Changes in conjugated linoleic acid and isoflavone contents from fermented soymilks using Lactobacillus plantarum P1201 and screening for their digestive enzyme inhibition and antioxidant properties

This research was the first to investigate the variations of conjugated linoleic acid (CLA), isoflavone, digestive enzyme inhibition, and antioxidant properties in hydrolysate soybean milks under fermentation using Lactobacillus plantarum P1201. The average CLA contents increased significantly in the range of ND → 0.91-1.75 mg/g during fermentation, whereas the isoflavone glucosides were markedly reduced (1570.01 → 548.41 µg/g, 65%) with the increase of aglycone contents (58.75 → 453.45 µg/g, 7.7 times). In particular, daidzein and cis-9, trans-11 CLA exhibited the predominant compositions (>50% and >90%) with considerable increases in fermented soybean milks. Total phenolic and flavonoid contents also slightly increased. Interestingly, fermented soybean extracts possessed potent α-glucosidase and pancreatic lipase inhibitory effects with average 32.4 → 55.5% and ND → 43.4% at a concentration of 500 μg/ml. Moreover, the antioxidant properties against three radicals increased markedly as the following order: ABTS (46.1 → 87.6%) > DPPH (38.8 → 77.4%) > hydroxyl (15.6 → 47.0%). Therefore, fermented hydrolysate milks might have attributed to enhance the soybean value.