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Heat-Induced Changes in Myofibrillar Protein Structures and Myowater of Two Pork Qualities. A Combined FT-IR Spectroscopy and Low-Field NMR Relaxometry Study

Hanne Christine Bertram,*^† Achim Kohler,^‡ Ulrike Böcker,^‡ Ragni Ofstad,^‡ and Henrik J. Andersen^†

Department of Food Science, Danish Institute of Agricultural Sciences, Research Centre Foulum, P.O. Box 50, DK-8830 Tjele, Denmark, and MATFORSK, Norwegian Food Research Institute, Osloveien 1, N-1430 s, Norway

J. Agric. Food Chem., 2006, 54 (5), pp 1740–1746

DOI: 10.1021/jf0514726

Publication Date (Web): February 7, 2006

To whom correspondence should be addressed. Phone: +45 89 99 15 06. Fax: +45 89 99 15 64. E-mail: HanneC.Bertram@agrsci.dk.

†

Research Centre Foulum.

‡

Norwegian Food Research Institute.

Abstract

Low-field NMR T₂ and Fourier transform infrared (FT-IR) measurements were performed on meat samples of two qualities (normal and high ultimate pH) during cooking from 28 °C to 81 °C. Pronounced changes in both T₂ relaxation data and FT-IR spectroscopic data were observed during cooking, revealing severe changes in the water properties and structural organization of proteins. The FT-IR data revealed major changes in bands in the amide I region (1700−1600 cm^-¹), and a tentative assignment of these is discussed. Distributed NMR T₂ relaxation data and FT-IR spectra were compared by partial least-squares regression. This revealed a correlation between the FT-IR peaks reflecting β-sheet and α-helix structures and the NMR relaxation populations reflecting hydration water (T_2B 0−10 ms), myofibrillar water (T₂₁ 35−50 ms), and also expelled “bulk” water (T₂ relaxation times >1000 ms). Accordingly, the present study demonstrates that definite structural changes in proteins during cooking of meat are associated with simultaneous alterations in the chemical−physical properties of the water within the meat.

Keywords: Water distribution; muscle; protein denaturation; cooking; multivariate data analysis

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Published In Issue March 08, 2006
Received for review June 22, 2005. Revised manuscript received December 1, 2005. Accepted December 8, 2005. We thank The Danish Ministry of Food, Agriculture and Fisheries for funding the project entitled “Characterisation of technological and sensory quality in foods”, the Danish Research Council SJVF for funding the project “Characterization of basic NMR properties in perimortal muscles and meat in relation to physical and metabolic changes”, and the Norwegian research council, who supported this study through Grant No. 15338/140.