VALORISATION OF SOYBEAN RESIDUE (OKARA) BY YEAST FERMENTATION

VONG WENG CHAN

Publication

VALORISATION OF SOYBEAN RESIDUE (OKARA) BY YEAST FERMENTATION

VONG WENG CHAN

Abstract

Okara (soybean residue) is a food processing by-product from soymilk and tofu manufacture. This work explored the impact of yeast fermentation on the nutritional and volatile profiles of okara. Wine yeast Lindnera saturnus significantly increased the amount of esters in okara due to reactions between endogenous soy lipoxygenases, soy lipids, yeast enzymes and yeast metabolites. Dairy yeast Yarrowia lipolytica catabolised the lipid and protein fractions in okara, leading to greater amounts of succinate and free amino acids. Additionally, fungus (Rhizopus oligosporus) and carbohydrase (cellulase and hemicellulase) pre-treatments were evaluated for their effectiveness in complementing yeast fermentation. The pre-treatments significantly reduced the amount of insoluble fibre and converted isoflavone glycosides into aglycones. These findings lent to the development of an okara-based probiotic beverage using carbohydrase, yeast L. saturnus and probiotic Lactobacillus paracasei. As shown, yeasts can be used in combination with other microbes and/or enzymes for the complete valorisation of okara.