Impact of lactic acid bacterial strain and storage temperature on the quality and functionality of fermented mulberry juice

This study systematically analyzes the differences in quality parameters and volatile flavor compounds of mulberry juice fermented with Lactobacillus plantarum (LPJ) and Lactobacillus delbrueckii subsp. bulgaricus (LBJ) during storage at room temperature (25 °C) and 4 °C. Lactic acid fermentation reduced sugar content, pH, and protein levels. After fermentation, the total phenol, total flavonoid, and total anthocyanin contents, along with antioxidant activity, were enhanced. However, the levels of active compounds declined during storage, with a slower decline observed at 4 °C. The LPJ group exhibited superior antioxidant activity. A total of 144 flavor compounds were identified, with the variety and abundance of volatile compounds increasing after fermentation compared to unfermented mulberry juice. After 21 days of storage, the number of volatile compounds decreased to 120, with a notable reduction in ester and aldehyde contents. Crude polysaccharides from LPJ-fermented mulberry juice showed significant ethanol dehydrogenase and hypoglycemic activities, supporting the medicinal potential of mulberries.