Conversion of Isoflavone Glucosides to Aglycones in Soymilk by Fermentation with Lactic Acid Bacteria

• Published in: Journal of food science 2007-03, Vol.72 (2), p.M39-M44
• Main Authors: Chun, Jiyeon, Kim, Gyoung Min, Lee, Kang Wook, Choi, In Duck, Kwon, Gun-Hee, Park, Jae-Young, Jeong, Seon-Ju, Kim, Jeong-Sang, Kim, Jeong Hwan
• Format: Article
• Language: English
• Subjects: Bacteria; beta-Glucosidase - metabolism; Biological and medical sciences; Chemical reactions; Colony Count, Microbial; daidzein; daidzin; Enterococcus durans; Fermentation; fermented foods; Food Handling - methods; Food industries; Food Microbiology; Food Preservation - methods; Food science; Fundamental and applied biological sciences. Psychology; genistein; genistin; Glucose; Glucosides - metabolism; glycitin; Hydrogen-Ion Concentration; hydrolysis; isoflavones; Isoflavones - analysis; Isoflavones - biosynthesis; lactic acid bacteria; lactic fermentation; Lactobacillus - growth & development; Lactobacillus - metabolism; Lactobacillus paraplantarum; microbial growth; Soy Milk - chemistry; Soy products; soymilk; starter cultures; Streptococcus salivarius; Temperature; Time Factors; titratable acidity; Weissella confusa
• ISSN: 0022-1147; 1750-3841
• DOI: 10.1111/j.1750-3841.2007.00276.x

Four lactic acid bacteria (LAB), Lactobacillus paraplantarum KM, Enterococcus durans KH, Streptococcus salivarius HM and Weissella confusa JY, were isolated from humans and tested for their capabilities of converting isoflavone glucosides to aglycones in soymilk. Changes in growth, pH, and titratable acidity (TA) were investigated during fermentation at 37 °C for 12 h. After 6 to 9 h of fermentation, each population of 4 LAB reached 10⁸ to 10⁹ CFU/mL. The initial pH of 6.3 ± 0.1 decreased while the TA of 0.13%± 0.01% increased as fermentation proceeded, resulting in the final range between 4.1 ± 0.2 and 4.6 ± 0.1 for pH and between 0.51%± 0.02% and 0.67%± 0.06% for TA after the 12 h of fermentation. The glucoside concentrations were significantly decreased in soymilks fermented with either L. paraplantarum KM, S. salivarius HM, or W. confusa JY with fermentation time (P < 0.05). L. paraplantarum KM was the best in percent conversion of glucosides to corresponding aglycones, resulting in 100%, 90%, and 61% hydrolysis of genistin, daidzin, and glycitin, respectively, in 6 h. Consequently, the aglycone concentrations in soymilk fermented with L. paraplantarum KM were 6 and 7-fold higher than the initial levels of daidzein and genistein, respectively, after 6 h of fermentation. Changes in the daidzin and genistin levels were not significant in soymilk fermented with E. durans KH. The rates of hydrolysis of glucosides varied depending on the species of LAB. Especially, L. paraplantarum KM seems to be a promising starter for bioactive-fermented soymilk based on its growth, acid production, and isoflavone conversion within a short time.