induced by riboflavin exposed to light, although by different mechanisms.
  6. 6
    Majdi, M.; Milani, B. Y.; Movahedan, A.; Wasielewski, L.; Djalilian, A. R. The Role of Ultraviolet Radiation in the Ocular System of Mammals. Photonics 2014, 1, 347– 368,  DOI: 10.3390/photonics1040347
    Google Scholar
    There is no corresponding record for this reference.
  7. 7
    Ferrer, A.; Pal, L.; Hubbe, M. Nanocellulose in packaging: Advances in barrier layer technologies. Ind. Crops Prod. 2017, 95, 574– 582,  DOI: 10.1016/j.indcrop.2016.11.012
    Google Scholar
    7
    Nanocellulose in packaging: Advances in barrier layer technologies
    Ferrer, Ana; Pal, Lokendra; Hubbe, Martin
    Industrial Crops and Products (2017), 95 (), 574-582CODEN: ICRDEW; ISSN:0926-6690. (Elsevier B.V.)
    The review aims at reporting on recent developments in nanocellulose-based materials and their applications in packaging with special focus on oxygen and water vapor barrier characteristics. Nanocellulose materials, including cellulose nanocrystals (CNC), nanofibrillated cellulose (NFC), and bacterial nanocellulose (BNC), have unique properties with the potential to dramatically impact many com. markets including packaging. In addn. to being derived from a renewable resource that is both biodegradable and non-toxic, nanocellulose exhibits extremely high surface area and crystallinity and has tunable surface chem. These features give nanocellulose materials great potential to sustainably enhance oxygen and water vapor barrier properties when used as coating, fillers in composites and as self-standing thin films.
  8. 8
    Jiang, Y.; Song, Y.; Miao, M.; Cao, S.; Feng, X.; Fang, J.; Shi, L. Transparent nanocellulose hybrid films functionalized with ZnO nanostructures for UV-blocking. J. Mater. Chem. C 2015, 3, 6717– 6724,  DOI: 10.1039/C5TC00812C
    Google Scholar
    8
    Transparent nanocellulose hybrid films functionalized with ZnO nanostructures for UV-blocking
    Jiang, Yaoquan; Song, Yuanyuan; Miao, Miao; Cao, Shaomei; Feng, Xin; Fang, Jianhui; Shi, Liyi
    Journal of Materials Chemistry C: Materials for Optical and Electronic Devices (2015), 3 (26), 6717-6724CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)
    Transparent, nanocellulose-ZnO (NC-ZnO) hybrid films were fabricated via a pressure controlled extrusion process using NC fibrils and sheet-like ZnO (s-ZnO) or belt-like ZnO (b-ZnO) nanostructures. The s-ZnO and b-ZnO conjoined with the NC fibrils to form a heterogeneous, fibrous network structure. The NC-ZnO hybrid films with different amts. of ZnO nanostructures showed a synergic feature of high optical transparency and excellent UV-blocking. The results indicated that NC assembled with s-ZnO hybrid film possessed excellent UV-blocking ability in a wide range from 200 to 375 nm, in contrast to NC-b-ZnO. Moreover, the prominent thermal and photo stability of transparent NC-ZnO hybrid films enhanced extensibility and ease of use for diverse biol. applications, which require tolerance of temp. changes.
  9. 9
    Nouri, L.; Nafchi, A. M. Antibacterial, mechanical, and barrier properties of sago starch film incorporated with betel leaves extract. Int. J. Biol. Macromol. 2014, 66, 254– 259,  DOI: 10.1016/j.ijbiomac.2014.02.044
    Google Scholar
    9
    Antibacterial, mechanical, and barrier properties of sago starch film incorporated with betel leaves extract
    Nouri, Leila; Mohammadi Nafchi, Abdorreza
    International Journal of Biological Macromolecules (2014), 66 (), 254-259CODEN: IJBMDR; ISSN:0141-8130. (Elsevier B.V.)
    The antimicrobial, mech. and barrier properties and light transmission of sago starch film incorporated with different percentage of Betel leaf ext. (5%, 10%, 20%, and 30%) were evaluated. With regard to mech. properties, tensile strength decreased when the percentage of ext. increased. Elongation at break (%) and seal strength (N/m) increased with increasing percentage of ext. from 5% to 20%, while decreased for films contg. 30% ext. due to heterogeneity of films in this percentage. With regard to barrier properties, water vapor and oxygen barrier properties decreased in all samples when percentage of the ext. increased. Antimicrobial activity of all the films increased against both Gram pos. and Gram neg. bacteria as percentage of Betel leaf ext. increased, except for Psuedomonas aeruginosa, which was not susceptible at any percentage of the ext.
  10. 10
    Begley, T. H.; Biles, J. E.; Cunningham, C.; Piringer, O. Migration of a UV stabilizer from polyethylene terephthalate (PET) into food simulants. Food Addit. Contam. 2004, 21, 1007– 1014,  DOI: 10.1080/02652030400010447
    Google Scholar
    10
    Migration of a UV stabilizer from polyethylene terephthalate (PET) into food simulants
    Begley, T. H.; Biles, J. E.; Cunningham, C.; Piringer, O.
    Food Additives & Contaminants (2004), 21 (10), 1007-1014CODEN: FACOEB; ISSN:0265-203X. (Taylor & Francis Ltd.)
    The migration characteristics of the UV stabilizer Tinuvin 234 (2-(2H-benzotriazol-2-yl)-4,6-bis (1-methyl-1-phenylethyl)phenol) into food simulants has been measured from polyethylene terephthalate (PET) using HPLC with UV detection. Ethanol/water, isooctane and a fractionated coconut oil simulant (Miglyol) were used as food simulating solvents. The migration characteristics were measured at temps. in the range of 40-70°. Diffusion coeffs. were detd. to be in the range of 1×10-14 cm2 s-1 to 1×10-18 cm2 s-1. At 40°, the amt. of migration into 95% ethanol after 10 days was 2 μg dm-2. Isooctane is detd. to be a good fatty food simulant that provides similar results for PET to those of fatty foods.
  11. 11
    Skocaj, M.; Filipic, M.; Petkovic, J.; Novak, S. Titanium dioxide in our everyday life; is it safe?. Radiol. Oncol. 2011, 45, 227– 247,  DOI: 10.2478/v10019-011-0037-0
    Google Scholar
    11
    Titanium dioxide in our everyday life; is it safe?
    Skocaj, Matej; Filipic, Metka; Petkovic, Jana; Novak, Sasa
    Radiology and Oncology (2011), 45 (4), 227-247CODEN: RONCEM; ISSN:1318-2099. (Association of Radiology and Oncology)
    A review. Background. Titanium dioxide (TiO2) is considered as an inert and safe material and has been used in many applications for decades. However, with the development of nanotechnologies TiO2 nanoparticles, with numerous novel and useful properties, are increasingly manufd. and used. Therefore increased human and environmental exposure can be expected, which has put TiO2 nanoparticles under toxicol. scrutiny. Mechanistic toxicol. studies show that TiO2 nanoparticles predominantly cause adverse effects via induction of oxidative stress resulting in cell damage, genotoxicity, inflammation, immune response etc. The extent and type of damage strongly depends on phys. and chem. characteristics of TiO2 nanoparticles, which govern their bioavailability and reactivity. Based on the exptl. evidence from animal inhalation studies TiO2 nanoparticles are classified as "possible carcinogenic to humans" by the International Agency for Research on Cancer and as occupational carcinogen by the National Institute for Occupational Safety and Health. The studies on dermal exposure to TiO2 nanoparticles, which is in humans substantial through the use of sunscreens, generally indicate negligible transdermal penetration; however data are needed on long-term exposure and potential adverse effects of photo-oxidn. products. Although TiO2 is permitted as an additive (E171) in food and pharmaceutical products we do not have reliable data on its absorption, distribution, excretion and toxicity on oral exposure. TiO2 may also enter environment, and while it exerts low acute toxicity to aquatic organisms, upon long-term exposure it induces a range of sub-lethal effects. Conclusions. Until relevant toxicol. and human exposure data that would enable reliable risk assessment are obtained, TiO2 nanoparticles should be used with great care.
  12. 12
    Yousif, E.; Haddad, R. Photodegradation and photostabilization of polymers, especially polystyrene: review. SpringerPlus 2013, 2, 398  DOI: 10.1186/2193-1801-2-398
    Google Scholar
    12
    Photodegradation and photostabilization of polymers, especially polystyrene: review
    Yousif Emad; Haddad Raghad
    SpringerPlus (2013), 2 (), 398 ISSN:2193-1801.
    Exposure to ultraviolet (UV) radiation may cause the significant degradation of many materials. UV radiation causes photooxidative degradation which results in breaking of the polymer chains, produces free radical and reduces the molecular weight, causing deterioration of mechanical properties and leading to useless materials, after an unpredictable time. Polystyrene (PS), one of the most important material in the modern plastic industry, has been used all over the world, due to its excellent physical properties and low-cost. When polystyrene is subjected to UV irradiation in the presence of air, it undergoes a rapid yellowing and a gradual embrittlement. The mechanism of PS photolysis in the solid state (film) depends on the mobility of free radicals in the polymer matrix and their bimolecular recombination. Free hydrogen radicals diffuse very easily through the polymer matrix and combine in pairs or abstract hydrogen atoms from polymer molecule. Phenyl radical has limited mobility. They may abstract hydrogen from the near surrounding or combine with a polymer radical or with hydrogen radicals. Almost all synthetic polymers require stabilization against adverse environmental effects. It is necessary to find a means to reduce or prevent damage induced by environmental components such as heat, light or oxygen. The photostabilization of polymers may be achieved in many ways. The following stabilizing systems have been developed, which depend on the action of stabilizer: (1) light screeners, (2) UV absorbers, (3) excited-state quenchers, (4) peroxide decomposers, and (5) free radical scavengers; of these, it is generally believed that excited-state quenchers, peroxide decomposers, and free radical scavengers are the most effective. Research into degradation and ageing of polymers is extremely intensive and new materials are being synthesized with a pre-programmed lifetime. New stabilizers are becoming commercially available although their modes of action are sometimes not thoroughly elucidated. They target the many possible ways of polymer degradation: thermolysis, thermooxidation, photolysis, photooxidation, radiolysis etc. With the goal to increase lifetime of a particular polymeric material, two aspects of degradation are of particular importance: Storage conditions, and Addition of appropriate stabilizers. A profound knowledge of degradation mechanisms is needed to achieve the goal.
  13. 13
    Isogai, A.; Saito, T.; Fukuzumi, H. TEMPO-oxidized cellulose nanofibers. Nanoscale 2011, 3, 71– 85,  DOI: 10.1039/C0NR00583E
    Google Scholar
    13
    TEMPO-oxidized cellulose nanofibers
    Isogai, Akira; Saito, Tsuguyuki; Fukuzumi, Hayaka
    Nanoscale (2011), 3 (1), 71-85CODEN: NANOHL; ISSN:2040-3372. (Royal Society of Chemistry)
    A review on prepn. methods and fundamental characteristics of TEMPO-oxidized cellulose nanofibers (TOCN) and tensile strengths, thermal stability, and oxygen permeability of TOCN/poly(lactic acid) composite.
  14. 14
    Sirviö, J. A.; Kolehmainen, A.; Visanko, M.; Liimatainen, H.; Niinimäki, J.; Hormi, O. E. O. Strong, Self-Standing Oxygen Barrier Films from Nanocelluloses Modified with Regioselective Oxidative Treatments. ACS Appl. Mater. Interfaces 2014, 6, 14384– 14390,  DOI: 10.1021/am503659j
    Google Scholar
    14
    Strong, Self-Standing Oxygen Barrier Films from Nanocelluloses Modified with Regioselective Oxidative Treatments
    Sirvio, Juho Antti; Kolehmainen, Aleksi; Visanko, Miikka; Liimatainen, Henrikki; Niinimaki, Jouko; Hormi, Osmo E. O.
    ACS Applied Materials & Interfaces (2014), 6 (16), 14384-14390CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
    In this work, three self-standing nanocellulose films were produced from birch pulp using regioselective oxidn. and further derivatization treatments. The modified celluloses were synthesized using periodate oxidn., followed by chlorite oxidn., bisulfite addn., or reductive amination with amino acid taurine, which resulted in dicarboxylic acid cellulose (DCC), α-hydroxy sulfonic acid cellulose (HSAC), and taurine-modified cellulose (TC), resp. The nanocelluloses were fabricated by mech. disintegration using high-pressure homogenization. Mech. and barrier properties of the nanocellulose films were characterized. Two (2,2,6,6-tetramethyl-piperidin-1-yl)oxyl (TEMPO) oxidn.-based nanocellulose films were also produced, and their properties were compared to the periodate-based nanocellulose films. All of the periodate-based nanocellulose films showed high tensile strength (130-163 MPa) and modulus (19-22 GPa). Oxygen barrier properties of the films were superior to many synthetic and composite materials; in particular, the nanofibrillated DCC films had oxygen permeability as low as 0.12 cm3 μm/(m2 d kPa) at 50% relative humidity. Compared to films of TEMPO-oxidized nanocelluloses, all of the periodate-based nanocellulose films had similar or even better mech. and barrier properties, demonstrating versatility of periodate oxidn. to obtain nanocellulose films with adjustable properties. Also, for the first time, amino-acid-based cellulose modification was used in the prodn. of nanocellulose.
  15. 15
    Visanko, M.; Liimatainen, H.; Sirviö, J. A.; Mikkonen, K. S.; Tenkanen, M.; Sliz, R.; Hormi, O.; Niinimäki, J. Butylamino-functionalized cellulose nanocrystal films: barrier properties and mechanical strength. RSC Adv. 2015, 5, 15140– 15146,  DOI: 10.1039/C4RA15445B
    Google Scholar
    15
    Butylamino-functionalized cellulose nanocrystal films: barrier properties and mechanical strength
    Visanko, Miikka; Liimatainen, Henrikki; Sirvio, Juho Antti; Mikkonen, Kirsi S.; Tenkanen, Maija; Sliz, Rafal; Hormi, Osmo; Niinimaki, Jouko
    RSC Advances (2015), 5 (20), 15140-15146CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
    Cellulose nanocrystals (CNCs), which are strong, rod-like constituents of plant cellulose, are promising materials for green packaging applications as the material is capable of forming tortuous network structures with efficient barriers against outside gases. Here, a two-step procedure based on periodate oxidn. followed by reductive amination was used as a pretreatment to modify bleached birch chem. wood pulp. Individualized CNCs were obtained from three different butylamino-functionalized pulps by mech. homogenization. The fabricated CNCs were utilized to form transparent barrier films with a vacuum filtration method. All the butylamino-functionalized CNC films showed capability to resist oxygen permeability even at high relative humidity (RH 80%), and values as low as 5.9 ± 0.2 cm3 μm/m2/day/kPa were recorded for pure cellulose based film using tert-butylamino-functionalized CNCs. In addn. a barriers against water vapor permeation and dynamic vapor sorption were detd. up to relative humidities of 80 and 90%, resp. For surface characterization of the films time-dependent contact angles and surface roughness were measured. The films had good mech. characteristics with tensile strength of 105.7 ± 9.7 MPa, strain-to-failure of 6.4 ± 0.6% and a Young's modulus of 5.8 ± 0.8 GPa.
  16. 16
    Missoum, K.; Belgacem, M. N.; Bras, J. Nanofibrillated Cellulose Surface Modification: A Review. Materials 2013, 6, 1745– 1766,  DOI: 10.3390/ma6051745
    Google Scholar
    16
    Nanofibrillated Cellulose Surface Modification: A Review
    Missoum Karim; Belgacem Mohamed Naceur; Bras Julien
    Materials (Basel, Switzerland) (2013), 6 (5), 1745-1766 ISSN:1996-1944.
    Interest in nanofibrillated cellulose (NFC) has increased notably over recent decades. This bio-based nanomaterial has been used essentially in bionanocomposites or in paper thanks to its high mechanical reinforcement ability or barrier property respectively. Its nano-scale dimensions and its capacity to form a strong entangled nanoporous network have encouraged the emergence of new high-value applications. It is worth noting that chemical surface modification of this material can be a key factor to achieve a better compatibility with matrices. In order to increase the compatibility in different matrices or to add new functions, surface chemical modification of NFC appears to be the prior choice to conserve its intrinsic nanofibre properties. In this review, the authors have proposed for the first time an overview of all chemical grafting strategies used to date on nanofibrillated cellulose with focus on surface modification such as physical adsorption, molecular grafting or polymer grafting.
  17. 17
    Adudonia, K. S.; Saad, G. R.; Naguib, H. F.; Ewis, M.; Zahran, D.; Elsabee, M. Z. Surface modification of polypropylene film by grafting with vinyl monomers for the attachment of chitosan. J. Polym. Res. 2018, 25, 125,  DOI: 10.1007/s10965-018-1517-3
    Google Scholar
    There is no corresponding record for this reference.
  18. 18
    Dou, J.; Bian, H.; Yelle, D. J.; Ago, M.; Vajanto, K.; Vuorinen, T.; Zhu, J. Y. Lignin containing cellulose nanofibril production from willow bark at 80 °C using a highly recyclable acid hydrotrope. Ind. Crops Prod. 2019, 129, 15– 23,  DOI: 10.1016/j.indcrop.2018.11.033
    Google Scholar
    18
    Lignin containing cellulose nanofibril production from willow bark at 80 °C using a highly recyclable acid hydrotrope
    Dou, Jinze; Bian, Huiyang; Yelle, Daniel J.; Ago, Mariko; Vajanto, Krista; Vuorinen, Tapani; Zhu, Junyong
    Industrial Crops and Products (2019), 129 (), 15-23CODEN: ICRDEW; ISSN:0926-6690. (Elsevier B.V.)
    We conducted the first comparative exploration on lignin contg. cellulose nanofibril films prepd. alternatively from willow bark and wood using a highly recyclable acid hydrotrope, aq. p-toluenesulfonic acid, as a sustainable means for isolating the nanofibrils. The nanofibrils of willow bark were hydrophobic and produced dense films of high strength under hot pressing. The hydrophobicity resulted from condensation of the residual lignin with low mol. wt. arom. substances of the bark and hydroxymethylfurfural formed in situ from fructose that is also present in the bark.
  19. 19
    Chen, L.; Dou, J.; Ma, Q.; Li, N.; Wu, R.; Bian, H.; Yelle, D. J.; Vuorinen, T.; Fu, S.; Pan, X.; Zhu, J. Rapid and near-complete dissolution of wood lignin at ≤80 °C by a recyclable acid hydrotrope. Sci. Adv. 2017, 3, e1701735  DOI: 10.1126/sciadv.1603079
    Google Scholar
    19
    Rapid and near-complete dissolution of wood lignin at ≤80°C by a recyclable acid hydrotrope
    Chen, Liheng; Dou, Jinze; Ma, Qianli; Li, Ning; Wu, Ruchun; Bian, Huiyang; Yelle, Daniel J.; Vuorinen, Tapani; Fu, Shiyu; Pan, Xuejun; Zhu, Junyong
    Science Advances (2017), 3 (9), e1701735/1-e1701735/11CODEN: SACDAF; ISSN:2375-2548. (American Association for the Advancement of Science)
    Wereport the discovery of the hydrotropic properties of a recyclable arom. acid, p-toluenesulfonic acid (p-TsOH), for potentially low-cost and efficient fractionation of wood through rapid and near-complete dissoln. of lignin. Approx. 90% of poplar wood (NE222) lignin can be dissolved at 80°C in 20 min. Equivalent delignification using known hydrotropes, such as arom. salts, can be achieved only at 150°C or higher for more than 10 h or at 150°C for 2 h with alk. pulping. p-TsOH fractionated wood into two fractions: (i) a primarily celluloserich water-insol. solid fraction that can be used for the prodn. of high-value building blocks, such as dissolving pulp fibers, lignocellulosic nanomaterials, and/or sugars through subsequent enzymic hydrolysis; and (ii) a spent acid liquor stream contg. mainly dissolved lignin that can be easily pptd. as lignin nanoparticles by dilg. the spent acid liquor to below the minimal hydrotrope concn. Our NMR analyses of the dissolved lignin revealed that p-TsOH can depolymerize lignin via ether bond cleavage and can sep. carbohydrate-free lignin from the wood. p-TsOH has a relatively low water soly., which can facilitate efficient recovery using com. proven crystn. technol. by cooling the concd. spent acid soln. to ambient temps. to achieve environmental sustainability through recycling of p-TsOH.
  20. 20
    Rajala, S.; Siponkoski, T.; Sarlin, E.; Mettänen, M.; Vuoriluoto, M.; Pammo, A.; Juuti, J.; Rojas, O. J.; Franssila, S.; Tuukkanen, S. Cellulose Nanofibril Film as a Piezoelectric Sensor Material. ACS Appl. Mater. Interfaces 2016, 8, 15607– 15614,  DOI: 10.1021/acsami.6b03597
    Google Scholar
    20
    Cellulose Nanofibril Film as a Piezoelectric Sensor Material
    Rajala, Satu; Siponkoski, Tuomo; Sarlin, Essi; Mettanen, Marja; Vuoriluoto, Maija; Pammo, Arno; Juuti, Jari; Rojas, Orlando J.; Franssila, Sami; Tuukkanen, Sampo
    ACS Applied Materials & Interfaces (2016), 8 (24), 15607-15614CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
    Self-standing films (45 μm thick) of native cellulose nanofibrils (CNFs) were synthesized and characterized for their piezoelec. response. The surface and the microstructure of the films were evaluated with image-based anal. and SEM. The measured dielec. properties of the films at 1 kHz and 9.97 GHz indicated a relative permittivity of 3.47 and 3.38 and loss tangent tan δ of 0.011 and 0.071, resp. The films were used as functional sensing layers in piezoelec. sensors with corresponding sensitivities of 4.7-6.4 pC/N in ambient conditions. This piezoelec. response is expected to increase remarkably upon film polarization resulting from the alignment of the cellulose cryst. regions in the film. The CNF sensor characteristics were compared with those of polyvinylidene fluoride (PVDF) as ref. piezoelec. polymer. Overall, the results suggest that CNF is a suitable precursor material for disposable piezoelec. sensors, actuators, or energy generators with potential applications in the fields of electronics, sensors, and biomedical diagnostics.
  21. 21
    Mendes, J. A. S.; Prozil, S. O.; Evtuguin, D. V.; Lopes, L. P. C. Towards comprehensive utilization of winemaking residues: Characterization of grape skins from red grape pomaces of variety Touriga Nacional. Ind. Crops Prod. 2013, 43, 25– 32,  DOI: 10.1016/j.indcrop.2012.06.047
    Google Scholar
    21
    Towards comprehensive utilization of winemaking residues: Characterization of grape skins from red grape pomaces of variety Touriga Nacional
    Mendes, Joana A. S.; Prozil, Sonia O.; Evtuguin, Dmitry V.; Lopes, Luisa P. Cruz
    Industrial Crops and Products (2013), 43 (), 25-32CODEN: ICRDEW; ISSN:0926-6690. (Elsevier B.V.)
    The chem. compn. and the structural features of macromol. components from red grape skins (variety Touriga Nacional) have been evaluated. The results of chem. analyses revealed the following contents of the main constituents: cellulose (20.8%), hemicelluloses (12.5%), proteins (18.8%), tannins (13.8%), extractives sol. in dichloromethane (5.0%) and ash (7.8%). Cellulose of grape skins is typical cellulose I polymorph with a degree of crystallinity of 66.1% as assessed by X-ray scattering. The hemicelluloses were analyzed by neutral sugars anal., methylation anal. and 1D/2D 1H NMR. The water-sol. compds. (26.4%) are composed mainly of monomeric sugars (glucose and fructose) and a complex mixt. of hemicelluloses, the most abundant being pectin and acetylated glucomannan. The major part of structural polysaccharides (cellulose, xylan, xyloglucan, etc.) is embedded in cuticular layer and is poorly accessible to the acid hydrolysis. The cuticular substances contributed to ca. 8.5% of grape skins and their chem. structure has been evaluated by methanolysis. The possibility of comprehensive utilization of grape skins has been discussed.
