Change in physicochemical properties, phytoestrogen content, and antioxidant activity during lactic acid fermentation of soy powder milk obtained from colored small soybean

Abstract

This study investigated the changes in physicochemical properties, total phenolic and phytoestrogen (isoflavone) contents, and antioxidant activity, including 2,2-diphenyl-1-picrydrazyl (DPPH) and 2,4,6-azinobis (3-ethyl-benzothiazoline- 6-sulfonic acid) (ABTS) radical activities and ferric reducing antioxidant power (FRAP), during the lactic acid fermentation of soy powder milk (SPM) with colored small soybean (CSS) by the potential probiotic Lactobacillus plantarum P1201. The pH decreased, while viable cell numbers and β-glucosidase activities gradually increased during lactic acid fermentation of SPM. The total isoflavone content of Pungsannamul soybean was higher than that of other CSS cultivars. The isoflavone glycoside (daidzin and genistin) contents decreased whereas, corresponding isoflavone aglycone (daidzein and genistein) content significantly increased during the fermentative processing. In particular, fermented SPM prepared from Pungsannamul soybean showed highest daidzein (87.37 μg/g) and genistein (51.29 μg/g) after fermentation for 60 h. Total phenolic contents (TPCs) of Dawon soybean was higher than that of other CSS cultivars. TPC also increased marginally from 1.44-2.92 mg/g (0 h) to 1.79-3.03 mg/g (60 h) during lactic acid fermentation of SPMs with CSS. Finally, fermented SPM extracts possessed potent DPPH and ABTS radical scavenging activities and FRAP effects with change from 28.7-40.6 to 90-95.3%, 25.1-42.3 to 51.4-82.8%, and 0.73-1.54 to 0.98-1.79 (OD593 nm), respectively in pre-and post-fermented samples. Therefore, fermented SPM might contribute to enhance the value of CSS. Copyright ? The Korean Society of Food Preservation. All rights reserved.