Effects of okara and vitamin B2 bioenrichment on the functional properties and in vitro digestion of fermented soy milk

• Published in: Food research international Vol. 145; p. 110419
• Main Authors: Feng, Jing-Yu, Thakur, Kiran, Ni, Zhi-Jing, Zhu, Yun-Yang, Hu, Fei, Zhang, Jian-Guo, Wei, Zhao-Jun
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.07.2021
• Subjects: Fermentation; In vitro digestion; Lactobacillus; Okara; Riboflavin; Soy milk; Riboflavin; Soy milk; In vitro digestion; Fermentation; Okara; Lactobacillus
• ISSN: 0963-9969; 1873-7145
• DOI: 10.1016/j.foodres.2021.110419

[Display omitted] •Okara immobilized B2 vitamin producing probiotic lactobacilli UFG10 could improve the functional properties of soymilk.•Okara immobilization not only allowed the bacterial protection but also elevated their metabolism.•Enhanced aglycone isoflavones release and improved B2 production were reported in the soymilk.•Okara immobilized B2 producing lactobacilli improved the antioxidant status of soymilk.•AFM revealed higher soy protein aggregation and lower protein molecular chains indicating better digestibility. Due to highly nutritious and well-known prebiotic nature, okara (soy by-product) can improve the physiological benefits of probiotic consumption by enhancing the physicochemical stability and bioavailability of bacteria and metabolites, partially in food matrices and then in gastrointestinal tract. Initially, vitamin B2 producing probiotic Lactobacillus plantarum UFG10 was immobilized with 4% okara for soy milk fermentation. SEM micrographs showed firm adherence of UFG10 to okara surface depicting efficient immobilization. Soy milk fermented with okara immobilized UFG10 showed enhanced β-glucosidase activity, stimulating the biotransformation of isoflavones from glucosides (daidzin, from 27.78 to 9.84 μg/mL; genistin, from 32.58 to 8.33 μg/mL) to aglycones (daidzein, from 0.19 to 30.84 μg/mL; genistein, from 1.42 to 33.10 μg/mL) and higher B2 production (1.53 μg/mL, 12 h) confirmed by HPLC. Okara addition and B2 enrichment could yield relatively higher antioxidant strength than control soy milk. PLSR correlation revealed the effects of okara and B2 on the functional properties of soy milk. After okara immobilization, soy milk showed higher soy protein digestibility after in vitro digestion for 225 min, higher aggregation, and lower protein molecular chains, qualitatively confirmed with Atomic force microscope. Okara immobilized bacterial cells exhibited relatively greater resistance up to 55.1% (p < 0.05) in simulated GIT, indicating okara as an ideal substrate for an efficient immobilization which ultimately improved the fate of soy B2 and protein bioaccessibility and functional products such as isoflavones for micro structural design of soy milk with improved nutrition and digestibility.