  22. 22
    Webb, H. K.; Truong, V. K.; Hasan, J.; Fluke, C.; Crawford, R. J.; Ivanova, E. P. Roughness Parameters for Standard Description of Surface Nanoarchitecture. Scanning 2012, 34, 257– 263,  DOI: 10.1002/sca.21002
    Google Scholar
    22
    Roughness Parameters for Standard Description of Surface Nanoarchitecture
    Webb, Hayden K.; Truong, Vi Khanh; Hasan, Jafar; Fluke, Christopher; Crawford, Russell J.; Ivanova, Elena P.
    Scanning (2012), 34 (4), 257-263CODEN: SCNNDF; ISSN:0161-0457. (John Wiley & Sons, Inc.)
    The nanoarchitecture and surface roughness of metallic thin films prepd. by magnetron sputtering were analyzed to det. the topog. statistics that give the optimum description of their nanoarchitechture. Nanoscale topog. profiles were generated by performing at. force microscopy (AFM) scans of 1 μm × 1 μm areas of titanium and silver films of three different thicknesses (3 nm, 12 nm, and 150 nm). Of the titanium films, the 150-nm film had the highest av. roughness (Ra = 2.63 nm), more than four times that of the 3-nm and 12-nm titanium films. When silver films were coated on top of 150-nm titanium films, the av. roughness increased further; the 3-nm (Ra = 4.96 nm) and 150-nm (Ra = 4.65 nm) silver films av. roughnesses were approx. twice that of the 150-nm titanium film. For topog. anal., seven statistical parameters were calcd. These parameters included commonly used roughness measurements, as well as some less commonly used measurements, in order to det. which combination of parameters gave the best overall description of the nanoarchitecture of the films presented. Skewness (Rskw), surface area increase (Rsa), and peak counts (Rpc) provided the best description of horizontal surface dimensions, and in conjunction with vertical descriptors Ra and Rq gave the best characterization of surface architecture. The five roughness parameters Ra, Rq, Rskw, Rsa, and Rpc are proposed as a new std. for describing surface nanoarchitecture. SCANNING 34: 257-263, 2012. © 2012 Wiley Periodicals, Inc.
  23. 23
    Kim, H.; Ralph, J. Solution-state 2D NMR of ball-milled plant cell wall gels in DMSO-d6/pyridine-d5. Org. Biomol. Chem. 2010, 8, 576– 591,  DOI: 10.1039/B916070A
    Google Scholar
    23
    Solution-state 2D NMR of ball-milled plant cell wall gels in DMSO-d6/pyridine-d5
    Kim, Hoon; Ralph, John
    Organic & Biomolecular Chemistry (2010), 8 (3), 576-591CODEN: OBCRAK; ISSN:1477-0520. (Royal Society of Chemistry)
    NMR fingerprinting of the components of finely divided plant cell walls swelled in DMSO has been recently described. Cell wall gels, produced directly in the NMR tube with perdeutero-dimethylsulfoxide, allowed the acquisition of well resolved/dispersed 2D 13C-1H correlated soln.-state NMR spectra of the entire array of wall polymers, without the need for component fractionation. That is, without actual solubilization, and without apparent structural modification beyond that inflicted by the ball milling and ultrasonication steps, satisfactorily interpretable spectra can be acquired that reveal compositional and structural details regarding the polysaccharide and lignin components in the wall. Here, the profiling method has been improved by using a mixt. of perdeuterated DMSO and pyridine (4 : 1, vol./vol.). Adding pyridine provided not only easier sample handling because of the better mobility compared to the DMSO-d6-only system but also considerably elevated intensities and improved resoln. of the NMR spectra due to the enhanced swelling of the cell walls. This modification therefore provides a more rapid method for comparative structural evaluation of plant cell walls than is currently available. We examd. loblolly pine (Pinus taeda, a gymnosperm), aspen (Populus tremuloides, an angiosperm), kenaf (Hibiscus cannabinus, an herbaceous plant), and corn (Zea mays L., a grass, i.e., from the Poaceae family). In principle, lignin compn. (notably, the syringyl : guaiacyl : p-hydroxyphenyl ratio) can be quantified without the need for lignin isolation. Correlations for p-coumarate units in the corn sample are readily seen, and a variety of the ferulate correlations are also well resolved; ferulates are important components responsible for cell wall crosslinking in grasses. Polysaccharide anomeric correlations were tentatively assigned for each plant sample based on std. samples and various literature data. With the new potential for chemometric anal. using the 2D NMR fingerprint, this gel-state method may provide the basis for an attractive approach to providing a secondary screen for selecting biomass lines and for optimizing biomass processing and conversion efficiencies.
  24. 24
    Dou, J.; Paltakari, J.; Johansson, L.; Vuorinen, T. Novel Insight into the Separation and Composite Utilization of Sclerenchyma Fiber Bundles of Willow Bark. ACS Sustainable Chem. Eng. 2019, 7, 2964– 2970,  DOI: 10.1021/acssuschemeng.8b04001
    Google Scholar
    24
    Novel Insight into the Separation and Composite Utilization of Sclerenchyma Fiber Bundles of Willow Bark
    Dou, Jinze; Paltakari, Jouni; Johansson, Leena-Sisko; Vuorinen, Tapani
    ACS Sustainable Chemistry & Engineering (2019), 7 (3), 2964-2970CODEN: ASCECG; ISSN:2168-0485. (American Chemical Society)
    The bark from fast-growing willow crops contains long and strong sclerenchyma fiber bundles, which could potentially replace the pulp and annual plant fibers currently used to reinforce green polymer composites. Here we successfully demonstrate the isolation of fiber bundles of willow bark with a simple alkali treatment under much milder conditions than what pulp fiber sepn. requires. The fiber bundles sepd. had hydrophobic surfaces, which made them compatible with polymers, in this case with polylactic acid, without using any additives. The most hydrophobic fiber bundles of willow bark provided the strongest and toughest composites, superior to the corresponding isotropic composites of pulp and flax fibers. Integration of the fiber bundle isolation with a prior recovery of hot water extractable aroms. from the bark and further processing of the debarked willow stems into bioethanol and lignin, for example, could make the full valorization of the willow biomass feasible.
  25. 25
    Granata, A.; Argyropoulos, D. S. 2-Chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane, a Reagent for the Accurate Determination of the Uncondensed and Condensed Phenolic Moieties in Lignins. J. Agric. Food Chem. 1995, 43, 1538– 1544,  DOI: 10.1021/jf00054a023
    Google Scholar
    25
    2-Chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane, a Reagent for the Accurate Determination of the Uncondensed and Condensed Phenolic Moieties in Lignins
    Granata, Alessandro; Argyropoulos, Dimitris S.
    Journal of Agricultural and Food Chemistry (1995), 43 (6), 1538-44CODEN: JAFCAU; ISSN:0021-8561. (American Chemical Society)
    The use of 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane as a phosphitylation reagent in quant. 31P NMR anal. of the hydroxyl groups in lignins has been thoroughly examd., and an exptl. protocol recommended for spectra acquisition has been developed. Quant. anal. of six "std. lignins" gave results comparable to those obtained by other methods of anal. Excellent resoln. of the various phenolic hydroxyl environments including those present in condensed moieties was obsd. However, this was at the expense of resoln. in the aliph. hydroxyl region, where no distinction between primary, secondary, and the erythro and threo forms of the secondary hydroxyls of the β-O-4 bonds can be made.
  26. 26
    Sipponen, M. H.; Smyth, M.; Leskinen, T.; Johansson, L.; Österberg, M. All-lignin approach to prepare cationic colloidal lignin particles: stabilization of durable Pickering emulsions. Green Chem. 2017, 19, 5831– 5840,  DOI: 10.1039/C7GC02900D
    Google Scholar
    26
    All-lignin approach to prepare cationic colloidal lignin particles: stabilization of durable Pickering emulsions
    Sipponen, Mika Henrikki; Smyth, Matthew; Leskinen, Timo; Johansson, Leena-Sisko; Osterberg, Monika
    Green Chemistry (2017), 19 (24), 5831-5840CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
    Surface modification of colloidal lignin particles (CLPs), which are obtained from renewable resources, is a plausible route towards novel biomaterials. Here we show that adsorption of cationic lignin onto spherical CLPs produces pos. charged particles with tailored properties for the stabilization of Pickering emulsions. The threshold dosing of cationic lignin needed to achieve colloidally stable cationic dispersions was 4% relative to the dry wt. of CLPs. Compared to irregular kraft lignin particles or regular CLPs, cationic CLPs stabilized a broader array of durable Pickering emulsions. This all-lignin adsorption process to prep. cationic CLPs is advantageous because it minimizes the consumption of synthetic polymers, and opens new application opportunities for structurally defined nano- and microscale lignin particles.
  27. 27
    Liu, T. Y.; Chang, Y. H. Hydrolysis of proteins with p-Toluenesulfonic acid. Determination of tryptophan. J. Biol. Chem. 1971, 246, 2842– 2848,  DOI: 10.1016/S0021-9258(18)62259-8
    Google Scholar
    27
    Hydrolysis of proteins with p-toluenesulfonic acid. Determination of tryptophan
    Liu, Teh-Yung; Chang, Yi-Han
    Journal of Biological Chemistry (1971), 246 (9), 2842-8CODEN: JBCHA3; ISSN:0021-9258.
    A new procedure for anals. for tryptophan in proteins and glycoproteins utilizes p-toluenesulfonic acid as the catalyst for hydrolysis and the amino acid analyzer for the quant. estn. of tryptophan. The hydrolysis of proteins is carried out in 3N p-toluenesulfonic acid contg. 0.2% 3-(2-aminoethyl)-indole in evacuated sealed tubes at 110° for 22, 48, or 72 hr. The values of tryptophan obtained were close to the expected integral values and the recoveries of all other amino acids were comparable to those obsd. after hydrolysis with 6N HCl. Since the hydrolyzate can be placed on the ion exchange column without the prior removal of the solvent, which is required when 6N HCl is used for the hydrolysis, the present procedure is more convenient than the use of 6N HCl. This procedure, however, is not designed for the anals. of proteins that are grossly contaminated with carbohydrates, such as feeds. The limit of carbohydrate content that the present procedure can tolerate is 2.0 mg when 2-4 mg of protein are being hydrolyzed with 1.0 ml of the acid.
  28. 28
    Dou, J.; Kim, H.; Li, Y.; Padmakshan, D.; Yue, F.; Ralph, J.; Vuorinen, T. Structural Characterization of Lignins From Willow Bark and Wood. J. Agric. Food Chem. 2018, 66, 7294– 7300,  DOI: 10.1021/acs.jafc.8b02014
    Google Scholar
    28
    Structural Characterization of Lignins from Willow Bark and Wood
    Dou, Jinze; Kim, Hoon; Li, Yanding; Padmakshan, Dharshana; Yue, Fengxia; Ralph, John; Vuorinen, Tapani
    Journal of Agricultural and Food Chemistry (2018), 66 (28), 7294-7300CODEN: JAFCAU; ISSN:0021-8561. (American Chemical Society)
    Understanding the chem. structure of lignin in willow bark is an indispensable step to design how to sep. its fiber bundles. The whole cell wall and enzyme lignin prepns. sequentially isolated from ball-milled bark, inner bark, and wood were comparatively investigated by NMR spectroscopy and three classical degradative methods, i.e., alk. nitrobenzene oxidn., derivatization followed by reductive cleavage, and anal. thioacidolysis. All results demonstrated that the guaiacyl (G) units were predominant in the willow bark lignin over syringyl (S) and minor p-hydroxyphenyl (H) units. Moreover, the monomer yields and S/G ratio rose progressively from bark to inner bark and wood, indicating that lignin may be more condensed in bark than in other tissues. Addnl., major interunit linkage substructures (β-aryl ethers, phenylcoumarins, and resinols) together with cinnamyl alc. end groups were relatively quantitated by two-dimensional NMR spectroscopy. Bark and inner bark were rich in pectins and proteins, which were present in large quantities and also in the enzyme lignin prepns.
  29. 29
    Kim, H.; Padmakshan, D.; Li, Y.; Rencoret, J.; Hatfield, R. D.; Ralph, J. Characterization and Elimination of Undesirable Protein Residues in Plant Cell Wall Materials for Enhancing Lignin Analysis by Solution-State Nuclear Magnetic Resonance Spectroscopy. Biomacromolecules 2017, 18, 4184– 4195,  DOI: 10.1021/acs.biomac.7b01223
    Google Scholar
    29
    Characterization and Elimination of Undesirable Protein Residues in Plant Cell Wall Materials for Enhancing Lignin Analysis by Solution-State Nuclear Magnetic Resonance Spectroscopy
    Kim, Hoon; Padmakshan, Dharshana; Li, Yanding; Rencoret, Jorge; Hatfield, Ronald D.; Ralph, John
    Biomacromolecules (2017), 18 (12), 4184-4195CODEN: BOMAF6; ISSN:1525-7797. (American Chemical Society)
    Protein polymers exist in every plant cell wall prepn., and they interfere with lignin characterization and quantification. Here, we report the structural characterization of the residual protein peaks in 2D NMR spectra in corn cob and kenaf samples and note that arom. amino acids are ubiquitous and evident in spectra from various other plants and tissues. The arom. correlations from amino acid residues were identified and assigned as phenylalanine and tyrosine. Phenylalanine's 3/5 correlation peak is superimposed on the peak from typical lignin p-hydroxyphenyl (H-unit) structures, causing an overestimation of the H units. Protein contamination also occurs when using cellulases to prep. enzyme lignins from virtually protein-free wood samples. We used a protease to remove the protein residues from the ball-milled cell walls, and we were able to reveal H-unit structures in lignins more clearly in the 2D NMR spectra, providing a better basis for their estn.
  30. 30
    Dou, J.; Xu, W.; Koivisto, J. J.; Mobley, J. K.; Padmakshan, D.; Kögler, M.; Xu, C.; Willför, S.; Ralph, J.; Vuorinen, T. Characteristics of Hot Water Extracts from the Bark of Cultivated Willow (Salix sp.). ACS Sustainable Chem. Eng. 2018, 6, 5566– 5573,  DOI: 10.1021/acssuschemeng.8b00498
    Google Scholar
    30
    Characteristics of Hot Water Extracts from the Bark of Cultivated Willow (Salix sp.)
    Dou, Jinze; Xu, Wenyang; Koivisto, Jari J.; Mobley, Justin K.; Padmakshan, Dharshana; Kogler, Martin; Xu, Chunlin; Willfor, Stefan; Ralph, John; Vuorinen, Tapani
    ACS Sustainable Chemistry & Engineering (2018), 6 (4), 5566-5573CODEN: ASCECG; ISSN:2168-0485. (American Chemical Society)
    Willow bark is a rich source of heterogeneous polyphenolic compds. and a potential feedstock for biorefinery processes aiming at chems. and fiber prodn. Here mild hot water treatment of willow hybrid Karin was studied to find a practical means of isolating its non-cell-wall components for their utilization in a willow biorefinery proposed to aid valorization of the willow biomass. A short aq. treatment of the bark at 80 °C liberated the ext. in >20% yield under unpressurized conditions. The ext. was characterized using mainly gas chromatog.-mass spectrometry and one- and two-dimensional NMR techniques. Authentic analytes were applied to confirm the identification and quantification of the main components that were picein, (+)-catechin, triandrin, glucose, and fructose. Fructose was converted into 5-hydroxymethylfurfural (HMF) in an acidic treatment which led to its condensation with the phenolic components and formation of a recalcitrant ppt. that should be avoided.
  31. 31
    Kesari, K. K.; Dhasmana, A.; Shandilya, S.; Prabhakar, N.; Shaukat, A.; Dou, J.; Rosenholm, J. M.; Vuorinen, T.; Ruokolainen, J. Plant-Derived Natural Biomolecule Picein Attenuates Menadione Induced Oxidative Stress on Neuroblastoma Cell Mitochondria. Antioxidants 2020, 9, 552  DOI: 10.3390/antiox9060552
    Google Scholar
    31
    Plant-derived natural biomolecule picein attenuates menadione induced oxidative stress on neuroblastoma cell mitochondria
    Kesari, Kavindra Kumar; Dhasmana, Anupam; Shandilya, Shruti; Prabhakar, Neeraj; Shaukat, Ahmed; Dou, Jinze; Rosenholm, Jessica M.; Vuorinen, Tapani; Ruokolainen, Janne
    Antioxidants (2020), 9 (6), 552CODEN: ANTIGE; ISSN:2076-3921. (MDPI AG)
    Several bioactive compds. are in use for the treatment of neurodegenerative disorders, such as Alzheimer's and Parkinson's disease. Historically, willow (salix sp.) bark has been an important source of salisylic acid and other natural compds. with anti-inflammatory, antipyretic and analgesic properties. Among these, picein isolated from hot water ext. of willow bark, has been found to act as a natural secondary metabolite antioxidant. The aim of this study was to investigate the unrevealed pharmacol. action of picein. In silico studies were utilized to direct the investigation towards the neuroprotection abilities of picein. Our in vitro studies demonstrate the neuroprotective properties of picein by blocking the oxidative stress effects, induced by free radical generator 2-methyl-1,4-naphthoquinone (menadione, MQ), in neuroblastoma SH-SY5Y cells. Several oxidative stress-related parameters were evaluated to measure the protection for mitochondrial integrity, such as mitochondrial superoxide prodn., mitochondrial activity (MTT), reactive oxygen species (ROS) and live-cell imaging. A significant increase in the ROS level and mitochondrial superoxide prodn. were measured after MQ treatment, however, a subsequent treatment with picein was able to mitigate this effect by decreasing their levels. Addnl., the mitochondrial activity was significantly decreased by MQ exposure, but a follow-up treatment with picein recovered the normal metabolic activity. In conclusion, the presented results demonstrate that picein can significantly reduce the level of MQ-induced oxidative stress on mitochondria, and thereby plays a role as a potent neuroprotectant.
  32. 32
    Panossian, A.; Hamm, R.; Wikman, G.; Efferth, T. Mechanism of action of Rhodiola, salidroside, tyrosol and triandrin in isolated neuroglial cells: An interactive pathway analysis of the downstream effects using RNA microarray data. Phytomedicine 2014, 21, 1325– 1348,  DOI: 10.1016/j.phymed.2014.07.008
    Google Scholar
    32
    Mechanism of action of Rhodiola, salidroside, tyrosol and triandrin in isolated neuroglial cells: An interactive pathway analysis of the downstream effects using RNA microarray data
    Panossian, Alexander; Hamm, Rebecca; Wikman, Georg; Efferth, Thomas
    Phytomedicine (2014), 21 (11), 1325-1348CODEN: PYTOEY; ISSN:0944-7113. (Elsevier GmbH)
    The aim of this study was to identify the targets (genes, interactive signaling pathways, and mol. networks) of Rhodiola rosea ext. in isolated neuroglia cells and to predict the effects of Rhodiola ext. on cellular functions and diseases. In addn., the potential mechanism of action of Rhodiola rosea ext. was elucidated, and the "active principle" among the three isolated constituents (salidroside, triandrin, and tyrosol) was identified. Gene expression profiling was performed using the T98G human neuroglia cell line after treatment with the Rhodiola rosea SHR-5 ext. and several of its individual constituents (salidroside, triandrin and tyrosol). An interactive pathway anal. of the downstream effects was performed using datasets contg. significantly up- and down-regulated genes, and the effects on cellular functions and diseases were predicted. In total, the expression of 1062 genes was deregulated by the Rhodiola ext. (631 analyzed, 336 - up-regulated, 295 - down-regulated), and 1052, 1062, and 1057 genes were deregulated by salidroside, triandrin, and tyrosol, resp. The anal. of the downstream effects shows that the most significant effects of Rhodiola are assocd. with cardiovascular (72 deregulated genes), metabolic (63 genes), gastrointestinal (163 genes), neurol. (95 genes), endocrine (60 genes), behavioral (50 genes), and psychol. disorders (62 genes). The most significantly affected canonical pathways across the entire dataset, which contains the 1062 genes deregulated by Rhodiola, were the following: (a) communication between innate and adaptive immune cells, (b) eNOS signaling, (c) altered T and B cell signaling in rheumatoid arthritis, (d) axonal guidance signaling, (e) G-protein coupled receptor signaling, (f) glutamate receptor signaling, (g) ephrin receptor signaling, (h) cAMP-mediated, and (i) atherosclerosis signaling pathways. Genes assocd. with behavior and behavioral diseases were identified within intracellular signaling pathways (d) through (h). The anal. of the downstream effects predicted decreases in emotional and aggressive behavior, which corroborates the results from preclin. and clin. studies of the use of Rhodiola for the treatment of depression and anxiety. Of the 17 genes that regulate emotional behavior, nine exhibit expression patterns that are consistent with decreases in emotional behavior (z-score -2.529), and all five relevant genes are expressed in a manner consistent with decreases in aggressive behavior (z-score -2.197). A decrease in seizures and infarct sizes and an increase in the chemotaxis of cells were predicted to accompany the decrease in emotional and aggressive behaviors. Rhodiola exhibits a multi-targeted effect on transcription to regulate the cellular response, affecting the various signaling pathways and mol. networks assocd. with beneficial effects on emotional behavior, particularly aggressive behavior, and with psychol., neurol., cardiovascular, metabolic, endocrine, and gastrointestinal disorders. Each of the purified compds. has its own pharmacol. profile, which is both similar to and different from that of the total Rhodiola ext. In general, several compds. contribute to the specific cellular or/and physiol. function of the ext. in various diseases.
  33. 33
    Dou, J.; Heinonen, J.; Vuorinen, T.; Xu, C.; Sainio, T. Chromatographic recovery and purification of natural phytochemicals from underappreciated willow bark water extracts. Sep. Purif. Technol. 2021, 261, 118247  DOI: 10.1016/j.seppur.2020.118247
    Google Scholar
    33
    Chromatographic recovery and purification of natural phytochemicals from underappreciated willow bark water extracts
    Dou, Jinze; Heinonen, Jari; Vuorinen, Tapani; Xu, Chunlin; Sainio, Tuomo
    Separation and Purification Technology (2021), 261 (), 118247CODEN: SPUTFP; ISSN:1383-5866. (Elsevier B.V.)
