Isoflavone content and antioxidant activity of Thai fermented soybean and its capsule formulation

Soybeans (Glycine max) are usually eaten as processed foods. Fermented soybeans are among the most popular of these processed foods. The aim of this study was to determine the effect of fermentation duration on isoflavone content and antioxidant activity of fermented soybeans. Capsule formulation of fermented soybeans was also studied. The Thai soybean variety, Rajamangala60, was fermented with Aspergillus oryzae. Isoflavone content and antioxidant activity were studied at 0, 12, 18,36, 48, 96, 120, 168, 240, 360 and 480 h of fermentation duration. The results showed that isoflavone glycones (daidzin and genistin) decreased during fermentation, but aglycones (daidzein and genistein) increased. The highest amount of isoflavone aglycones was 384.30 ± 4.60 and 116.50 ± 1.56 mg/100 g fermented soybeans for daidzein and genistein, respectively. Antioxidant activity of fermented soybeans was evaluated by ABTS cation radical scavenging and ferric reducing antioxidant power(FRAP) methods. Antioxidant activity of fermented soybeans is increased during fermentation. Increases in isoflavone aglycones content and antioxidant activity were related to fermentation duration. The highest antioxidant activity of fermented soybean was found at the 240 h of fermentation with trolox equivalent antioxidant capacity (TEAC) 1.98 ± 0.09 ìg trolox/g fermented soybean and FRAP value of 0.623 ± 0.002 g FeSO4/g fermented soybean. Soybeans fermented for 240 h were thenformulated as capsules by a wet granulation method. They were then assessed for appearance, weight variation, disintegration time and antioxidative properties. The results showed that fermented soybeancapsules conformed to USP32/NF27 criteria on weight variation and disintegration. Their antioxidant activity was lower than 240 h fermented soybeans, but still higher than the non-fermented ones (p <0.05)

Functional properties of β-glucosidase-producing Lactobacillus plantarum SC 359 isolated from Thai fermented soybean food

The aims of this study were to isolate LAB from Thai plant-derived foods and beverages and to examine in vitro probiotic properties including b-glucosidase enzyme activity. Lactobacillus plantarum SC 359 selected from Thai pickled soybean was significantly (P−1 at 18 h of incubation) out of the 227 tested strains. The strain survived in 0.30% (w/v) bile salt and had high tolerance to acidic pH with survival rates at a 2 h period of 72.24%, 85.52%, 92.64%, and 93.38% at pH 2.0, 3.0, 4.0, and 5.0, respectively. The SC 359 strain showed proteolytic and lipolytic activities. Moreover, the selected strain displayed strong antagonistic activities against Bacillus cereus ATCC 11778, Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa ATCC 27853, Salmonella Typhi, Shigella sonnei and Candida albicans ATCC 90028. The strain was susceptible to ampicillin, chloramphenicol, erythromycin, gentamicin, kanamycin, rifampicin, streptomycin, tetracycline, and vancomycin. In addition, the selected strain significantly inhibited the adherence to Caco-2 cells of E. coli, S. Typhi and Sh. sonnei (P<0.05) by 33.50 to 73.37%. The strain could obstruct the adherences of pathogens by elimination, competition, and displacement with pathogen adherences 33.62–53.92%, 26.63–59.23%, and 49.41–66.50%, respectively. Based on the results, the selected strain could be applied as functional starter for Thai fermented plant-derived foods and beverages