Abstract: This study evaluated the β-glucosidase activities of 10 strains of Lactobacillus plantrum, L. helveticus, L. pentosus, and Streptococcus thermophilus) and compared the fermentation performance of the strains and the antioxidant properties and flavor quality of soymilk fermented by each of these strains. Moreover, the contents of isoflavones in fermented soymilk were analyzed. The results showed differences in the β-glucosidase activity of the different LABs, all of which showed good growth in soymilk, and L. plantarum was more suitable for growth in soymilk. LAB fermentation promoted the conversion of soybean isoflavones to active aglycones, and improved the nutritional characteristics of soymilk. Meanwhile, LAB changed the composition and content of volatile components, and effectively reduced the contents of hexanal, nonanal and 2-pentylfuran, which have been reported to be responsible for beany flavor, while retaining the characteristic aroma compounds of soymilk. Strains LPL044 and LPL051, with the highest β-glucosidase activity, showed the strongest ability to convert soymilk isoflavones, and the fermented soymilk had the highest contents of total phenols and total flavonoids, the strongest antioxidant activity and the best sensory quality, so they have greater research and development value compared with the other LABs.

Key words: lactic acid bacteria; soymilk; β-glucosidase; isoflavone; antioxidant activity; volatile flavor components