    Willow (Salicaceae) bark contains a variety of antioxidant phytochems. depending mainly on the hybrid. In this study, hot water extn. of willow bark was coupled with a sequential preparative scale chromatog. to purify the crude exts. to a well-sepd. and highly concd. phytochem. fraction. The pre-equilibrated hydrophilic weak cation exchange resins (with acrylic matrix in Na+ ions form) achieved a good sepn. of phytochems. from monosaccharide fractions. Secondly, the individual phytochem. can be purified based on their size and hydrophobicity differences, using gel permeation chromatog. and adsorption column chromatog. Surprisingly, the G-types of sephadex demonstrated an efficient sepn. of not only monosaccharides but a complete sepn. between (+)-catechin and triandrin. Picein and salicin can be further sepd. according to their hydrophobicity differences. The purified compds. can be quickly quantified using high performance liq. chromatog., gas chromatog. and high-performance anion-exchange chromatog. The purified picein and triandrin were characterized by one- and two-dimensional NMR spectroscopy techniques. Addnl., the authentic compds. were applied to confirm the identification, quantification and purity. The technique described here might be a fast, economical, and highly efficient way in the large-scale isolation and purifn. of the phytochem. compds. from willow bark.
  34. 34
    Sinitsya, A.; Čopíkovά, J.; Pavlíkovά, H. 13C CP/MAS NMR Spectroscopy in the Analysis of Pectins. J. Carbohydr. Chem. 1998, 17, 279– 292,  DOI: 10.1080/07328309808002328
    Google Scholar
    34
    Carbon-13 CP/MAS NMR spectroscopy in the analysis of pectins
    Sinitsya, Andriy; Copikova, Jana; Pavlikova, Helena
    Journal of Carbohydrate Chemistry (1998), 17 (2), 279-292CODEN: JCACDM; ISSN:0732-8303. (Marcel Dekker, Inc.)
    Carbon-13 CP/MAS NMR spectra of powd. com. pectin (I) samples were recorded and interpreted. NMR spectral results were applied for the calcn. of galacturonic acid (II) content, degrees of methylation (DM) and acetylation (DA). In most cases NMR values from II and DM agreed with values obtained by conventional methods, i.e., photometry and HPLC. The detn. of DA using NMR data was successful only in the case of sugar beet I with high acetyl content. The C-6 carbon region was studied in detail, and the chem. shift and the shape of peaks in this region were strongly influenced by the ratio of uronic carboxyl forms. Correlation between C-6 carbon chem. shift and DM values for I samples in their protonated form was evaluated.
  35. 35
    Koch, H.; Pein, J. Condensation Reactions Between Phenol, Formaldehyde and 5-Hydroxymethylfurfural, Formed as Intermediate in the Acid Catalyzed Dehydration of Starchy Products. Polym. Bull. 1985, 13, 525– 532,  DOI: 10.1007/BF00263474
    Google Scholar
    35
    Condensation reactions between phenol, formaldehyde and 5-hydroxymethylfurfural, formed as intermediate in the acid catalyzed dehydration of starchy products
    Koch, Helmut; Pein, Joachim
    Polymer Bulletin (Berlin, Germany) (1985), 13 (6), 525-32CODEN: POBUDR; ISSN:0170-0839.
    The incorporation of starch [9005-25-8] hydrolyzates in phenolic resins of the novolak and resol type via intermediate acid catalyzed dehydration to 5-hydroxymethylfurfural (I) was investigated. The course of the reaction was monitored by carbon-13-NMR and IR spectroscopy. Because of the formation of I-phenol condensates, savings of up to 40% phenol and 50% HCHO (by wt.) are possible in comparison to com. resins. Besides maintenance of essential property profiles, addnl. benefits may be achieved with respect to faster curing and lower amts. of free monomers.
  36. 36
    Lopes, M. H.; Gil, A. M.; Silvestre, A. J. D.; Neto, C. P. Composition of Suberin Extracted upon Gradual Alkaline Methanolysis of Quercus suber L. Cork. J. Agric. Food Chem. 2000, 48, 383– 391,  DOI: 10.1021/jf9909398
    Google Scholar
    36
    Composition of Suberin Extracted upon Gradual Alkaline Methanolysis of Quercus suber L. Cork
    Lopes, Marta H.; Gil, Ana M.; Silvestre, Armando J. D.; Pascoal Neto, Carlos
    Journal of Agricultural and Food Chemistry (2000), 48 (2), 383-391CODEN: JAFCAU; ISSN:0021-8561. (American Chemical Society)
    The monomeric compn. of suberin exts. obtained by gradual alk. methanolysis of Quercus suber cork was detd. by gas chromatog.-mass spectrometry (GC-MS). Results show that 1-alkanols and alkanoic and α,ω-alkanedioic acids are preferentially removed upon mild alk. conditions, whereas mid-chain-modified ω-hydroxyalkanoic acids are preferentially removed under stronger alk. conditions. Satd. ω-hydroxyalkanoic acids are found to be abundant in all suberin exts. These results are consistent with two distinct suberin fractions with different locations in cork cell walls and/or esterification degrees. It is proposed that these fractions correlate with the two main suberin peaks in the solid state 13C NMR spectra of cork and suberin exts. Quant. GC-MS anal. showed that suberin monomers comprise ∼30% (wt./wt.) of the suberin exts., the remaining comprising nonvolatile structures with high Mn values, as measured by vapor pressure osmometry. The presence of a large fraction of high mol. wt. aliph. structures in suberin exts. is supported by the corresponding NMR spectra.
  37. 37
    Rojo, E.; Peresin, M. S.; Sampson, W. W.; Hoeger, I. C.; Vartiainen, J.; Laine, J.; Rojas, O. J. Comprehensive elucidation of the effect of residual lignin on the physical, barrier, mechanical and surface properties of nanocellulose films. Green Chem. 2015, 17, 1853– 1866,  DOI: 10.1039/C4GC02398F
    Google Scholar
    37
    Comprehensive elucidation of the effect of residual lignin on the physical, barrier, mechanical and surface properties of nanocellulose films
    Rojo, Ester; Peresin, Maria Soledad; Sampson, William W.; Hoeger, Ingrid C.; Vartiainen, Jari; Laine, Janne; Rojas, Orlando J.
    Green Chemistry (2015), 17 (3), 1853-1866CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
    We elucidate the effect of residual lignin on the interfacial, phys. and mech. properties of lignocellulose nanofibrils (LCNF) and resp. nanopapers. Fibers contg. ∼0, 2, 4, and 14 wt% residual lignin were microfluidized into LCNF aq. suspensions and were processed into dry films (nanopapers). A systematic decrease in fibril diam. with increasing residual lignin was obsd. upon fibrillation, consistent with the radical scavenging ability of the lignin that results in better cell wall deconstruction. The stiff nature of the lignin-contg. fibrils made them less able to conform during filtration and improved extensively dewatering, owing to a more open structure. However, the softening of the lignin during hot-pressing of the nanopapers and its amorphous nature enabled a binding effect, filling the voids between the nanofibers (thus reducing the no. of micropores) and making the surface of the nanopapers smoother. The interfacial free energy of interaction changed drastically with the increased lignin content: the corresponding water contact angles were 35° and 78° for the lignin-free and for the (14%) lignin-contg. nanopaper, resp., revealing the increase in hydrophobicity. Together with the significantly less porous structure of LCNF nanopapers, lower water absorbency was obsd. with increased lignin content. Lignin in the nanopapers reduced the oxygen permeability by up to 200-fold. Water vapor permeability, in turn, did not correlate linearly with lignin content but depended most significantly on material d. The tensile strength, modulus, and strain for the LCNF nanopapers were found to be in the range 116-164 MPa, 10.5-14.3 GPa, and 1.7-3.5%, resp. To a good degree of approxn., these mech. properties were rather insensitive to lignin content and comparable to those of nanopapers derived from fully bleached CNF. While it might be expected that lignin interferes in hydrogen bonding between fibrils, this was apparently counteracted by the uniform distribution of lignin seemingly aiding stress-transfer between fibrils and thus preserving mech. properties. Overall, LCNF is demonstrated to be a suitable precursor of nanopaper, esp. when reduced polarity and low hydrophilicity are desirable in related bio-products.
  38. 38
    Rindlav-Westling, Å.; Stading, M.; Hermansson, A.; Gatenholm, P. Structure, mechanical and barrier properties of amylose and amylopectin films. Carbohydr. Polym. 1998, 36, 217– 224,  DOI: 10.1016/S0144-8617(98)00025-3
    Google Scholar
    38
    Structure, mechanical and barrier properties of amylose and amylopectin films
    Rindlav-Westling, Asa; Stading, Mats; Hermansson, Anne-Marie; Gatenholm, Paul
    Carbohydrate Polymers (1998), 36 (2/3), 217-224CODEN: CAPOD8; ISSN:0144-8617. (Elsevier Science Ltd.)
    The effect of film formation conditions on structure, mech. properties, and barrier properties of amylose (I) and amylopectin (II) films was studied. The films were prepd. by soln.-gel-casting of I and II from potato, with or without the addn. of glycerol (III) as plasticizer. Transmission electron micrographs showed that the network structure characteristic for the I gel was also found in the film state. The I films without III plasticization exhibited a relatively high degree of B-type crystallinity, as revealed by wide-angle x-ray diffraction, whereas the unplasticized II films were amorphous. Although the addn. of III did not affect the crystallinity of the I films, III-plasticized II formed B-type crystallinity, and the degree of crystallinity was dependent on the air humidity during film formation. The degree of crystallinity affected the mech. properties of the II films, whereas the mech. properties of the I films were influenced by the network microstructure. O and water vapor permeabilities were dependent neither on the degree of crystallinity in the films nor on the network structure.
  39. 39
    Miller, K. S.; Krochta, J. M. Oxygen and aroma barrier properties of edible films: A review. Trends Food Sci. Technol. 1997, 8, 228– 237,  DOI: 10.1016/S0924-2244(97)01051-0
    Google Scholar
    39
    Oxygen and aroma barrier properties of edible films: a review
    Miller, K. S.; Krochta, J. M.
    Trends in Food Science & Technology (1997), 8 (7), 228-237CODEN: TFTEEH; ISSN:0924-2244. (Elsevier)
    A review with 73 refs. Interest in maintaining food quality while reducing packaging waste has encouraged the exploration of the oxygen and aroma transport properties of edible films. This review article introduces the theor. basis for oxygen and aroma barrier property detn. and presents a brief historical perspective of the development of barrier polymers. The effects of structure and compn. on mass transport in edible films are examd. and compared with those of the more thoroughly investigated synthetic polymers. A survey of edible film oxygen and aroma barrier research is presented; areas requiring addnl. investigation are suggested, for applications as well as basic research.
  40. 40
    Shimizu, M.; Saito, T.; Isogai, A. Water-resistant and high oxygen-barrier nanocellulose films with interfibrillar cross-linkages formed through multivalent metal ions. J. Membr. Sci. 2016, 500, 1– 7,  DOI: 10.1016/j.memsci.2015.11.002
    Google Scholar
    40
    Water-resistant and high oxygen-barrier nanocellulose films with interfibrillar cross-linkages formed through multivalent metal ions
    Shimizu, Michiko; Saito, Tsuguyuki; Isogai, Akira
    Journal of Membrane Science (2016), 500 (), 1-7CODEN: JMESDO; ISSN:0376-7388. (Elsevier B.V.)
    Once-dried 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibril (TOCN) films with sodium carboxylate groups (TOCN-COONa) were soaked in aq. MgCl2, CaCl2, AlCl3 and FeCl3 solns. to change the counterion to TOCNs-COOM films (M: metal ion). Dry TOCN-COOM films had high Young's moduli (11-20 GPa) and tensile strength (170-280 MPa). In particular, the wet TOCN films with aluminum and iron (III) carboxylates had high Young's moduli and tensile strengths of ∼3 GPa and 30-40 MPa, resp., even at water contents of ∼470%. Moreover, the dry TOCN films with calcium and aluminum carboxylates had extremely low oxygen permeabilities of 0.08 and 0.15 mL μm m-2 day-1 kPa-1, resp., even at 80% relative humidity, which are outstanding values compared to those of other films reported previously. These results are explained in terms of the high water resistance of the films, which is caused by the formation of interfibrillar crosslinkages through multivalent metal ions.
  41. 41
    Medina Jaramillo, C.; Seligra, P. G.; Goyanes, S.; Bernal, C.; Famά, L. Biofilms based on cassava starch containing extract of yerba mate as antioxidant and plasticizer. Starch 2015, 67, 780– 789,  DOI: 10.1002/star.201500033
    Google Scholar
    41
    Biofilms based on cassava starch containing extract of yerba mate as antioxidant and plasticizer
    Medina Jaramillo, Carolina; Gonzalez Seligra, Paula; Goyanes, Silvia; Bernal, Celina; Fama, Lucia
    Starch/Staerke (2015), 67 (9-10), 780-789CODEN: STARDD; ISSN:0038-9056. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Cassava starch based films contg. different concns. of yerba mate ext. as antioxidant (0, 5, and 20%) were prepd. by casting. The effect of the incorporation of the ext. on the antioxidant activity, structure, and physicochem. properties of the biofilms was evaluated. Significant antioxidant capacity in the films with yerba mate ext. was obtained, esp. in the materials contg. 5% of the additive. The surface roughness and contact angle of the systems contg. the ext. increased, indicating hydrophobic behavior of the films surface when the additive was used. This was also confirmed by water vapor permeability and water content results. The incorporation of yerba mate ext. led to an important improvement in the elasticity of the biofilms, as well as to a shift of the relaxations assocd. with the glycerol-rich and starch-rich phases to lower temp. values, revealing a typical behavior of a plasticized film. The relevant antioxidant and plasticizing effects of yerba mate ext. on cassava starch films make them promising to be used as coatings or packaging in the food industry.
  42. 42
    Baumberger, S.; Lapierre, C.; Monties, B. Utilization of Pine Kraft Lignin in Starch Composites: Impact of Structural Heterogeneity. J. Agric. Food Chem. 1998, 46, 2234– 2240,  DOI: 10.1021/jf971067h
    Google Scholar
    42
    Utilization of Pine Kraft Lignin in Starch Composites: Impact of Structural Heterogeneity
    Baumberger, S.; Lapierre, C.; Monties, B.
    Journal of Agricultural and Food Chemistry (1998), 46 (6), 2234-2240CODEN: JAFCAU; ISSN:0021-8561. (American Chemical Society)
    To elucidate the effect of lignin structure on the properties of lignin-starch composites, an industrial pine kraft lignin sample was fractionated by sequential extn. with org. solvents. Three fractions were obtained with different carbohydrate contents, IR spectra, and mol. size distributions. In addn., an in-depth structural investigation was performed by GC-MS analyses of the low-mol. wt. phenolics occurring in the native fractions or obtained by thioacidolysis. The properties of the lignin-starch composites made from pine kraft lignin or its fractions were evaluated, as compared to ref. starch films. Although present in small quantities, the low-mol. wt. fraction isolated from pine kraft lignin was obsd. to have a key role in the mech. properties of the films, mainly as a starch plasticizer.
  43. 43
    Espinosa, E.; Bascón-Villegas, I.; Rosal, A.; Pérez-Rodríguez, F.; Chinga-Carrasco, G.; Rodríguez, A. PVA/(ligno)nanocellulose biocomposite films. Effect of residual lignin content on structural, mechanical, barrier and antioxidant properties. Int. J. Biol. Macromol. 2019, 141, 197– 206,  DOI: 10.1016/j.ijbiomac.2019.08.262
    Google Scholar
    43
    PVA/(ligno)nanocellulose biocomposite films. Effect of residual lignin content on structural, mechanical, barrier and antioxidant properties
    Espinosa, Eduardo; Bascon-Villegas, Isabel; Rosal, Antonio; Perez-Rodriguez, Fernando; Chinga-Carrasco, Gary; Rodriguez, Alejandro
    International Journal of Biological Macromolecules (2019), 141 (), 197-206CODEN: IJBMDR; ISSN:0141-8130. (Elsevier B.V.)
    Nanocelluloses with and without residual lignin were isolated from wheat straw. In addn., the effect of TEMPO-mediated oxidn. on the prodn. of lignin-contg. nanocellulose was studied. The different nanocelluloses were used as reinforcing agent in poly(vinyl alc.) films. The morphol., crystallinity, surface microstructure, barrier properties, light transmittance, mech. and antioxidant properties were evaluated. The translucency of films was reduced by the addn. of nanocellulose, however, the ability to block UV-light increased from 10% for PVA to >50% using lignin-contg. nanocellulose, and 30% for lignin-free samples. The mech. properties increased considerably, however, for loads higher than 5% a neg. trend was obsd. presumptively due to a clustering of nanocellulose components in PVA matrix. The barrier properties of the films were improved with the use of nanocellulose, esp. at small amts. (1-3%). The antioxidant capacity of films was increased up to 10% using lignin-contg. nanocellulose compared to 4.7% using PVA.
  44. 44
    De Simone, O. D.; Haase, K.; Müller, E.; Junk, W. J.; Hartmann, K.; Schreiber, L.; Schmidt, W. Apoplasmic Barriers and Oxygen Transport Properties of Hypodermal Cell Walls in Roots from Four Amazonian Tree Species. Plant Physiol. 2003, 132, 206– 217,  DOI: 10.1104/pp.102.014902
    Google Scholar
    44
    Apoplasmic barriers and oxygen transport properties of hypodermal cell walls in roots from four Amazonian tree species
    De Simone, Oliviero; Haase, Karen; Muller, Ewald; Junk, Wolfgang J.; Hartmann, Klaus; Schreiber, Lukas; Schmidt, Wolfgang
    Plant Physiology (2003), 132 (1), 206-217CODEN: PLPHAY; ISSN:0032-0889. (American Society of Plant Biologists)
    The formation of suberized and lignified barriers in the exodermis is suggested to be part of a suite of adaptations to flooded or waterlogged conditions, adjusting transport of solutes and gases in and out of roots. In this study, the compn. of apoplasmic barriers in hypodermal cell walls and oxygen profiles in roots and the surrounding medium of four Amazon tree species that are subjected to long-term flooding at their habitat was analyzed. In hypodermal cell walls of the deciduous tree Crateva benthami, suberization is very weak and dominated by monoacids, 2-hydroxy acids, and ω-hydroxycarboxylic acids. This species does not show any morphol. adaptations to flooding and overcomes the aquatic period in a dormant state. Hypodermal cells of Tabernaemontana juruana, a tree which is able to maintain its leaf system during the aquatic phase, are characterized by extensively suberized walls, incrusted mainly by the unsatd. C18 ω-hydroxycarboxylic acid and the α,ω-dicarboxylic acid analogon, known as typical suberin markers. Two other evergreen species, Laetia corymbulosa and Salix martiana, contained 3- to 4-fold less aliph. suberin in the exodermis, but more than 85% of the arom. moiety of suberin are composed of para-hydroxybenzoic acid, suggesting a function of suberin in pathogen defense. No major differences in the lignin content among the species were obsd. Detn. of oxygen distribution in the roots and rhizosphere of the four species revealed that radial loss of oxygen can be effectively restricted by the formation of suberized barriers but not by lignification of exodermal cell walls.
  45. 45
    Korpinen, R. I.; Kilpeläinen, P.; Sarjala, T.; Nurmi, M.; Saloranta, P.; Holmbom, T.; Koivula, H.; Mikkonen, K. S.; Willför, S.; Saranpää, P. T. The Hydrophobicity of Lignocellulosic Fiber Network Can Be Enhanced with Suberin Fatty Acids. Molecules 2019, 24, 4391  DOI: 10.3390/molecules24234391
    Google Scholar
    45
    The hydrophobicity of lignocellulosic fiber network can be enhanced with suberin fatty acids
    Korpinen, Risto I.; Kilpelainen, Petri; Sarjala, Tytti; Nurmi, Maristiina; Saloranta, Pauliina; Holmbom, Thomas; Koivula, Hanna; Mikkonen, Kirsi S.; Willfor, Stefan; Saranpaa, Pekka T.
    Molecules (2019), 24 (23), 4391CODEN: MOLEFW; ISSN:1420-3049. (MDPI AG)
    Suberin fatty acids were extd. from outer bark of Silver birch (Betula pendula Roth.) using an isopropanolic sodium hydroxide soln. Lab. sheets composed of lignocellulosic fiber networks were prepd. from unbleached and unrefined softwood kraft pulp and further impregnated with suberin fatty acid monomers and cured with maleic anhydride in ethanol soln. The treatment resulted in hydrophobic surfaces, in which the contact angles remained over 120 degrees during the entire measurement. The fiber network also retained its water vapor permeability and enhanced fiber-fiber bonding resulted in improved tensile strength of the sheets. SEM (SEM) images revealed that the curing agent, together with suberin fatty acids, was evenly distributed on the fiber surfaces and smoothing occurred over the wrinkled microfibrillar structure. High concns. of the curing agent resulted in globular structures contg. betulinol derivates as revealed with time-of-flight secondary ion mass spectrometry (ToF-SIMS). Also, the larger amt. of suberin fatty acid monomers slightly impaired the optical properties of sheets.
  46. 46
    Liu, X.; Wang, J.; Li, S.; Zhuang, X.; Xu, Y.; Wang, C.; Chu, F. Preparation and properties of UV-absorbent lignin graft copolymer films from lignocellulosic butanol residue. Ind. Crops Prod. 2014, 52, 633– 641,  DOI: 10.1016/j.indcrop.2013.11.036
    Google Scholar
    46
    Preparation and properties of UV-absorbent lignin graft copolymer films from lignocellulosic butanol residue
    Liu, Xiaohuan; Wang, Jifu; Li, Shouhai; Zhuang, Xiaowei; Xu, Yuzhi; Wang, Chunpeng; Chu, Fuxiang
    Industrial Crops and Products (2014), 52 (), 633-641CODEN: ICRDEW; ISSN:0926-6690. (Elsevier B.V.)
    The aim of this study was to develop economically UV-absorbent and visible-transparent films. For this purpose, lignin was selected because of its strong UV absorbing property. Lignocellulosic butanol residue, as the byproduct of lignocellulosic butanol prodn., is rich in biobutanol lignin (BBL). Herein, BBL was modified with acryloyl chloride and then copolymd. with Bu acrylate (BA) and Me methacrylate (MMA) by free-radical polymn. The chem. structure of poly(BA-co-MMA) chains was identifiable by 1H NMR and 13C NMR spectroscopies, combined with UV-visible spectra to confirm the existence of the arom. groups that are attributed to BBL in the copolymer. This provided evidence that a BBL graft copolymer was successfully synthesized. The optical, photo-stability, chem. resistance, thermal and mech. properties of the copolymer were evaluated. The copolymer film can absorb 96.2% of UV light, while allowing 70% or higher transmittance in the visible spectrum when the surface concn. of BBL-AC was 240U+03BCg cm-2. In addn., the copolymer film retained excellent absorption capacity in the UV region and high transparency in the visible light region after 75 min continuous UV-irradn. or when heated at 100U+00B0C, rendering it potential to use as a UV-absorbent film. The copolymer exhibited good chem. resistance, thermal and mech. properties compared with pure poly(BA-co-MMA). This strategy not only provides a novel approach for UV-absorbent films but also greatly extends the comprehensive utilization of BBL.
  47. 47
    Gierer, J.; Lin, S. Y. Photodegradation of lignin. A contribution to the mechanism of chromophore formation. Sven. Papperstidn. 1972, 75, 233– 237
    Google Scholar
    47
    Photodegradation of lignin. Mechanism of chromophore formation
    Gierer, Josef; Lin, Stephen Y.
    Svensk Papperstidning (1972), 75 (7), 233-9CODEN: SVPAAE; ISSN:0283-6831.
    The photochem. cleavage of phenacyl aryl ether linkages is examd., and the significance of this reaction in the light-induced discoloration and degradation of lignin is discussed. Lignin is stabilized by the redn. or epoxidation of carbonyl groups and the etherification of phenolic hydroxyls.

