Effect of fermentation time on the antioxidant activities of tempeh prepared from fermented soybean using <i>Rhizopus oligosporus</i>

Abstract

Summary The objective of this study was to evaluate the effect of fermentation time on the antioxidant activity of tempeh, a fermented product from soybean. Rhizopus oligosporus was used to ferment soybean for 0, 1, 2, 5 and 10 days. Lyophilised tempeh powder was extracted with hexane followed by petroleum ether, ether, 95% ethanol and water. Antioxidant activities of the extracts were evaluated with various models including α,α‐diphenyl‐β‐pricryl‐hydrazyl (DPPH) and superoxide‐scavenging activities, reducing power and inhibitory activity towards lipid peroxidation. The results revealed that tempeh showed greater antioxidant activities than unfermented soybean. On behalf of a DPPH scavenger, water extracts were as good as 95% ethanol extracts. In comparison of superoxide anion‐scavenging activity, inhibition of lipid peroxidation and reducing power, 95% ethanol extracts were superior to water extracts. Tempeh fermented with R. oligosporus for 10 days exhibited the highest antioxidant activities than the others.