Hee Yul Lee

Potential Probiotic Lactobacillus plantarum P1201 to Produce Soy-yogurt with Enhanced Antioxidant Activity

In this study, we evaluated changes in physicochemical properties, total phenol and isoflavone contents, and antioxidant activity during soymilk fermentation by a potential probiotic Lactobacillus plantarum P1201. The P1201 strain showed survival rates of 58.14% and 62.22% after 4 h exposure to acid and artificial gastric acid conditions (pH 2.5), respectively. The optimal conditions for soy-yogurt fermentation by L. plantarum were determined to be as follows: temperature of 35oC, seed volume of 5.0%, and sucrose content of 10.0%. The total phenol and isoflavone contents and antioxidant activity were higher in soy-powder milk (SPM) yogurt than soymilk yogurt. In particular, the highest levels of isoflavone-aglycones, such as daidzein, glycitein, and genistein (91.50, 12.34, and 61.39 μg/g, respectively), were observed after 48 h of SPM fermentation. Thus, these results suggest that the soy-yogurt extract could be used as a potential source of natural antioxidants in food. Kewwords: probiotic, Lactobacillus plantarum P1201, soy-yogurt, antioxidant, isoflavone

Effects of roasting on the phytochemical contents and antioxidant activities of Korean soybean (Glycine max L. Merrill) cultivars

Antioxidant activities of roasted soybeans from Daewon, Daepung, Neulchan, and Taekwang cultivars were evaluated using DPPH and ABTS radical scavenging activities and FRAP assays. Roasted soybeans exhibited significantly (p<0.05) higher antioxidant activities than unroasted soybeans. Daepung soybeans roasted at 200°C for 15 min exhibited higher antioxidant activities than other cultivars and soybeans roasted under other conditions. Contents of antioxidant compounds, including isoflavone aglycones, glycosides, and phenolic acids, increased after roasting, whereas the content of isoflavone malonlyglycosides was decreased in the roasted soybeans. Moreover, total phenolic and flavonoid contents and isoflavone aglycone, glycoside, and phenolic acid contents were increased, leading to a general increase in antioxidant activities due to roasting.

Comparison of Isoflavone Contents and Antioxidant Effect in Cheonggukjang with Black Soybean Cultivars by Bacillus subtilis CSY191

BACKGROUND: Soybeans are the rich sources of isoflavones. To date, the changes of isoflavone contents in various black soybeans cheonggukjang during fermentation by Bacillus subtilis CSY191 has not been investigated.METHODS AND RESULTS: This study investigated the changes of total phenolic and isoflavone contents and antioxidant effects during cheonggukjang fermentation made with four black soybean (BS) cultivars including Cheongja, Cheongja#3, Geomjeong#5, and Ilpumgeomjeong with a potential probiotic Bacillus subtilis CSY191. The total phenolic contents, isoflavone-malonylglycoside and -aglycone contents, and antioxidant activity were increased in cheonggukjang at 48 h fermentation, while the content of isoflavone-glycosides was decreased during cheonggukjang fermentation. In particular, the Cheongja#3 soybean fermented at 37℃ for 48 h displayed the highest antioxidant activities, compared to those of the other BS cultivars tested. Also, the highest levels of total phenolic, daidzein, glycitein, and genistein were present at concentrations of 17.28 mg/g, 283.7 g/g, 39.9 g/g, and 13.2 g/g at the end of Cheongja#3 soybean fermentation.CONCLUSION: The results from this study suggested that the enhanced antioxidant activity of cheonggukjang of BS might be related to increased levels of total phenolic, isoflavon-aglycone, and malonyl-glycoside contents achieved during fermentation. Furthermore, fermented Cheongja#3 soybean showed the highest levels of enhanced antioxidant activities than the other BS cultivars.