Cited By

Click to copy section linkSection link copied!
Citation Statements
Explore this article's citation statements on scite.ai
powered by  Scite

This article is cited by 22 publications.

  1. Tia Lohtander, Tetyana Koso, Ngoc Huynh, Tuomo Hjelt, Marie Gestranius, Alistair W. T. King, Monika Österberg, Suvi Arola. Bioactive Fiber Foam Films from Cellulose and Willow Bark Extract with Improved Water Tolerance. ACS Omega 2024, 9 (7) , 8255-8265. https://doi.org/10.1021/acsomega.3c08906
  2. Zu-Guo Yang, Fan Gao, Ji-Xiang Guo, Qiu-Ying Gao, Yan-Yan Xu, Huan Yang, Zhi-Xiang Xu, Li-jian Leng. Improving temperature and salinity tolerance of polymer gels by modifying with lignin-containing nanocellulose. Fuel 2025, 384 , 134019. https://doi.org/10.1016/j.fuel.2024.134019
  3. Pati Kemala, Arief Heru Prianto, Antonio Di Martino, Rinaldi Idroes, Sehrish Javaid, Lee Seng Hua, Widya Fatriasari. Valorization of lignin as an active agent in sustainable agriculture: A review. Journal of Industrial and Engineering Chemistry 2025, 312 https://doi.org/10.1016/j.jiec.2025.03.001
  4. Xinyu Wu, Hailan Lian, Changlei Xia, Junqian Deng, Xiaoyu Li, Changhang Zhang. Mechanistic insights and applications of lignin-based ultraviolet shielding composites: A comprehensive review. International Journal of Biological Macromolecules 2024, 280 , 135477. https://doi.org/10.1016/j.ijbiomac.2024.135477
  5. Sweety Kalita, Amar K. Mohanty, Manjusri Misra, Avik Mukherjee, Santosh Kumar. Introduction to Active Food Packaging System. 2024, 1-37. https://doi.org/10.1002/9781394189595.ch1
  6. Muhammad Zubair, Zahid Rauf, Seerat Fatima, Aman Ullah. Lignin-derived bionanocomposites as functional food packaging materials. Sustainable Food Technology 2024, 2 (4) , 945-966. https://doi.org/10.1039/D4FB00105B
  7. Didik Supriyadi, Sabine Bodner, Jozef Keckes, Wolfgang Gindl-Altmutter, Stefan Veigel. Comparing the properties of cellulose nanofibrils from wood and bark of Norway spruce (Picea abies Karst.) and silver poplar (Populus alba L.). Carbohydrate Polymer Technologies and Applications 2024, 7 , 100527. https://doi.org/10.1016/j.carpta.2024.100527
  8. Yanfei Liu, Jingyuan Zhang, Fei Peng, Kui Niu, Wenlong Hou, Bin Du, Yuedong Yang. Development of Chitosan-Based Films Incorporated with Chestnut Flower Essential Oil That Possess Good Anti-Ultraviolet Radiation and Antibacterial Effects for Banana Storage. Coatings 2024, 14 (5) , 548. https://doi.org/10.3390/coatings14050548
  9. Xiya Zhang, Lili Zhang, Yimin Fan, Zhiguo Wang. The case-dependent lignin role in lignocellulose nanofibers preparation and functional application-A review. Green Energy & Environment 2023, 8 (6) , 1553-1566. https://doi.org/10.1016/j.gee.2022.09.008
  10. Yao Xiao, Yu Chen, Zheng-jun Shi, Da-Wei Wang, Jing Yang, Hai-Yan Yang. Lignocellulose Nanofibers Enhanced Mechanical and UV-Blocking Properties of Polyvinyl Alcohol Films. Nano LIFE 2023, 13 (04) https://doi.org/10.1142/S1793984423500101
  11. Kalpani Y. Perera, Amit K. Jaiswal, Swarna Jaiswal. Biopolymer-Based Sustainable Food Packaging Materials: Challenges, Solutions, and Applications. Foods 2023, 12 (12) , 2422. https://doi.org/10.3390/foods12122422
  12. Ana Fernandes, Luísa Cruz-Lopes, Bruno Esteves, Dmitry Evtuguin. Nanotechnology Applied to Cellulosic Materials. Materials 2023, 16 (8) , 3104. https://doi.org/10.3390/ma16083104
  13. Youmei Wang, Huijuan Shao, Hui Pan, Yongze Jiang, Jinqiu Qi, Qi Chen, Shaobo Zhang, Hui Xiao, Yuzhu Chen, Shanshan Jia, Xingyan Huang, Lihua Tu, Zhiping Su, Jiulong Xie. Supramolecular structure of microwave treated bamboo for production of lignin-containing nanocellulose by oxalic acid dihydrate. International Journal of Biological Macromolecules 2023, 230 , 123251. https://doi.org/10.1016/j.ijbiomac.2023.123251
  14. Manuel Peña-Ortiz, Esther Rincón, Luis Serrano, Araceli García. Recent Nanocelullose Applications for Sustainable Agriculture—A Review. 2023, 185-213. https://doi.org/10.1007/978-981-99-2473-8_8
  15. Lu Jin, Jia Xu, Qian Yang, Yujia Huang, Xinjiang Zhang, Wei Yao, Jinshan Wang, Yanteng Zhao, Huafeng Tian, Meng He. Fabrication of cellulose/rectorite composite films for sustainable packaging. International Journal of Biological Macromolecules 2023, 224 , 1471-1477. https://doi.org/10.1016/j.ijbiomac.2022.10.234
  16. Paul Baker, Adam Charlton, Chris Johnston, James J. Leahy, Kevin Lindegaard, Italo Pisano, John Prendergast, Dave Preskett, Campbell Skinner. A review of Willow (Salix spp.) as an integrated biorefinery feedstock. Industrial Crops and Products 2022, 189 , 115823. https://doi.org/10.1016/j.indcrop.2022.115823
  17. Nibedita Dey, Sundaram Vickram, Sundaram Thanigaivel, Ramasamy Subbaiya, Woong Kim, Natchimuthu Karmegam, Muthusamy Govarthanan. Nanomaterials for transforming barrier properties of lignocellulosic biomass towards potential applications – A review. Fuel 2022, 316 , 123444. https://doi.org/10.1016/j.fuel.2022.123444
  18. Yujie Li, Yifan Chen, Qiang Wu, Jingda Huang, Yadong Zhao, Qian Li, Siqun Wang. Improved Hydrophobic, UV Barrier and Antibacterial Properties of Multifunctional PVA Nanocomposite Films Reinforced with Modified Lignin Contained Cellulose Nanofibers. Polymers 2022, 14 (9) , 1705. https://doi.org/10.3390/polym14091705
  19. Meng He, Tong Lu, Zhengtao Jia, Huafeng Tian, Mengna Feng, Xinjiang Zhang, Meng Zhang, Chengshuang Wang, Yanteng Zhao, Jun Qiu. Fabrication and properties of novel chitosan/ZnO composite bioplastic. Cellulose 2022, 29 (1) , 233-243. https://doi.org/10.1007/s10570-021-04315-6
  20. Kun Liu, Haishun Du, Ting Zheng, Wei Liu, Meng Zhang, Huayu Liu, Xinyu Zhang, Chuanling Si. Lignin-containing cellulose nanomaterials: preparation and applications. Green Chemistry 2021, 23 (24) , 9723-9746. https://doi.org/10.1039/D1GC02841C
  21. Jinze Dou, Vijaya Chandgude, Tapani Vuorinen, Sandip Bankar, Sami Hietala, Huy Quang Lê. Enhancing Biobutanol Production from biomass willow by pre-removal of water extracts or bark. Journal of Cleaner Production 2021, 327 , 129432. https://doi.org/10.1016/j.jclepro.2021.129432
  22. Yi Zhang, Abu Naser Md Ahsanul Haque, Maryam Naebe. Lignin–Cellulose Nanocrystals from Hemp Hurd as Light-Coloured Ultraviolet (UV) Functional Filler for Enhanced Performance of Polyvinyl Alcohol Nanocomposite Films. Nanomaterials 2021, 11 (12) , 3425. https://doi.org/10.3390/nano11123425
Download PDF
Go to ACS Applied Nano Materials
Get e-Alerts
Get e-Alerts

ACS Applied Nano Materials

Cite this: ACS Appl. Nano Mater. 2021, 4, 3, 2921–2929
Click to copy citationCitation copied!
https://doi.org/10.1021/acsanm.1c00071
Published February 26, 2021

Copyright © 2021 American Chemical Society. This publication is licensed under

CC-BY 4.0 .

