Antioxidant properties of polyphenol‐containing extract from soybean fermented with Saccharomyces cerevisiae

The antioxidant properties and total phenolic compounds of soybean extract fermented with Saccharomyces cerevisiae during 24 h were evaluated. Total polyphenolic compounds extracted in ethanol/water (1:1) solution were 789.54 mg/g dry extract, and flavonoids were 169.47 mg quercetin equivalents/g of dry extract. Reducing power (91.18%) and DPPH scavenging (79.30% at 4‐times diluted) were excellent, and so high as BHA, 92.17% and 73.8% respectively, while superoxide anion scavenging showed poor inhibition (4876 equivalent SOD U/g). Antioxidant activity in linoleic acid/water emulsion system of fermented extract measured as peroxide formation inhibition at 37 °C was the strongest (95.62%), while it exerted a moderate inhibition for conjugated dienes and thiobarbituric acid reactive substances (64.77% and 54.33%). At 80 °C the antioxidant activity assayed at a higher concentration was less effective (29.35% on CD; 74.58% on PV and 35.04% on TBARS).