Biotransformation of soy whey into soy alcoholic beverage by four commercial strains of Saccharomyces cerevisiae

Soy whey is a liquid waste stream generated from tofu and soy protein manufacturing, and is commonly disposed of into the drainage system in food industry. Instead of disposing of soy whey as a waste, it could be used to produce alcoholic beverages. This study investigated the feasibility of converting soy whey into soy alcoholic beverage using four commercial Saccharomyces cerevisiae strains as a zero-waste approach to tackle the soy whey disposal issue. The four Saccharomyces yeasts grew by approximately 2 log CFU/mL and produced approximately 7-8% (v/v) of ethanol. Isoflavone glucosides were hydrolyzed and transformed into isoflavone aglycones, increasing the antioxidant capacity. New aroma-active volatiles, especially esters and higher alcohols, were produced and imparted fruity and floral notes to the soy alcoholic beverage. Therefore, alcoholic fermentation would serve as a solution toward zero-waste manufacturing by biotransforming soy whey into a world's first novel functional alcoholic beverage naturally enriched with free isoflavones.