Article Views

2821

Altmetric

-

Citations

22
Learn about these metrics

Article Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.

Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.

The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated.

  • Abstract

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 1

    Figure 1. Experimental flow of fabricating lignin-containing cellulose nanofibrils (LCNF) and LCNF films from hot water-extracted willow bark (HWEWB), using a recyclable acid hydrotrope (p-TsOH).

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 2

    Figure 2. Solid-state 13C CP/MAS spectra of (a) the willow bark; (b) LCNF from WB; and (c) dissolved HMW fraction after treating WB with aqueous 60% p-TsOH. Abbreviations: see caption to Table 1. Label numbers: see caption to Table S3.

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 3

    Figure 3. SEM images of freeze-dried LCNFs prepared from p-TsOH-treated willow bark (WB) and hot water-extracted willow bark (HWEWB) under 6 and 12 cycles of microfluidization: (a) WB 6; (b) WB 12; (c) HWEWB 6; and (d) HWEWB 12.

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 4

    Figure 4. SEM images of the LCNF films of p-TsOH-treated willow bark (WB) and hot water-extracted willow bark (HWEWB) after 6 and 12 cycles of microfluidization in comparison with the MFC film of softwood kraft pulp and willow wood LCNF film: (18) (a) WB 6; (b) WB 12; (c) MFC (softwood kraft pulp); (d) HWEWB 6; (e) HWEWB 12; and (f) willow wood after fractionation with 60% p-TsOH.

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 5

    Figure 5. UV–vis transmission spectra of LCNF films produced from willow bark (WB) and hot water-extracted willow bark (HWEWB) in comparison with an MFC film of bleached kraft pulp in the wavelength range of 290–400 nm.

    High Resolution Image
    Download MS PowerPoint Slide

  • References

    This article references 47 other publications.

