Chemical Compositions and Physicochemical Properties of the Fiber-Rich Materials Prepared from Shoyu Mash Residue

Fiber-rich materials including desalted shoyu mash residue (briefly referred as desalted mash residue, DMR), alcohol-insoluble solid (AIS), and water-insoluble solid (WIS) were prepared from shoyu mash residue, which is a filtration cake obtained during the isolation of shoyu by press filtration of fermented matrix in the final process. The DMR, AIS, and WIS contain rich dietary fiber of 52.4, 61.5, and 54.7 wt %, respectively. The DMR, AIS, and WIS all have significantly lower bulk densities, and higher water-holding capacities, oil-holding capacities, swelling abilities, and cation-exchange capacities than the control cellulose. These results indicated that the said fiber-rich materials prepared in this study all have the desired physicochemical properties for being used as satisfactory sources of dietary fibers or low-calorie bulk ingredients in food applications requiring oil and moisture retention. Furthermore, the said fiber-rich materials also have high contents of isoflavones, mainly daidzein and genistein, which are considered as the most bioavailable phytoestrogens, with a total amount of about 1200−1480 μmol/100 g (equal to daidzein of ca. 3040−3759 μg/g, or genistein of 3240−3996 μg/g). The results revealed that the said fiber-rich materials might be a potent fiber source for health foods.

Keywords: Soy sauce; shoyu mash residue; chemical composition; dietary fiber; physicochemical properties; isoflavones