Insights into the improvement of bioactive phytochemicals, antioxidant activities and flavor profiles in soy whey fermented by various native lactic acid bacteria.

Soy whey, a tofu production byproduct rich in nutrients, is typically discarded. This study investigated five natural lactic acid bacteria (LAB) strains isolated from spontaneously fermented soy whey (FSW) for their fermentation performance in soy whey medium. The growth characteristics, total phenols and flavonoids compounds, antioxidant activities, and aroma profiles were evaluated. The results demonstrated that all five LAB strains exhibited excellent adaptability in soy whey fermentation. After fermentation, the total phenols and flavonoids compounds increased, total isoflavone glycosides (daidzin, glycitin and genistin) decreased by 38-47%, while their corresponding aglycones (daidzein, glycitein, and genistein) significantly increased to 36.38-40.52 mg/L, resulting in improved bioavailability. A total of 33 volatile compounds were identified, Off-flavors like hexanal (beany odor) decreased, while new esters (ethyl hexanoate and butyl acetate) enhanced the flavor profile. Sensory evaluation showed LAB fermentation improved soy whey's taste, texture and acceptability, with strain 3-1 performing best. Results demonstrate LAB fermentation effectively reduces anti-nutritional factors while enhancing functionality and palatability, supporting fermented soy whey's potential as a functional beverage. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-025-04500-5.