    1. 1
      Rutten, M. M. What economic theory tells us about the impacts of reducing food losses and/or waste: implications for research, policy and practice. Agric. Food Secur. 2013, 2, 1– 13,  DOI: 10.1186/2048-7010-2-13
      There is no corresponding record for this reference.
    2. 2
      Wang, J.; Gardner, D. J.; Stark, N. M.; Bousfield, D. W.; Tajvidi, M.; Cai, Z. Moisture and Oxygen Barrier Properties of Cellulose Nanomaterial-Based Films. ACS Sustainable Chem. Eng. 2018, 6, 49– 70,  DOI: 10.1021/acssuschemeng.7b03523
      2
      Moisture and Oxygen Barrier Properties of Cellulose Nanomaterial-Based Films
      Wang, Jinwu; Gardner, Douglas J.; Stark, Nicole M.; Bousfield, Douglas W.; Tajvidi, Mehdi; Cai, Zhiyong
      ACS Sustainable Chemistry & Engineering (2018), 6 (1), 49-70CODEN: ASCECG; ISSN:2168-0485. (American Chemical Society)
      A review. Applications of cellulose nanomaterials (CNMs) have attracted increasing attention in recent years. One conceivable path lies in their com. applications for packaging, in which their barrier properties will play an important role in detg. their competiveness with conventional materials. This review critically analyzes the performance of CNMs acting as a barrier against moisture and oxygen permeation in CNM films, CNM coated polymers and papers, and CNM reinforced polymer composites, gives some insights into remaining challenges, and brings an overall perspective of compositing CNMs with other materials to achieve balanced properties adequate for barrier packaging. In general, CNMs are a poor moisture barrier but excellent oxygen barrier in the dry state and are still good below 65% relative humidity. The addn. of CNMs can improve oxygen barrier of the resulting polymer composites; however, Neat CNM coatings and films can afford better oxygen barrier properties than dispersed CNMs in coatings and nanocomposites. The morphol. and surface functionality of CNMs can be tailored to maximize the barrier performance of materials comprising them. The higher the surface charge d. of CNMs, the better the barrier performance of coated polymers. Like other oxygen barriers such as ethylene vinyl alc. and cellophane, the moisture sensitivity and sealability of CNMs can be improved by sandwiching them with high moisture resistant and sealable polymers such as a polyolefin. A multilayered structure with layers of CNMs providing oxygen resistance covered by other layers of polymers providing moisture resistance and sealability might be competitive in barrier packaging markets dominated by synthetic plastics.
    3. 3
      Choe, E.; Min, D. B. Chemistry and Reactions of Reactive Oxygen Species in Foods. Crit. Rev. Food Sci. Nutr. 2006, 46, 1– 22,  DOI: 10.1080/10408390500455474
      3
      Chemistry and reactions of reactive oxygen species in foods
      Choe, Eunok; Min, David B.
      Critical Reviews in Food Science and Nutrition (2006), 46 (1), 1-22CODEN: CRFND6; ISSN:1040-8398. (Taylor & Francis, Inc.)
      A review. Reactive oxygen species (ROS) are formed enzymically, chem., photochem., and by irradn. of food. They are also formed by the decompn. and the inter-reactions of ROS. Hydroxy radical is the most reactive ROS, followed by singlet oxygen. Reactions of ROS with food components produce undesirable volatile compds. and carcinogens, destroy essential nutrients, and change the functionalities of proteins, lipids, and carbohydrates. Lipid oxidn. by ROS produces low mol. volatile aldehydes, alcs., and hydrocarbons. ROS causes crosslink or cleavage of proteins and produces low mol. carbonyls from carbohydrates. Vitamins are easily oxidized by ROS, esp. singlet oxygen. The singlet oxygen reaction rate was the highest in ss-carotene, followed by tocopherol, riboflavin, vitamin D, and ascorbic acid.
    4. 4
      Kwon, S.; Orsuwan, A.; Bumbudsanpharoke, N.; Yoon, C.; Choi, J.; Ko, S. A Short Review of Light Barrier Materials for Food and Beverage Packaging. Korean J. Packag. Sci. Technol. 2018, 24, 141– 148,  DOI: 10.20909/kopast.2018.24.3.141
      There is no corresponding record for this reference.
    5. 5
      Cardoso, D. R.; Libardi, S. H.; Skibsted, L. H. Riboflavin as a Photosensitizer. Effects on human Health and Food Quality. Food Funct. 2012, 3, 487– 502,  DOI: 10.1039/c2fo10246c
      5
      Riboflavin as a photosensitizer. Effects on human health and food quality
      Cardoso, Daniel R.; Libardi, Silvia H.; Skibsted, Leif H.
      Food & Function (2012), 3 (5), 487-502CODEN: FFOUAI; ISSN:2042-6496. (Royal Society of Chemistry)
      A review. Riboflavin, vitamin B2, and flavins (as riboflavin building blocks or degrdn. products) are efficient photosensitizers inducing oxidative damage to light-exposed tissue and food by substrate-dependent mechanisms, for which protection is offered by specific nutrients. Phenolic and N-heterocyclic amino acids and their peptides and proteins deactivate triplet-excited state riboflavin in diffusion controlled processes, efficiently competing with deactivation by oxygen, resulting in direct (so called Type I) protein degrdn. through electron transfer or proton-coupled electron transfer. In light-exposed tissue, such often long lived protein radicals may as primary photoproducts initiate lipid and vitamin oxidn. In contrast, for lipid systems, oxygen deactivation of triplet-excited state riboflavin, resulting in formation of singlet oxygen, is under aerobic conditions faster than direct deactivation by lipids, which otherwise under anaerobic conditions occurs as hydrogen atom transfer from polyunsatd. lipids to triplet riboflavin. Singlet oxygen adds to unsatd. lipids and forms lipid hydroperoxides as primary lipid oxidn. products or oxidizes proteins (Type II mechanism). Carotenoids seem not to deactivate triplet riboflavin, while chromanols like vitamin E and plant polyphenols are efficient in such deactivation yielding protection of proteins and lipids by these phenols. Indirect protection against the triplet reactivity of riboflavin is further important for polyphenols as riboflavin singlet excited state quenchers in effectively preventing riboflavin intersystem crossing to yield the reactive triplet state. Riboflavin photosensitization becomes crit. for degrdn. of proteins, unsatd. lipids, and folate, thiamine, ascorbate and other vitamins during light exposure of food during storage. For skin, eye and other tissue exposed to high intensity light, dietary polyphenols like flavonoids are important in direct protection against photosensitized oxidn., while dietary carotenoids may yield protection through inner-filter effects, through scavenging of radicals resulting from Type I photosensitization, and through quenching of singlet oxygen formed in Type II photosensitization. Both carotenoids and polyphenols accordingly counteract the degenerative effect induced by riboflavin exposed to light, although by different mechanisms.
    6. 6
      Majdi, M.; Milani, B. Y.; Movahedan, A.; Wasielewski, L.; Djalilian, A. R. The Role of Ultraviolet Radiation in the Ocular System of Mammals. Photonics 2014, 1, 347– 368,  DOI: 10.3390/photonics1040347
      There is no corresponding record for this reference.
    7. 7
      Ferrer, A.; Pal, L.; Hubbe, M. Nanocellulose in packaging: Advances in barrier layer technologies. Ind. Crops Prod. 2017, 95, 574– 582,  DOI: 10.1016/j.indcrop.2016.11.012
      7
      Nanocellulose in packaging: Advances in barrier layer technologies
      Ferrer, Ana; Pal, Lokendra; Hubbe, Martin
      Industrial Crops and Products (2017), 95 (), 574-582CODEN: ICRDEW; ISSN:0926-6690. (Elsevier B.V.)
      The review aims at reporting on recent developments in nanocellulose-based materials and their applications in packaging with special focus on oxygen and water vapor barrier characteristics. Nanocellulose materials, including cellulose nanocrystals (CNC), nanofibrillated cellulose (NFC), and bacterial nanocellulose (BNC), have unique properties with the potential to dramatically impact many com. markets including packaging. In addn. to being derived from a renewable resource that is both biodegradable and non-toxic, nanocellulose exhibits extremely high surface area and crystallinity and has tunable surface chem. These features give nanocellulose materials great potential to sustainably enhance oxygen and water vapor barrier properties when used as coating, fillers in composites and as self-standing thin films.
    8. 8
      Jiang, Y.; Song, Y.; Miao, M.; Cao, S.; Feng, X.; Fang, J.; Shi, L. Transparent nanocellulose hybrid films functionalized with ZnO nanostructures for UV-blocking. J. Mater. Chem. C 2015, 3, 6717– 6724,  DOI: 10.1039/C5TC00812C
      8
      Transparent nanocellulose hybrid films functionalized with ZnO nanostructures for UV-blocking
      Jiang, Yaoquan; Song, Yuanyuan; Miao, Miao; Cao, Shaomei; Feng, Xin; Fang, Jianhui; Shi, Liyi
      Journal of Materials Chemistry C: Materials for Optical and Electronic Devices (2015), 3 (26), 6717-6724CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)
      Transparent, nanocellulose-ZnO (NC-ZnO) hybrid films were fabricated via a pressure controlled extrusion process using NC fibrils and sheet-like ZnO (s-ZnO) or belt-like ZnO (b-ZnO) nanostructures. The s-ZnO and b-ZnO conjoined with the NC fibrils to form a heterogeneous, fibrous network structure. The NC-ZnO hybrid films with different amts. of ZnO nanostructures showed a synergic feature of high optical transparency and excellent UV-blocking. The results indicated that NC assembled with s-ZnO hybrid film possessed excellent UV-blocking ability in a wide range from 200 to 375 nm, in contrast to NC-b-ZnO. Moreover, the prominent thermal and photo stability of transparent NC-ZnO hybrid films enhanced extensibility and ease of use for diverse biol. applications, which require tolerance of temp. changes.
    9. 9
      Nouri, L.; Nafchi, A. M. Antibacterial, mechanical, and barrier properties of sago starch film incorporated with betel leaves extract. Int. J. Biol. Macromol. 2014, 66, 254– 259,  DOI: 10.1016/j.ijbiomac.2014.02.044
      9
      Antibacterial, mechanical, and barrier properties of sago starch film incorporated with betel leaves extract
      Nouri, Leila; Mohammadi Nafchi, Abdorreza
      International Journal of Biological Macromolecules (2014), 66 (), 254-259CODEN: IJBMDR; ISSN:0141-8130. (Elsevier B.V.)
      The antimicrobial, mech. and barrier properties and light transmission of sago starch film incorporated with different percentage of Betel leaf ext. (5%, 10%, 20%, and 30%) were evaluated. With regard to mech. properties, tensile strength decreased when the percentage of ext. increased. Elongation at break (%) and seal strength (N/m) increased with increasing percentage of ext. from 5% to 20%, while decreased for films contg. 30% ext. due to heterogeneity of films in this percentage. With regard to barrier properties, water vapor and oxygen barrier properties decreased in all samples when percentage of the ext. increased. Antimicrobial activity of all the films increased against both Gram pos. and Gram neg. bacteria as percentage of Betel leaf ext. increased, except for Psuedomonas aeruginosa, which was not susceptible at any percentage of the ext.
    10. 10
      Begley, T. H.; Biles, J. E.; Cunningham, C.; Piringer, O. Migration of a UV stabilizer from polyethylene terephthalate (PET) into food simulants. Food Addit. Contam. 2004, 21, 1007– 1014,  DOI: 10.1080/02652030400010447
      10
      Migration of a UV stabilizer from polyethylene terephthalate (PET) into food simulants
      Begley, T. H.; Biles, J. E.; Cunningham, C.; Piringer, O.
      Food Additives & Contaminants (2004), 21 (10), 1007-1014CODEN: FACOEB; ISSN:0265-203X. (Taylor & Francis Ltd.)
      The migration characteristics of the UV stabilizer Tinuvin 234 (2-(2H-benzotriazol-2-yl)-4,6-bis (1-methyl-1-phenylethyl)phenol) into food simulants has been measured from polyethylene terephthalate (PET) using HPLC with UV detection. Ethanol/water, isooctane and a fractionated coconut oil simulant (Miglyol) were used as food simulating solvents. The migration characteristics were measured at temps. in the range of 40-70°. Diffusion coeffs. were detd. to be in the range of 1×10-14 cm2 s-1 to 1×10-18 cm2 s-1. At 40°, the amt. of migration into 95% ethanol after 10 days was 2 μg dm-2. Isooctane is detd. to be a good fatty food simulant that provides similar results for PET to those of fatty foods.
    11. 11
      Skocaj, M.; Filipic, M.; Petkovic, J.; Novak, S. Titanium dioxide in our everyday life; is it safe?. Radiol. Oncol. 2011, 45, 227– 247,  DOI: 10.2478/v10019-011-0037-0
      11
      Titanium dioxide in our everyday life; is it safe?
      Skocaj, Matej; Filipic, Metka; Petkovic, Jana; Novak, Sasa
      Radiology and Oncology (2011), 45 (4), 227-247CODEN: RONCEM; ISSN:1318-2099. (Association of Radiology and Oncology)
      A review. Background. Titanium dioxide (TiO2) is considered as an inert and safe material and has been used in many applications for decades. However, with the development of nanotechnologies TiO2 nanoparticles, with numerous novel and useful properties, are increasingly manufd. and used. Therefore increased human and environmental exposure can be expected, which has put TiO2 nanoparticles under toxicol. scrutiny. Mechanistic toxicol. studies show that TiO2 nanoparticles predominantly cause adverse effects via induction of oxidative stress resulting in cell damage, genotoxicity, inflammation, immune response etc. The extent and type of damage strongly depends on phys. and chem. characteristics of TiO2 nanoparticles, which govern their bioavailability and reactivity. Based on the exptl. evidence from animal inhalation studies TiO2 nanoparticles are classified as "possible carcinogenic to humans" by the International Agency for Research on Cancer and as occupational carcinogen by the National Institute for Occupational Safety and Health. The studies on dermal exposure to TiO2 nanoparticles, which is in humans substantial through the use of sunscreens, generally indicate negligible transdermal penetration; however data are needed on long-term exposure and potential adverse effects of photo-oxidn. products. Although TiO2 is permitted as an additive (E171) in food and pharmaceutical products we do not have reliable data on its absorption, distribution, excretion and toxicity on oral exposure. TiO2 may also enter environment, and while it exerts low acute toxicity to aquatic organisms, upon long-term exposure it induces a range of sub-lethal effects. Conclusions. Until relevant toxicol. and human exposure data that would enable reliable risk assessment are obtained, TiO2 nanoparticles should be used with great care.
    12. 12
      Yousif, E.; Haddad, R. Photodegradation and photostabilization of polymers, especially polystyrene: review. SpringerPlus 2013, 2, 398  DOI: 10.1186/2193-1801-2-398
      12
      Photodegradation and photostabilization of polymers, especially polystyrene: review
      Yousif Emad; Haddad Raghad
      SpringerPlus (2013), 2 (), 398 ISSN:2193-1801.
      Exposure to ultraviolet (UV) radiation may cause the significant degradation of many materials. UV radiation causes photooxidative degradation which results in breaking of the polymer chains, produces free radical and reduces the molecular weight, causing deterioration of mechanical properties and leading to useless materials, after an unpredictable time. Polystyrene (PS), one of the most important material in the modern plastic industry, has been used all over the world, due to its excellent physical properties and low-cost. When polystyrene is subjected to UV irradiation in the presence of air, it undergoes a rapid yellowing and a gradual embrittlement. The mechanism of PS photolysis in the solid state (film) depends on the mobility of free radicals in the polymer matrix and their bimolecular recombination. Free hydrogen radicals diffuse very easily through the polymer matrix and combine in pairs or abstract hydrogen atoms from polymer molecule. Phenyl radical has limited mobility. They may abstract hydrogen from the near surrounding or combine with a polymer radical or with hydrogen radicals. Almost all synthetic polymers require stabilization against adverse environmental effects. It is necessary to find a means to reduce or prevent damage induced by environmental components such as heat, light or oxygen. The photostabilization of polymers may be achieved in many ways. The following stabilizing systems have been developed, which depend on the action of stabilizer: (1) light screeners, (2) UV absorbers, (3) excited-state quenchers, (4) peroxide decomposers, and (5) free radical scavengers; of these, it is generally believed that excited-state quenchers, peroxide decomposers, and free radical scavengers are the most effective. Research into degradation and ageing of polymers is extremely intensive and new materials are being synthesized with a pre-programmed lifetime. New stabilizers are becoming commercially available although their modes of action are sometimes not thoroughly elucidated. They target the many possible ways of polymer degradation: thermolysis, thermooxidation, photolysis, photooxidation, radiolysis etc. With the goal to increase lifetime of a particular polymeric material, two aspects of degradation are of particular importance: Storage conditions, and Addition of appropriate stabilizers. A profound knowledge of degradation mechanisms is needed to achieve the goal.
    13. 13
      Isogai, A.; Saito, T.; Fukuzumi, H. TEMPO-oxidized cellulose nanofibers. Nanoscale 2011, 3, 71– 85,  DOI: 10.1039/C0NR00583E
      13
      TEMPO-oxidized cellulose nanofibers
      Isogai, Akira; Saito, Tsuguyuki; Fukuzumi, Hayaka
      Nanoscale (2011), 3 (1), 71-85CODEN: NANOHL; ISSN:2040-3372. (Royal Society of Chemistry)
      A review on prepn. methods and fundamental characteristics of TEMPO-oxidized cellulose nanofibers (TOCN) and tensile strengths, thermal stability, and oxygen permeability of TOCN/poly(lactic acid) composite.
    14. 14
      Sirviö, J. A.; Kolehmainen, A.; Visanko, M.; Liimatainen, H.; Niinimäki, J.; Hormi, O. E. O. Strong, Self-Standing Oxygen Barrier Films from Nanocelluloses Modified with Regioselective Oxidative Treatments. ACS Appl. Mater. Interfaces 2014, 6, 14384– 14390,  DOI: 10.1021/am503659j
      14
      Strong, Self-Standing Oxygen Barrier Films from Nanocelluloses Modified with Regioselective Oxidative Treatments
      Sirvio, Juho Antti; Kolehmainen, Aleksi; Visanko, Miikka; Liimatainen, Henrikki; Niinimaki, Jouko; Hormi, Osmo E. O.
      ACS Applied Materials & Interfaces (2014), 6 (16), 14384-14390CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
      In this work, three self-standing nanocellulose films were produced from birch pulp using regioselective oxidn. and further derivatization treatments. The modified celluloses were synthesized using periodate oxidn., followed by chlorite oxidn., bisulfite addn., or reductive amination with amino acid taurine, which resulted in dicarboxylic acid cellulose (DCC), α-hydroxy sulfonic acid cellulose (HSAC), and taurine-modified cellulose (TC), resp. The nanocelluloses were fabricated by mech. disintegration using high-pressure homogenization. Mech. and barrier properties of the nanocellulose films were characterized. Two (2,2,6,6-tetramethyl-piperidin-1-yl)oxyl (TEMPO) oxidn.-based nanocellulose films were also produced, and their properties were compared to the periodate-based nanocellulose films. All of the periodate-based nanocellulose films showed high tensile strength (130-163 MPa) and modulus (19-22 GPa). Oxygen barrier properties of the films were superior to many synthetic and composite materials; in particular, the nanofibrillated DCC films had oxygen permeability as low as 0.12 cm3 μm/(m2 d kPa) at 50% relative humidity. Compared to films of TEMPO-oxidized nanocelluloses, all of the periodate-based nanocellulose films had similar or even better mech. and barrier properties, demonstrating versatility of periodate oxidn. to obtain nanocellulose films with adjustable properties. Also, for the first time, amino-acid-based cellulose modification was used in the prodn. of nanocellulose.
    15. 15
      Visanko, M.; Liimatainen, H.; Sirviö, J. A.; Mikkonen, K. S.; Tenkanen, M.; Sliz, R.; Hormi, O.; Niinimäki, J. Butylamino-functionalized cellulose nanocrystal films: barrier properties and mechanical strength. RSC Adv. 2015, 5, 15140– 15146,  DOI: 10.1039/C4RA15445B
      15
      Butylamino-functionalized cellulose nanocrystal films: barrier properties and mechanical strength
      Visanko, Miikka; Liimatainen, Henrikki; Sirvio, Juho Antti; Mikkonen, Kirsi S.; Tenkanen, Maija; Sliz, Rafal; Hormi, Osmo; Niinimaki, Jouko
      RSC Advances (2015), 5 (20), 15140-15146CODEN: RSCACL; ISSN:2046-2069. (Royal Society of Chemistry)
      Cellulose nanocrystals (CNCs), which are strong, rod-like constituents of plant cellulose, are promising materials for green packaging applications as the material is capable of forming tortuous network structures with efficient barriers against outside gases. Here, a two-step procedure based on periodate oxidn. followed by reductive amination was used as a pretreatment to modify bleached birch chem. wood pulp. Individualized CNCs were obtained from three different butylamino-functionalized pulps by mech. homogenization. The fabricated CNCs were utilized to form transparent barrier films with a vacuum filtration method. All the butylamino-functionalized CNC films showed capability to resist oxygen permeability even at high relative humidity (RH 80%), and values as low as 5.9 ± 0.2 cm3 μm/m2/day/kPa were recorded for pure cellulose based film using tert-butylamino-functionalized CNCs. In addn. a barriers against water vapor permeation and dynamic vapor sorption were detd. up to relative humidities of 80 and 90%, resp. For surface characterization of the films time-dependent contact angles and surface roughness were measured. The films had good mech. characteristics with tensile strength of 105.7 ± 9.7 MPa, strain-to-failure of 6.4 ± 0.6% and a Young's modulus of 5.8 ± 0.8 GPa.
    16. 16
      Missoum, K.; Belgacem, M. N.; Bras, J. Nanofibrillated Cellulose Surface Modification: A Review. Materials 2013, 6, 1745– 1766,  DOI: 10.3390/ma6051745
      16
      Nanofibrillated Cellulose Surface Modification: A Review
      Missoum Karim; Belgacem Mohamed Naceur; Bras Julien
      Materials (Basel, Switzerland) (2013), 6 (5), 1745-1766 ISSN:1996-1944.
      Interest in nanofibrillated cellulose (NFC) has increased notably over recent decades. This bio-based nanomaterial has been used essentially in bionanocomposites or in paper thanks to its high mechanical reinforcement ability or barrier property respectively. Its nano-scale dimensions and its capacity to form a strong entangled nanoporous network have encouraged the emergence of new high-value applications. It is worth noting that chemical surface modification of this material can be a key factor to achieve a better compatibility with matrices. In order to increase the compatibility in different matrices or to add new functions, surface chemical modification of NFC appears to be the prior choice to conserve its intrinsic nanofibre properties. In this review, the authors have proposed for the first time an overview of all chemical grafting strategies used to date on nanofibrillated cellulose with focus on surface modification such as physical adsorption, molecular grafting or polymer grafting.
    17. 17
      Adudonia, K. S.; Saad, G. R.; Naguib, H. F.; Ewis, M.; Zahran, D.; Elsabee, M. Z. Surface modification of polypropylene film by grafting with vinyl monomers for the attachment of chitosan. J. Polym. Res. 2018, 25, 125,  DOI: 10.1007/s10965-018-1517-3
      There is no corresponding record for this reference.
    18. 18
      Dou, J.; Bian, H.; Yelle, D. J.; Ago, M.; Vajanto, K.; Vuorinen, T.; Zhu, J. Y. Lignin containing cellulose nanofibril production from willow bark at 80 °C using a highly recyclable acid hydrotrope. Ind. Crops Prod. 2019, 129, 15– 23,  DOI: 10.1016/j.indcrop.2018.11.033
      18
      Lignin containing cellulose nanofibril production from willow bark at 80 °C using a highly recyclable acid hydrotrope
      Dou, Jinze; Bian, Huiyang; Yelle, Daniel J.; Ago, Mariko; Vajanto, Krista; Vuorinen, Tapani; Zhu, Junyong
      Industrial Crops and Products (2019), 129 (), 15-23CODEN: ICRDEW; ISSN:0926-6690. (Elsevier B.V.)
      We conducted the first comparative exploration on lignin contg. cellulose nanofibril films prepd. alternatively from willow bark and wood using a highly recyclable acid hydrotrope, aq. p-toluenesulfonic acid, as a sustainable means for isolating the nanofibrils. The nanofibrils of willow bark were hydrophobic and produced dense films of high strength under hot pressing. The hydrophobicity resulted from condensation of the residual lignin with low mol. wt. arom. substances of the bark and hydroxymethylfurfural formed in situ from fructose that is also present in the bark.
    19. 19
      Chen, L.; Dou, J.; Ma, Q.; Li, N.; Wu, R.; Bian, H.; Yelle, D. J.; Vuorinen, T.; Fu, S.; Pan, X.; Zhu, J. Rapid and near-complete dissolution of wood lignin at ≤80 °C by a recyclable acid hydrotrope. Sci. Adv. 2017, 3, e1701735  DOI: 10.1126/sciadv.1603079
      19
      Rapid and near-complete dissolution of wood lignin at ≤80°C by a recyclable acid hydrotrope
      Chen, Liheng; Dou, Jinze; Ma, Qianli; Li, Ning; Wu, Ruchun; Bian, Huiyang; Yelle, Daniel J.; Vuorinen, Tapani; Fu, Shiyu; Pan, Xuejun; Zhu, Junyong
      Science Advances (2017), 3 (9), e1701735/1-e1701735/11CODEN: SACDAF; ISSN:2375-2548. (American Association for the Advancement of Science)
