Isoflavone phytoestrogen degradation in fermented soymilk with selected β-glucosidase producing L. acidophilus strains during storage at different temperatures

• Published in: International journal of food microbiology Vol. 115; no. 1; pp. 79 - 88
• Main Authors: Otieno, D.O., Ashton, J.F., Shah, N.P.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-04-2007
• Subjects: beta-Glucosidase - metabolism; Bioactive; bioactive properties; biodegradation; bioprocessing; Biotransformation; Chromatography, High Pressure Liquid - methods; daidzein; Degradation kinetics; Fermentation; Food Handling - methods; Food Microbiology; Food Preservation - methods; food storage; genistein; glycitein; Isoflavones; Isoflavones - analysis; Isoflavones - metabolism; isolation; Kinetics; lactic acid bacteria; Lactobacillus acidophilus; Lactobacillus acidophilus - enzymology; Soy Milk - chemistry; soymilk; Stability; starter cultures; storage temperature; Temperature; Time Factors; Stability; Degradation kinetics; Lactobacillus acidophilus; Bioactive; Biotransformation; Isoflavones
• ISSN: 0168-1605; 1879-3460
• DOI: 10.1016/j.ijfoodmicro.2006.10.028

Soymilk fermented with 3 selected
Lactobacillus acidophilus strains were stored at various temperatures (−
80 °C, 4 °C, 25 °C and 37 °C) for 8 weeks and the concentration of isoflavones determined weekly using RP-HPLC. The decreasing concentration of isoflavones in soymilk during storage due to degradation was found to fit the first order kinetics model. Isoflavone aglycones as well as isoflavone glucosides largely appeared to be stable during storage (
P
<
0.01). Interestingly, the aglycone forms showed much smaller degradation as compared to glucoside forms at all the storage temperatures studied. Of the isoflavone aglycones, daidzein was found to be the most stable followed by genistein, while glycitein was least stable. Isoflavone aglycones such as glycitein, daidzein and genistein showed smaller degradation constants in fermented soymilk at lower storage temperatures (−
80 °C and 4 °C) and higher degradation constants at higher storage temperatures (25 °C and 37 °C) with each strain. In contrast, glucosides glycitin and daidzin showed higher degradation at lower storage temperatures (−
80 °C and 4 °C) and lower degradation at higher storage temperatures (25 °C and 37 °C). Storage temperature was therefore found to be very important in regulating the rate of degradation soy isoflavones in fermented soymilk.