Compositional Changes and Physical Properties of Soymilk Prepared with Pre-soaked-fermented Soybean
Kim, D.M., Sejong University, Seoul, Republic of Korea | Lee, H.S., Sejong University, Seoul, Republic of Korea | Yoo, S.H., Sejong University, Seoul, Republic of Korea
Effect of lactic acid bacteria-fermented whey in the soybean soaking process of the soymilk production was investigated to minimize bacterial contamination and increase isoflavone and γ-amino butyric acid (GABA) concentrations. Mixed culture of Lactobacillus acidophilus, Bifidobacterium lactis, and Streptococcus thermophilus displayed the highest β-glucosidase activity and was used for the production of health functional soymilk. A significant pH reduction from 6.75 to 5.19 was observed in soymilk product, whereas its titratable acidity increased from 0.18 to 0.24% after 24-h soaking of soybean in fermented whey. Suspension stability of soymilk dramatically dropped between 18- and 24-h soaking periods, largely due to pH reduction, which reflected decrease in solid contents of soymilk from 7.38 to 1.54%. Total isoflavone content significantly decreased with increasing soaking time in the fermented whey, whereas the content of health-beneficial aglycone increased by three fold (0.27 mg/100 mL of soymilk) after 18-h soaking fermentation. The contents of free amino acids (6.0 mg → 2.3 mg/100 mL) and GABA (1.1 mg → 0.5 mg) in soymilk were reduced in soymilks produced with the fermented soybeans between 18- and 24-h soaking periods. The pH-drop induced solid precipitation, which could exert negative effect on the free amino acid and GABA contents in fermented soymilk.
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