      Wereport the discovery of the hydrotropic properties of a recyclable arom. acid, p-toluenesulfonic acid (p-TsOH), for potentially low-cost and efficient fractionation of wood through rapid and near-complete dissoln. of lignin. Approx. 90% of poplar wood (NE222) lignin can be dissolved at 80°C in 20 min. Equivalent delignification using known hydrotropes, such as arom. salts, can be achieved only at 150°C or higher for more than 10 h or at 150°C for 2 h with alk. pulping. p-TsOH fractionated wood into two fractions: (i) a primarily celluloserich water-insol. solid fraction that can be used for the prodn. of high-value building blocks, such as dissolving pulp fibers, lignocellulosic nanomaterials, and/or sugars through subsequent enzymic hydrolysis; and (ii) a spent acid liquor stream contg. mainly dissolved lignin that can be easily pptd. as lignin nanoparticles by dilg. the spent acid liquor to below the minimal hydrotrope concn. Our NMR analyses of the dissolved lignin revealed that p-TsOH can depolymerize lignin via ether bond cleavage and can sep. carbohydrate-free lignin from the wood. p-TsOH has a relatively low water soly., which can facilitate efficient recovery using com. proven crystn. technol. by cooling the concd. spent acid soln. to ambient temps. to achieve environmental sustainability through recycling of p-TsOH.
    20. 20
      Rajala, S.; Siponkoski, T.; Sarlin, E.; Mettänen, M.; Vuoriluoto, M.; Pammo, A.; Juuti, J.; Rojas, O. J.; Franssila, S.; Tuukkanen, S. Cellulose Nanofibril Film as a Piezoelectric Sensor Material. ACS Appl. Mater. Interfaces 2016, 8, 15607– 15614,  DOI: 10.1021/acsami.6b03597
      20
      Cellulose Nanofibril Film as a Piezoelectric Sensor Material
      Rajala, Satu; Siponkoski, Tuomo; Sarlin, Essi; Mettanen, Marja; Vuoriluoto, Maija; Pammo, Arno; Juuti, Jari; Rojas, Orlando J.; Franssila, Sami; Tuukkanen, Sampo
      ACS Applied Materials & Interfaces (2016), 8 (24), 15607-15614CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
      Self-standing films (45 μm thick) of native cellulose nanofibrils (CNFs) were synthesized and characterized for their piezoelec. response. The surface and the microstructure of the films were evaluated with image-based anal. and SEM. The measured dielec. properties of the films at 1 kHz and 9.97 GHz indicated a relative permittivity of 3.47 and 3.38 and loss tangent tan δ of 0.011 and 0.071, resp. The films were used as functional sensing layers in piezoelec. sensors with corresponding sensitivities of 4.7-6.4 pC/N in ambient conditions. This piezoelec. response is expected to increase remarkably upon film polarization resulting from the alignment of the cellulose cryst. regions in the film. The CNF sensor characteristics were compared with those of polyvinylidene fluoride (PVDF) as ref. piezoelec. polymer. Overall, the results suggest that CNF is a suitable precursor material for disposable piezoelec. sensors, actuators, or energy generators with potential applications in the fields of electronics, sensors, and biomedical diagnostics.
    21. 21
      Mendes, J. A. S.; Prozil, S. O.; Evtuguin, D. V.; Lopes, L. P. C. Towards comprehensive utilization of winemaking residues: Characterization of grape skins from red grape pomaces of variety Touriga Nacional. Ind. Crops Prod. 2013, 43, 25– 32,  DOI: 10.1016/j.indcrop.2012.06.047
      21
      Towards comprehensive utilization of winemaking residues: Characterization of grape skins from red grape pomaces of variety Touriga Nacional
      Mendes, Joana A. S.; Prozil, Sonia O.; Evtuguin, Dmitry V.; Lopes, Luisa P. Cruz
      Industrial Crops and Products (2013), 43 (), 25-32CODEN: ICRDEW; ISSN:0926-6690. (Elsevier B.V.)
      The chem. compn. and the structural features of macromol. components from red grape skins (variety Touriga Nacional) have been evaluated. The results of chem. analyses revealed the following contents of the main constituents: cellulose (20.8%), hemicelluloses (12.5%), proteins (18.8%), tannins (13.8%), extractives sol. in dichloromethane (5.0%) and ash (7.8%). Cellulose of grape skins is typical cellulose I polymorph with a degree of crystallinity of 66.1% as assessed by X-ray scattering. The hemicelluloses were analyzed by neutral sugars anal., methylation anal. and 1D/2D 1H NMR. The water-sol. compds. (26.4%) are composed mainly of monomeric sugars (glucose and fructose) and a complex mixt. of hemicelluloses, the most abundant being pectin and acetylated glucomannan. The major part of structural polysaccharides (cellulose, xylan, xyloglucan, etc.) is embedded in cuticular layer and is poorly accessible to the acid hydrolysis. The cuticular substances contributed to ca. 8.5% of grape skins and their chem. structure has been evaluated by methanolysis. The possibility of comprehensive utilization of grape skins has been discussed.
    22. 22
      Webb, H. K.; Truong, V. K.; Hasan, J.; Fluke, C.; Crawford, R. J.; Ivanova, E. P. Roughness Parameters for Standard Description of Surface Nanoarchitecture. Scanning 2012, 34, 257– 263,  DOI: 10.1002/sca.21002
      22
      Roughness Parameters for Standard Description of Surface Nanoarchitecture
      Webb, Hayden K.; Truong, Vi Khanh; Hasan, Jafar; Fluke, Christopher; Crawford, Russell J.; Ivanova, Elena P.
      Scanning (2012), 34 (4), 257-263CODEN: SCNNDF; ISSN:0161-0457. (John Wiley & Sons, Inc.)
      The nanoarchitecture and surface roughness of metallic thin films prepd. by magnetron sputtering were analyzed to det. the topog. statistics that give the optimum description of their nanoarchitechture. Nanoscale topog. profiles were generated by performing at. force microscopy (AFM) scans of 1 μm × 1 μm areas of titanium and silver films of three different thicknesses (3 nm, 12 nm, and 150 nm). Of the titanium films, the 150-nm film had the highest av. roughness (Ra = 2.63 nm), more than four times that of the 3-nm and 12-nm titanium films. When silver films were coated on top of 150-nm titanium films, the av. roughness increased further; the 3-nm (Ra = 4.96 nm) and 150-nm (Ra = 4.65 nm) silver films av. roughnesses were approx. twice that of the 150-nm titanium film. For topog. anal., seven statistical parameters were calcd. These parameters included commonly used roughness measurements, as well as some less commonly used measurements, in order to det. which combination of parameters gave the best overall description of the nanoarchitecture of the films presented. Skewness (Rskw), surface area increase (Rsa), and peak counts (Rpc) provided the best description of horizontal surface dimensions, and in conjunction with vertical descriptors Ra and Rq gave the best characterization of surface architecture. The five roughness parameters Ra, Rq, Rskw, Rsa, and Rpc are proposed as a new std. for describing surface nanoarchitecture. SCANNING 34: 257-263, 2012. © 2012 Wiley Periodicals, Inc.
    23. 23
      Kim, H.; Ralph, J. Solution-state 2D NMR of ball-milled plant cell wall gels in DMSO-d6/pyridine-d5. Org. Biomol. Chem. 2010, 8, 576– 591,  DOI: 10.1039/B916070A
      23
      Solution-state 2D NMR of ball-milled plant cell wall gels in DMSO-d6/pyridine-d5
      Kim, Hoon; Ralph, John
      Organic & Biomolecular Chemistry (2010), 8 (3), 576-591CODEN: OBCRAK; ISSN:1477-0520. (Royal Society of Chemistry)
      NMR fingerprinting of the components of finely divided plant cell walls swelled in DMSO has been recently described. Cell wall gels, produced directly in the NMR tube with perdeutero-dimethylsulfoxide, allowed the acquisition of well resolved/dispersed 2D 13C-1H correlated soln.-state NMR spectra of the entire array of wall polymers, without the need for component fractionation. That is, without actual solubilization, and without apparent structural modification beyond that inflicted by the ball milling and ultrasonication steps, satisfactorily interpretable spectra can be acquired that reveal compositional and structural details regarding the polysaccharide and lignin components in the wall. Here, the profiling method has been improved by using a mixt. of perdeuterated DMSO and pyridine (4 : 1, vol./vol.). Adding pyridine provided not only easier sample handling because of the better mobility compared to the DMSO-d6-only system but also considerably elevated intensities and improved resoln. of the NMR spectra due to the enhanced swelling of the cell walls. This modification therefore provides a more rapid method for comparative structural evaluation of plant cell walls than is currently available. We examd. loblolly pine (Pinus taeda, a gymnosperm), aspen (Populus tremuloides, an angiosperm), kenaf (Hibiscus cannabinus, an herbaceous plant), and corn (Zea mays L., a grass, i.e., from the Poaceae family). In principle, lignin compn. (notably, the syringyl : guaiacyl : p-hydroxyphenyl ratio) can be quantified without the need for lignin isolation. Correlations for p-coumarate units in the corn sample are readily seen, and a variety of the ferulate correlations are also well resolved; ferulates are important components responsible for cell wall crosslinking in grasses. Polysaccharide anomeric correlations were tentatively assigned for each plant sample based on std. samples and various literature data. With the new potential for chemometric anal. using the 2D NMR fingerprint, this gel-state method may provide the basis for an attractive approach to providing a secondary screen for selecting biomass lines and for optimizing biomass processing and conversion efficiencies.
    24. 24
      Dou, J.; Paltakari, J.; Johansson, L.; Vuorinen, T. Novel Insight into the Separation and Composite Utilization of Sclerenchyma Fiber Bundles of Willow Bark. ACS Sustainable Chem. Eng. 2019, 7, 2964– 2970,  DOI: 10.1021/acssuschemeng.8b04001
      24
      Novel Insight into the Separation and Composite Utilization of Sclerenchyma Fiber Bundles of Willow Bark
      Dou, Jinze; Paltakari, Jouni; Johansson, Leena-Sisko; Vuorinen, Tapani
      ACS Sustainable Chemistry & Engineering (2019), 7 (3), 2964-2970CODEN: ASCECG; ISSN:2168-0485. (American Chemical Society)
      The bark from fast-growing willow crops contains long and strong sclerenchyma fiber bundles, which could potentially replace the pulp and annual plant fibers currently used to reinforce green polymer composites. Here we successfully demonstrate the isolation of fiber bundles of willow bark with a simple alkali treatment under much milder conditions than what pulp fiber sepn. requires. The fiber bundles sepd. had hydrophobic surfaces, which made them compatible with polymers, in this case with polylactic acid, without using any additives. The most hydrophobic fiber bundles of willow bark provided the strongest and toughest composites, superior to the corresponding isotropic composites of pulp and flax fibers. Integration of the fiber bundle isolation with a prior recovery of hot water extractable aroms. from the bark and further processing of the debarked willow stems into bioethanol and lignin, for example, could make the full valorization of the willow biomass feasible.
    25. 25
      Granata, A.; Argyropoulos, D. S. 2-Chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane, a Reagent for the Accurate Determination of the Uncondensed and Condensed Phenolic Moieties in Lignins. J. Agric. Food Chem. 1995, 43, 1538– 1544,  DOI: 10.1021/jf00054a023
      25
      2-Chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane, a Reagent for the Accurate Determination of the Uncondensed and Condensed Phenolic Moieties in Lignins
      Granata, Alessandro; Argyropoulos, Dimitris S.
      Journal of Agricultural and Food Chemistry (1995), 43 (6), 1538-44CODEN: JAFCAU; ISSN:0021-8561. (American Chemical Society)
      The use of 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane as a phosphitylation reagent in quant. 31P NMR anal. of the hydroxyl groups in lignins has been thoroughly examd., and an exptl. protocol recommended for spectra acquisition has been developed. Quant. anal. of six "std. lignins" gave results comparable to those obtained by other methods of anal. Excellent resoln. of the various phenolic hydroxyl environments including those present in condensed moieties was obsd. However, this was at the expense of resoln. in the aliph. hydroxyl region, where no distinction between primary, secondary, and the erythro and threo forms of the secondary hydroxyls of the β-O-4 bonds can be made.
    26. 26
      Sipponen, M. H.; Smyth, M.; Leskinen, T.; Johansson, L.; Österberg, M. All-lignin approach to prepare cationic colloidal lignin particles: stabilization of durable Pickering emulsions. Green Chem. 2017, 19, 5831– 5840,  DOI: 10.1039/C7GC02900D
      26
      All-lignin approach to prepare cationic colloidal lignin particles: stabilization of durable Pickering emulsions
      Sipponen, Mika Henrikki; Smyth, Matthew; Leskinen, Timo; Johansson, Leena-Sisko; Osterberg, Monika
      Green Chemistry (2017), 19 (24), 5831-5840CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
      Surface modification of colloidal lignin particles (CLPs), which are obtained from renewable resources, is a plausible route towards novel biomaterials. Here we show that adsorption of cationic lignin onto spherical CLPs produces pos. charged particles with tailored properties for the stabilization of Pickering emulsions. The threshold dosing of cationic lignin needed to achieve colloidally stable cationic dispersions was 4% relative to the dry wt. of CLPs. Compared to irregular kraft lignin particles or regular CLPs, cationic CLPs stabilized a broader array of durable Pickering emulsions. This all-lignin adsorption process to prep. cationic CLPs is advantageous because it minimizes the consumption of synthetic polymers, and opens new application opportunities for structurally defined nano- and microscale lignin particles.
    27. 27
      Liu, T. Y.; Chang, Y. H. Hydrolysis of proteins with p-Toluenesulfonic acid. Determination of tryptophan. J. Biol. Chem. 1971, 246, 2842– 2848,  DOI: 10.1016/S0021-9258(18)62259-8
      27
      Hydrolysis of proteins with p-toluenesulfonic acid. Determination of tryptophan
      Liu, Teh-Yung; Chang, Yi-Han
      Journal of Biological Chemistry (1971), 246 (9), 2842-8CODEN: JBCHA3; ISSN:0021-9258.
      A new procedure for anals. for tryptophan in proteins and glycoproteins utilizes p-toluenesulfonic acid as the catalyst for hydrolysis and the amino acid analyzer for the quant. estn. of tryptophan. The hydrolysis of proteins is carried out in 3N p-toluenesulfonic acid contg. 0.2% 3-(2-aminoethyl)-indole in evacuated sealed tubes at 110° for 22, 48, or 72 hr. The values of tryptophan obtained were close to the expected integral values and the recoveries of all other amino acids were comparable to those obsd. after hydrolysis with 6N HCl. Since the hydrolyzate can be placed on the ion exchange column without the prior removal of the solvent, which is required when 6N HCl is used for the hydrolysis, the present procedure is more convenient than the use of 6N HCl. This procedure, however, is not designed for the anals. of proteins that are grossly contaminated with carbohydrates, such as feeds. The limit of carbohydrate content that the present procedure can tolerate is 2.0 mg when 2-4 mg of protein are being hydrolyzed with 1.0 ml of the acid.
    28. 28
      Dou, J.; Kim, H.; Li, Y.; Padmakshan, D.; Yue, F.; Ralph, J.; Vuorinen, T. Structural Characterization of Lignins From Willow Bark and Wood. J. Agric. Food Chem. 2018, 66, 7294– 7300,  DOI: 10.1021/acs.jafc.8b02014
      28
      Structural Characterization of Lignins from Willow Bark and Wood
      Dou, Jinze; Kim, Hoon; Li, Yanding; Padmakshan, Dharshana; Yue, Fengxia; Ralph, John; Vuorinen, Tapani
      Journal of Agricultural and Food Chemistry (2018), 66 (28), 7294-7300CODEN: JAFCAU; ISSN:0021-8561. (American Chemical Society)
      Understanding the chem. structure of lignin in willow bark is an indispensable step to design how to sep. its fiber bundles. The whole cell wall and enzyme lignin prepns. sequentially isolated from ball-milled bark, inner bark, and wood were comparatively investigated by NMR spectroscopy and three classical degradative methods, i.e., alk. nitrobenzene oxidn., derivatization followed by reductive cleavage, and anal. thioacidolysis. All results demonstrated that the guaiacyl (G) units were predominant in the willow bark lignin over syringyl (S) and minor p-hydroxyphenyl (H) units. Moreover, the monomer yields and S/G ratio rose progressively from bark to inner bark and wood, indicating that lignin may be more condensed in bark than in other tissues. Addnl., major interunit linkage substructures (β-aryl ethers, phenylcoumarins, and resinols) together with cinnamyl alc. end groups were relatively quantitated by two-dimensional NMR spectroscopy. Bark and inner bark were rich in pectins and proteins, which were present in large quantities and also in the enzyme lignin prepns.
    29. 29
      Kim, H.; Padmakshan, D.; Li, Y.; Rencoret, J.; Hatfield, R. D.; Ralph, J. Characterization and Elimination of Undesirable Protein Residues in Plant Cell Wall Materials for Enhancing Lignin Analysis by Solution-State Nuclear Magnetic Resonance Spectroscopy. Biomacromolecules 2017, 18, 4184– 4195,  DOI: 10.1021/acs.biomac.7b01223
      29
      Characterization and Elimination of Undesirable Protein Residues in Plant Cell Wall Materials for Enhancing Lignin Analysis by Solution-State Nuclear Magnetic Resonance Spectroscopy
      Kim, Hoon; Padmakshan, Dharshana; Li, Yanding; Rencoret, Jorge; Hatfield, Ronald D.; Ralph, John
      Biomacromolecules (2017), 18 (12), 4184-4195CODEN: BOMAF6; ISSN:1525-7797. (American Chemical Society)
      Protein polymers exist in every plant cell wall prepn., and they interfere with lignin characterization and quantification. Here, we report the structural characterization of the residual protein peaks in 2D NMR spectra in corn cob and kenaf samples and note that arom. amino acids are ubiquitous and evident in spectra from various other plants and tissues. The arom. correlations from amino acid residues were identified and assigned as phenylalanine and tyrosine. Phenylalanine's 3/5 correlation peak is superimposed on the peak from typical lignin p-hydroxyphenyl (H-unit) structures, causing an overestimation of the H units. Protein contamination also occurs when using cellulases to prep. enzyme lignins from virtually protein-free wood samples. We used a protease to remove the protein residues from the ball-milled cell walls, and we were able to reveal H-unit structures in lignins more clearly in the 2D NMR spectra, providing a better basis for their estn.
    30. 30
      Dou, J.; Xu, W.; Koivisto, J. J.; Mobley, J. K.; Padmakshan, D.; Kögler, M.; Xu, C.; Willför, S.; Ralph, J.; Vuorinen, T. Characteristics of Hot Water Extracts from the Bark of Cultivated Willow (Salix sp.). ACS Sustainable Chem. Eng. 2018, 6, 5566– 5573,  DOI: 10.1021/acssuschemeng.8b00498
      30
      Characteristics of Hot Water Extracts from the Bark of Cultivated Willow (Salix sp.)
      Dou, Jinze; Xu, Wenyang; Koivisto, Jari J.; Mobley, Justin K.; Padmakshan, Dharshana; Kogler, Martin; Xu, Chunlin; Willfor, Stefan; Ralph, John; Vuorinen, Tapani
      ACS Sustainable Chemistry & Engineering (2018), 6 (4), 5566-5573CODEN: ASCECG; ISSN:2168-0485. (American Chemical Society)
      Willow bark is a rich source of heterogeneous polyphenolic compds. and a potential feedstock for biorefinery processes aiming at chems. and fiber prodn. Here mild hot water treatment of willow hybrid Karin was studied to find a practical means of isolating its non-cell-wall components for their utilization in a willow biorefinery proposed to aid valorization of the willow biomass. A short aq. treatment of the bark at 80 °C liberated the ext. in >20% yield under unpressurized conditions. The ext. was characterized using mainly gas chromatog.-mass spectrometry and one- and two-dimensional NMR techniques. Authentic analytes were applied to confirm the identification and quantification of the main components that were picein, (+)-catechin, triandrin, glucose, and fructose. Fructose was converted into 5-hydroxymethylfurfural (HMF) in an acidic treatment which led to its condensation with the phenolic components and formation of a recalcitrant ppt. that should be avoided.
    31. 31
      Kesari, K. K.; Dhasmana, A.; Shandilya, S.; Prabhakar, N.; Shaukat, A.; Dou, J.; Rosenholm, J. M.; Vuorinen, T.; Ruokolainen, J. Plant-Derived Natural Biomolecule Picein Attenuates Menadione Induced Oxidative Stress on Neuroblastoma Cell Mitochondria. Antioxidants 2020, 9, 552  DOI: 10.3390/antiox9060552
      31
      Plant-derived natural biomolecule picein attenuates menadione induced oxidative stress on neuroblastoma cell mitochondria
      Kesari, Kavindra Kumar; Dhasmana, Anupam; Shandilya, Shruti; Prabhakar, Neeraj; Shaukat, Ahmed; Dou, Jinze; Rosenholm, Jessica M.; Vuorinen, Tapani; Ruokolainen, Janne
      Antioxidants (2020), 9 (6), 552CODEN: ANTIGE; ISSN:2076-3921. (MDPI AG)
      Several bioactive compds. are in use for the treatment of neurodegenerative disorders, such as Alzheimer's and Parkinson's disease. Historically, willow (salix sp.) bark has been an important source of salisylic acid and other natural compds. with anti-inflammatory, antipyretic and analgesic properties. Among these, picein isolated from hot water ext. of willow bark, has been found to act as a natural secondary metabolite antioxidant. The aim of this study was to investigate the unrevealed pharmacol. action of picein. In silico studies were utilized to direct the investigation towards the neuroprotection abilities of picein. Our in vitro studies demonstrate the neuroprotective properties of picein by blocking the oxidative stress effects, induced by free radical generator 2-methyl-1,4-naphthoquinone (menadione, MQ), in neuroblastoma SH-SY5Y cells. Several oxidative stress-related parameters were evaluated to measure the protection for mitochondrial integrity, such as mitochondrial superoxide prodn., mitochondrial activity (MTT), reactive oxygen species (ROS) and live-cell imaging. A significant increase in the ROS level and mitochondrial superoxide prodn. were measured after MQ treatment, however, a subsequent treatment with picein was able to mitigate this effect by decreasing their levels. Addnl., the mitochondrial activity was significantly decreased by MQ exposure, but a follow-up treatment with picein recovered the normal metabolic activity. In conclusion, the presented results demonstrate that picein can significantly reduce the level of MQ-induced oxidative stress on mitochondria, and thereby plays a role as a potent neuroprotectant.
    32. 32
      Panossian, A.; Hamm, R.; Wikman, G.; Efferth, T. Mechanism of action of Rhodiola, salidroside, tyrosol and triandrin in isolated neuroglial cells: An interactive pathway analysis of the downstream effects using RNA microarray data. Phytomedicine 2014, 21, 1325– 1348,  DOI: 10.1016/j.phymed.2014.07.008
      32
      Mechanism of action of Rhodiola, salidroside, tyrosol and triandrin in isolated neuroglial cells: An interactive pathway analysis of the downstream effects using RNA microarray data
      Panossian, Alexander; Hamm, Rebecca; Wikman, Georg; Efferth, Thomas
      Phytomedicine (2014), 21 (11), 1325-1348CODEN: PYTOEY; ISSN:0944-7113. (Elsevier GmbH)
      The aim of this study was to identify the targets (genes, interactive signaling pathways, and mol. networks) of Rhodiola rosea ext. in isolated neuroglia cells and to predict the effects of Rhodiola ext. on cellular functions and diseases. In addn., the potential mechanism of action of Rhodiola rosea ext. was elucidated, and the "active principle" among the three isolated constituents (salidroside, triandrin, and tyrosol) was identified. Gene expression profiling was performed using the T98G human neuroglia cell line after treatment with the Rhodiola rosea SHR-5 ext. and several of its individual constituents (salidroside, triandrin and tyrosol). An interactive pathway anal. of the downstream effects was performed using datasets contg. significantly up- and down-regulated genes, and the effects on cellular functions and diseases were predicted. In total, the expression of 1062 genes was deregulated by the Rhodiola ext. (631 analyzed, 336 - up-regulated, 295 - down-regulated), and 1052, 1062, and 1057 genes were deregulated by salidroside, triandrin, and tyrosol, resp. The anal. of the downstream effects shows that the most significant effects of Rhodiola are assocd. with cardiovascular (72 deregulated genes), metabolic (63 genes), gastrointestinal (163 genes), neurol. (95 genes), endocrine (60 genes), behavioral (50 genes), and psychol. disorders (62 genes). The most significantly affected canonical pathways across the entire dataset, which contains the 1062 genes deregulated by Rhodiola, were the following: (a) communication between innate and adaptive immune cells, (b) eNOS signaling, (c) altered T and B cell signaling in rheumatoid arthritis, (d) axonal guidance signaling, (e) G-protein coupled receptor signaling, (f) glutamate receptor signaling, (g) ephrin receptor signaling, (h) cAMP-mediated, and (i) atherosclerosis signaling pathways. Genes assocd. with behavior and behavioral diseases were identified within intracellular signaling pathways (d) through (h). The anal. of the downstream effects predicted decreases in emotional and aggressive behavior, which corroborates the results from preclin. and clin. studies of the use of Rhodiola for the treatment of depression and anxiety. Of the 17 genes that regulate emotional behavior, nine exhibit expression patterns that are consistent with decreases in emotional behavior (z-score -2.529), and all five relevant genes are expressed in a manner consistent with decreases in aggressive behavior (z-score -2.197). A decrease in seizures and infarct sizes and an increase in the chemotaxis of cells were predicted to accompany the decrease in emotional and aggressive behaviors. Rhodiola exhibits a multi-targeted effect on transcription to regulate the cellular response, affecting the various signaling pathways and mol. networks assocd. with beneficial effects on emotional behavior, particularly aggressive behavior, and with psychol., neurol., cardiovascular, metabolic, endocrine, and gastrointestinal disorders. Each of the purified compds. has its own pharmacol. profile, which is both similar to and different from that of the total Rhodiola ext. In general, several compds. contribute to the specific cellular or/and physiol. function of the ext. in various diseases.
    33. 33
      Dou, J.; Heinonen, J.; Vuorinen, T.; Xu, C.; Sainio, T. Chromatographic recovery and purification of natural phytochemicals from underappreciated willow bark water extracts. Sep. Purif. Technol. 2021, 261, 118247  DOI: 10.1016/j.seppur.2020.118247
      33
      Chromatographic recovery and purification of natural phytochemicals from underappreciated willow bark water extracts
      Dou, Jinze; Heinonen, Jari; Vuorinen, Tapani; Xu, Chunlin; Sainio, Tuomo
      Separation and Purification Technology (2021), 261 (), 118247CODEN: SPUTFP; ISSN:1383-5866. (Elsevier B.V.)
      Willow (Salicaceae) bark contains a variety of antioxidant phytochems. depending mainly on the hybrid. In this study, hot water extn. of willow bark was coupled with a sequential preparative scale chromatog. to purify the crude exts. to a well-sepd. and highly concd. phytochem. fraction. The pre-equilibrated hydrophilic weak cation exchange resins (with acrylic matrix in Na+ ions form) achieved a good sepn. of phytochems. from monosaccharide fractions. Secondly, the individual phytochem. can be purified based on their size and hydrophobicity differences, using gel permeation chromatog. and adsorption column chromatog. Surprisingly, the G-types of sephadex demonstrated an efficient sepn. of not only monosaccharides but a complete sepn. between (+)-catechin and triandrin. Picein and salicin can be further sepd. according to their hydrophobicity differences. The purified compds. can be quickly quantified using high performance liq. chromatog., gas chromatog. and high-performance anion-exchange chromatog. The purified picein and triandrin were characterized by one- and two-dimensional NMR spectroscopy techniques. Addnl., the authentic compds. were applied to confirm the identification, quantification and purity. The technique described here might be a fast, economical, and highly efficient way in the large-scale isolation and purifn. of the phytochem. compds. from willow bark.
    34. 34
      Sinitsya, A.; Čopíkovά, J.; Pavlíkovά, H. 13C CP/MAS NMR Spectroscopy in the Analysis of Pectins. J. Carbohydr. Chem. 1998, 17, 279– 292,  DOI: 10.1080/07328309808002328
      34
      Carbon-13 CP/MAS NMR spectroscopy in the analysis of pectins
      Sinitsya, Andriy; Copikova, Jana; Pavlikova, Helena
      Journal of Carbohydrate Chemistry (1998), 17 (2), 279-292CODEN: JCACDM; ISSN:0732-8303. (Marcel Dekker, Inc.)
      Carbon-13 CP/MAS NMR spectra of powd. com. pectin (I) samples were recorded and interpreted. NMR spectral results were applied for the calcn. of galacturonic acid (II) content, degrees of methylation (DM) and acetylation (DA). In most cases NMR values from II and DM agreed with values obtained by conventional methods, i.e., photometry and HPLC. The detn. of DA using NMR data was successful only in the case of sugar beet I with high acetyl content. The C-6 carbon region was studied in detail, and the chem. shift and the shape of peaks in this region were strongly influenced by the ratio of uronic carboxyl forms. Correlation between C-6 carbon chem. shift and DM values for I samples in their protonated form was evaluated.
    35. 35
      Koch, H.; Pein, J. Condensation Reactions Between Phenol, Formaldehyde and 5-Hydroxymethylfurfural, Formed as Intermediate in the Acid Catalyzed Dehydration of Starchy Products. Polym. Bull. 1985, 13, 525– 532,  DOI: 10.1007/BF00263474
      35
      Condensation reactions between phenol, formaldehyde and 5-hydroxymethylfurfural, formed as intermediate in the acid catalyzed dehydration of starchy products
      Koch, Helmut; Pein, Joachim
      Polymer Bulletin (Berlin, Germany) (1985), 13 (6), 525-32CODEN: POBUDR; ISSN:0170-0839.
      The incorporation of starch [9005-25-8] hydrolyzates in phenolic resins of the novolak and resol type via intermediate acid catalyzed dehydration to 5-hydroxymethylfurfural (I) was investigated. The course of the reaction was monitored by carbon-13-NMR and IR spectroscopy. Because of the formation of I-phenol condensates, savings of up to 40% phenol and 50% HCHO (by wt.) are possible in comparison to com. resins. Besides maintenance of essential property profiles, addnl. benefits may be achieved with respect to faster curing and lower amts. of free monomers.
    36. 36
      Lopes, M. H.; Gil, A. M.; Silvestre, A. J. D.; Neto, C. P. Composition of Suberin Extracted upon Gradual Alkaline Methanolysis of Quercus suber L. Cork. J. Agric. Food Chem. 2000, 48, 383– 391,  DOI: 10.1021/jf9909398
      36
      Composition of Suberin Extracted upon Gradual Alkaline Methanolysis of Quercus suber L. Cork
      Lopes, Marta H.; Gil, Ana M.; Silvestre, Armando J. D.; Pascoal Neto, Carlos
      Journal of Agricultural and Food Chemistry (2000), 48 (2), 383-391CODEN: JAFCAU; ISSN:0021-8561. (American Chemical Society)
      The monomeric compn. of suberin exts. obtained by gradual alk. methanolysis of Quercus suber cork was detd. by gas chromatog.-mass spectrometry (GC-MS). Results show that 1-alkanols and alkanoic and α,ω-alkanedioic acids are preferentially removed upon mild alk. conditions, whereas mid-chain-modified ω-hydroxyalkanoic acids are preferentially removed under stronger alk. conditions. Satd. ω-hydroxyalkanoic acids are found to be abundant in all suberin exts. These results are consistent with two distinct suberin fractions with different locations in cork cell walls and/or esterification degrees. It is proposed that these fractions correlate with the two main suberin peaks in the solid state 13C NMR spectra of cork and suberin exts. Quant. GC-MS anal. showed that suberin monomers comprise ∼30% (wt./wt.) of the suberin exts., the remaining comprising nonvolatile structures with high Mn values, as measured by vapor pressure osmometry. The presence of a large fraction of high mol. wt. aliph. structures in suberin exts. is supported by the corresponding NMR spectra.
    37. 37
      Rojo, E.; Peresin, M. S.; Sampson, W. W.; Hoeger, I. C.; Vartiainen, J.; Laine, J.; Rojas, O. J. Comprehensive elucidation of the effect of residual lignin on the physical, barrier, mechanical and surface properties of nanocellulose films. Green Chem. 2015, 17, 1853– 1866,  DOI: 10.1039/C4GC02398F
      37
      Comprehensive elucidation of the effect of residual lignin on the physical, barrier, mechanical and surface properties of nanocellulose films
      Rojo, Ester; Peresin, Maria Soledad; Sampson, William W.; Hoeger, Ingrid C.; Vartiainen, Jari; Laine, Janne; Rojas, Orlando J.
      Green Chemistry (2015), 17 (3), 1853-1866CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
      We elucidate the effect of residual lignin on the interfacial, phys. and mech. properties of lignocellulose nanofibrils (LCNF) and resp. nanopapers. Fibers contg. ∼0, 2, 4, and 14 wt% residual lignin were microfluidized into LCNF aq. suspensions and were processed into dry films (nanopapers). A systematic decrease in fibril diam. with increasing residual lignin was obsd. upon fibrillation, consistent with the radical scavenging ability of the lignin that results in better cell wall deconstruction. The stiff nature of the lignin-contg. fibrils made them less able to conform during filtration and improved extensively dewatering, owing to a more open structure. However, the softening of the lignin during hot-pressing of the nanopapers and its amorphous nature enabled a binding effect, filling the voids between the nanofibers (thus reducing the no. of micropores) and making the surface of the nanopapers smoother. The interfacial free energy of interaction changed drastically with the increased lignin content: the corresponding water contact angles were 35° and 78° for the lignin-free and for the (14%) lignin-contg. nanopaper, resp., revealing the increase in hydrophobicity. Together with the significantly less porous structure of LCNF nanopapers, lower water absorbency was obsd. with increased lignin content. Lignin in the nanopapers reduced the oxygen permeability by up to 200-fold. Water vapor permeability, in turn, did not correlate linearly with lignin content but depended most significantly on material d. The tensile strength, modulus, and strain for the LCNF nanopapers were found to be in the range 116-164 MPa, 10.5-14.3 GPa, and 1.7-3.5%, resp. To a good degree of approxn., these mech. properties were rather insensitive to lignin content and comparable to those of nanopapers derived from fully bleached CNF. While it might be expected that lignin interferes in hydrogen bonding between fibrils, this was apparently counteracted by the uniform distribution of lignin seemingly aiding stress-transfer between fibrils and thus preserving mech. properties. Overall, LCNF is demonstrated to be a suitable precursor of nanopaper, esp. when reduced polarity and low hydrophilicity are desirable in related bio-products.
    38. 38
      Rindlav-Westling, Å.; Stading, M.; Hermansson, A.; Gatenholm, P. Structure, mechanical and barrier properties of amylose and amylopectin films. Carbohydr. Polym. 1998, 36, 217– 224,  DOI: 10.1016/S0144-8617(98)00025-3
      38
      Structure, mechanical and barrier properties of amylose and amylopectin films
      Rindlav-Westling, Asa; Stading, Mats; Hermansson, Anne-Marie; Gatenholm, Paul
      Carbohydrate Polymers (1998), 36 (2/3), 217-224CODEN: CAPOD8; ISSN:0144-8617. (Elsevier Science Ltd.)
      The effect of film formation conditions on structure, mech. properties, and barrier properties of amylose (I) and amylopectin (II) films was studied. The films were prepd. by soln.-gel-casting of I and II from potato, with or without the addn. of glycerol (III) as plasticizer. Transmission electron micrographs showed that the network structure characteristic for the I gel was also found in the film state. The I films without III plasticization exhibited a relatively high degree of B-type crystallinity, as revealed by wide-angle x-ray diffraction, whereas the unplasticized II films were amorphous. Although the addn. of III did not affect the crystallinity of the I films, III-plasticized II formed B-type crystallinity, and the degree of crystallinity was dependent on the air humidity during film formation. The degree of crystallinity affected the mech. properties of the II films, whereas the mech. properties of the I films were influenced by the network microstructure. O and water vapor permeabilities were dependent neither on the degree of crystallinity in the films nor on the network structure.
    39. 39
      Miller, K. S.; Krochta, J. M. Oxygen and aroma barrier properties of edible films: A review. Trends Food Sci. Technol. 1997, 8, 228– 237,  DOI: 10.1016/S0924-2244(97)01051-0
      39
      Oxygen and aroma barrier properties of edible films: a review
      Miller, K. S.; Krochta, J. M.
      Trends in Food Science & Technology (1997), 8 (7), 228-237CODEN: TFTEEH; ISSN:0924-2244. (Elsevier)
      A review with 73 refs. Interest in maintaining food quality while reducing packaging waste has encouraged the exploration of the oxygen and aroma transport properties of edible films. This review article introduces the theor. basis for oxygen and aroma barrier property detn. and presents a brief historical perspective of the development of barrier polymers. The effects of structure and compn. on mass transport in edible films are examd. and compared with those of the more thoroughly investigated synthetic polymers. A survey of edible film oxygen and aroma barrier research is presented; areas requiring addnl. investigation are suggested, for applications as well as basic research.
    40. 40
      Shimizu, M.; Saito, T.; Isogai, A. Water-resistant and high oxygen-barrier nanocellulose films with interfibrillar cross-linkages formed through multivalent metal ions. J. Membr. Sci. 2016, 500, 1– 7,  DOI: 10.1016/j.memsci.2015.11.002
      40
      Water-resistant and high oxygen-barrier nanocellulose films with interfibrillar cross-linkages formed through multivalent metal ions
      Shimizu, Michiko; Saito, Tsuguyuki; Isogai, Akira
      Journal of Membrane Science (2016), 500 (), 1-7CODEN: JMESDO; ISSN:0376-7388. (Elsevier B.V.)
      Once-dried 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibril (TOCN) films with sodium carboxylate groups (TOCN-COONa) were soaked in aq. MgCl2, CaCl2, AlCl3 and FeCl3 solns. to change the counterion to TOCNs-COOM films (M: metal ion). Dry TOCN-COOM films had high Young's moduli (11-20 GPa) and tensile strength (170-280 MPa). In particular, the wet TOCN films with aluminum and iron (III) carboxylates had high Young's moduli and tensile strengths of ∼3 GPa and 30-40 MPa, resp., even at water contents of ∼470%. Moreover, the dry TOCN films with calcium and aluminum carboxylates had extremely low oxygen permeabilities of 0.08 and 0.15 mL μm m-2 day-1 kPa-1, resp., even at 80% relative humidity, which are outstanding values compared to those of other films reported previously. These results are explained in terms of the high water resistance of the films, which is caused by the formation of interfibrillar crosslinkages through multivalent metal ions.
    41. 41
      Medina Jaramillo, C.; Seligra, P. G.; Goyanes, S.; Bernal, C.; Famά, L. Biofilms based on cassava starch containing extract of yerba mate as antioxidant and plasticizer. Starch 2015, 67, 780– 789,  DOI: 10.1002/star.201500033
      41
      Biofilms based on cassava starch containing extract of yerba mate as antioxidant and plasticizer
      Medina Jaramillo, Carolina; Gonzalez Seligra, Paula; Goyanes, Silvia; Bernal, Celina; Fama, Lucia
      Starch/Staerke (2015), 67 (9-10), 780-789CODEN: STARDD; ISSN:0038-9056. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Cassava starch based films contg. different concns. of yerba mate ext. as antioxidant (0, 5, and 20%) were prepd. by casting. The effect of the incorporation of the ext. on the antioxidant activity, structure, and physicochem. properties of the biofilms was evaluated. Significant antioxidant capacity in the films with yerba mate ext. was obtained, esp. in the materials contg. 5% of the additive. The surface roughness and contact angle of the systems contg. the ext. increased, indicating hydrophobic behavior of the films surface when the additive was used. This was also confirmed by water vapor permeability and water content results. The incorporation of yerba mate ext. led to an important improvement in the elasticity of the biofilms, as well as to a shift of the relaxations assocd. with the glycerol-rich and starch-rich phases to lower temp. values, revealing a typical behavior of a plasticized film. The relevant antioxidant and plasticizing effects of yerba mate ext. on cassava starch films make them promising to be used as coatings or packaging in the food industry.
    42. 42
      Baumberger, S.; Lapierre, C.; Monties, B. Utilization of Pine Kraft Lignin in Starch Composites: Impact of Structural Heterogeneity. J. Agric. Food Chem. 1998, 46, 2234– 2240,  DOI: 10.1021/jf971067h
      42
      Utilization of Pine Kraft Lignin in Starch Composites: Impact of Structural Heterogeneity
      Baumberger, S.; Lapierre, C.; Monties, B.
      Journal of Agricultural and Food Chemistry (1998), 46 (6), 2234-2240CODEN: JAFCAU; ISSN:0021-8561. (American Chemical Society)
      To elucidate the effect of lignin structure on the properties of lignin-starch composites, an industrial pine kraft lignin sample was fractionated by sequential extn. with org. solvents. Three fractions were obtained with different carbohydrate contents, IR spectra, and mol. size distributions. In addn., an in-depth structural investigation was performed by GC-MS analyses of the low-mol. wt. phenolics occurring in the native fractions or obtained by thioacidolysis. The properties of the lignin-starch composites made from pine kraft lignin or its fractions were evaluated, as compared to ref. starch films. Although present in small quantities, the low-mol. wt. fraction isolated from pine kraft lignin was obsd. to have a key role in the mech. properties of the films, mainly as a starch plasticizer.
    43. 43
      Espinosa, E.; Bascón-Villegas, I.; Rosal, A.; Pérez-Rodríguez, F.; Chinga-Carrasco, G.; Rodríguez, A. PVA/(ligno)nanocellulose biocomposite films. Effect of residual lignin content on structural, mechanical, barrier and antioxidant properties. Int. J. Biol. Macromol. 2019, 141, 197– 206,  DOI: 10.1016/j.ijbiomac.2019.08.262
      43
      PVA/(ligno)nanocellulose biocomposite films. Effect of residual lignin content on structural, mechanical, barrier and antioxidant properties
      Espinosa, Eduardo; Bascon-Villegas, Isabel; Rosal, Antonio; Perez-Rodriguez, Fernando; Chinga-Carrasco, Gary; Rodriguez, Alejandro
      International Journal of Biological Macromolecules (2019), 141 (), 197-206CODEN: IJBMDR; ISSN:0141-8130. (Elsevier B.V.)
      Nanocelluloses with and without residual lignin were isolated from wheat straw. In addn., the effect of TEMPO-mediated oxidn. on the prodn. of lignin-contg. nanocellulose was studied. The different nanocelluloses were used as reinforcing agent in poly(vinyl alc.) films. The morphol., crystallinity, surface microstructure, barrier properties, light transmittance, mech. and antioxidant properties were evaluated. The translucency of films was reduced by the addn. of nanocellulose, however, the ability to block UV-light increased from 10% for PVA to >50% using lignin-contg. nanocellulose, and 30% for lignin-free samples. The mech. properties increased considerably, however, for loads higher than 5% a neg. trend was obsd. presumptively due to a clustering of nanocellulose components in PVA matrix. The barrier properties of the films were improved with the use of nanocellulose, esp. at small amts. (1-3%). The antioxidant capacity of films was increased up to 10% using lignin-contg. nanocellulose compared to 4.7% using PVA.
    44. 44
      De Simone, O. D.; Haase, K.; Müller, E.; Junk, W. J.; Hartmann, K.; Schreiber, L.; Schmidt, W. Apoplasmic Barriers and Oxygen Transport Properties of Hypodermal Cell Walls in Roots from Four Amazonian Tree Species. Plant Physiol. 2003, 132, 206– 217,  DOI: 10.1104/pp.102.014902
      44
      Apoplasmic barriers and oxygen transport properties of hypodermal cell walls in roots from four Amazonian tree species
      De Simone, Oliviero; Haase, Karen; Muller, Ewald; Junk, Wolfgang J.; Hartmann, Klaus; Schreiber, Lukas; Schmidt, Wolfgang
      Plant Physiology (2003), 132 (1), 206-217CODEN: PLPHAY; ISSN:0032-0889. (American Society of Plant Biologists)
      The formation of suberized and lignified barriers in the exodermis is suggested to be part of a suite of adaptations to flooded or waterlogged conditions, adjusting transport of solutes and gases in and out of roots. In this study, the compn. of apoplasmic barriers in hypodermal cell walls and oxygen profiles in roots and the surrounding medium of four Amazon tree species that are subjected to long-term flooding at their habitat was analyzed. In hypodermal cell walls of the deciduous tree Crateva benthami, suberization is very weak and dominated by monoacids, 2-hydroxy acids, and ω-hydroxycarboxylic acids. This species does not show any morphol. adaptations to flooding and overcomes the aquatic period in a dormant state. Hypodermal cells of Tabernaemontana juruana, a tree which is able to maintain its leaf system during the aquatic phase, are characterized by extensively suberized walls, incrusted mainly by the unsatd. C18 ω-hydroxycarboxylic acid and the α,ω-dicarboxylic acid analogon, known as typical suberin markers. Two other evergreen species, Laetia corymbulosa and Salix martiana, contained 3- to 4-fold less aliph. suberin in the exodermis, but more than 85% of the arom. moiety of suberin are composed of para-hydroxybenzoic acid, suggesting a function of suberin in pathogen defense. No major differences in the lignin content among the species were obsd. Detn. of oxygen distribution in the roots and rhizosphere of the four species revealed that radial loss of oxygen can be effectively restricted by the formation of suberized barriers but not by lignification of exodermal cell walls.
    45. 45
      Korpinen, R. I.; Kilpeläinen, P.; Sarjala, T.; Nurmi, M.; Saloranta, P.; Holmbom, T.; Koivula, H.; Mikkonen, K. S.; Willför, S.; Saranpää, P. T. The Hydrophobicity of Lignocellulosic Fiber Network Can Be Enhanced with Suberin Fatty Acids. Molecules 2019, 24, 4391  DOI: 10.3390/molecules24234391
      45
      The hydrophobicity of lignocellulosic fiber network can be enhanced with suberin fatty acids
      Korpinen, Risto I.; Kilpelainen, Petri; Sarjala, Tytti; Nurmi, Maristiina; Saloranta, Pauliina; Holmbom, Thomas; Koivula, Hanna; Mikkonen, Kirsi S.; Willfor, Stefan; Saranpaa, Pekka T.
      Molecules (2019), 24 (23), 4391CODEN: MOLEFW; ISSN:1420-3049. (MDPI AG)
      Suberin fatty acids were extd. from outer bark of Silver birch (Betula pendula Roth.) using an isopropanolic sodium hydroxide soln. Lab. sheets composed of lignocellulosic fiber networks were prepd. from unbleached and unrefined softwood kraft pulp and further impregnated with suberin fatty acid monomers and cured with maleic anhydride in ethanol soln. The treatment resulted in hydrophobic surfaces, in which the contact angles remained over 120 degrees during the entire measurement. The fiber network also retained its water vapor permeability and enhanced fiber-fiber bonding resulted in improved tensile strength of the sheets. SEM (SEM) images revealed that the curing agent, together with suberin fatty acids, was evenly distributed on the fiber surfaces and smoothing occurred over the wrinkled microfibrillar structure. High concns. of the curing agent resulted in globular structures contg. betulinol derivates as revealed with time-of-flight secondary ion mass spectrometry (ToF-SIMS). Also, the larger amt. of suberin fatty acid monomers slightly impaired the optical properties of sheets.
    46. 46
      Liu, X.; Wang, J.; Li, S.; Zhuang, X.; Xu, Y.; Wang, C.; Chu, F. Preparation and properties of UV-absorbent lignin graft copolymer films from lignocellulosic butanol residue. Ind. Crops Prod. 2014, 52, 633– 641,  DOI: 10.1016/j.indcrop.2013.11.036
      46
      Preparation and properties of UV-absorbent lignin graft copolymer films from lignocellulosic butanol residue
      Liu, Xiaohuan; Wang, Jifu; Li, Shouhai; Zhuang, Xiaowei; Xu, Yuzhi; Wang, Chunpeng; Chu, Fuxiang
      Industrial Crops and Products (2014), 52 (), 633-641CODEN: ICRDEW; ISSN:0926-6690. (Elsevier B.V.)
      The aim of this study was to develop economically UV-absorbent and visible-transparent films. For this purpose, lignin was selected because of its strong UV absorbing property. Lignocellulosic butanol residue, as the byproduct of lignocellulosic butanol prodn., is rich in biobutanol lignin (BBL). Herein, BBL was modified with acryloyl chloride and then copolymd. with Bu acrylate (BA) and Me methacrylate (MMA) by free-radical polymn. The chem. structure of poly(BA-co-MMA) chains was identifiable by 1H NMR and 13C NMR spectroscopies, combined with UV-visible spectra to confirm the existence of the arom. groups that are attributed to BBL in the copolymer. This provided evidence that a BBL graft copolymer was successfully synthesized. The optical, photo-stability, chem. resistance, thermal and mech. properties of the copolymer were evaluated. The copolymer film can absorb 96.2% of UV light, while allowing 70% or higher transmittance in the visible spectrum when the surface concn. of BBL-AC was 240U+03BCg cm-2. In addn., the copolymer film retained excellent absorption capacity in the UV region and high transparency in the visible light region after 75 min continuous UV-irradn. or when heated at 100U+00B0C, rendering it potential to use as a UV-absorbent film. The copolymer exhibited good chem. resistance, thermal and mech. properties compared with pure poly(BA-co-MMA). This strategy not only provides a novel approach for UV-absorbent films but also greatly extends the comprehensive utilization of BBL.
    47. 47
      Gierer, J.; Lin, S. Y. Photodegradation of lignin. A contribution to the mechanism of chromophore formation. Sven. Papperstidn. 1972, 75, 233– 237
      47
      Photodegradation of lignin. Mechanism of chromophore formation
      Gierer, Josef; Lin, Stephen Y.
      Svensk Papperstidning (1972), 75 (7), 233-9CODEN: SVPAAE; ISSN:0283-6831.
      The photochem. cleavage of phenacyl aryl ether linkages is examd., and the significance of this reaction in the light-induced discoloration and degradation of lignin is discussed. Lignin is stabilized by the redn. or epoxidation of carbonyl groups and the etherification of phenolic hydroxyls.

  • Supporting Information

    Supporting Information

    The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsanm.1c00071.

    • Analytical process scheme for preparing samples for chemical composition analysis from willow bark and HWEWB together with their fibril samples; overall chemical composition and carbohydrate composition of the experimental samples; solid-state 13C CP/MAS spectrum of the LCNF fibrils and its associated HMW; HSQC NMR spectra of the dissolved and precipitated HMW fraction in comparison with the enzymatically isolated Karin bark lignin; SEM images of the associated LCNF films; the water contact angle images show the shape of water droplets on the LCNF fibril networks and films; quantitative AFM measurements illustrating the height image of the studied fibrils; ultraviolet (UV) transmittance of the produced LCNF films (PDF)


    Terms & Conditions

    Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.