Antioxidative Activity of Douchi (A Chinese Traditional Salt-Fermented Soybean Food) Extracts During Its Processing

Abstract

Salt-fermented soybean foods are popular in Asia as an alternative food seasoning material. The α,α-Diphenyl-β-pricrylhydrazyl (DPPH) radical-scavenging activity, 2,2′-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical-scavenging activity and reducing power of the 50% ethanol extracts from one variety called in layman term as douchi were evaluated in this study. TEAC on DPPH radical and ABTS radical of extracts and the reducing powers of the extracts was found to increase significantly during the prefermentation (p < 0.05), through to the postfermentation. We investigated the effect of adding salt to the antioxidative activity during postfermentation. It was found that high salt content was not favorable for high TEAC on DPPH radical and the reducing powers. The effect of salt content on TEAC on ABTS radical of extracts was not significant (p > 0.05). The results showed that the antioxidative compounds released during the douchi fermentation were inhibited by the high salt addition.

Keywords:

• Douchi
• Antioxidative activity
• DPPH
• ABTS
• Reducing power

ACKNOWLEDGMENTS

This study was conducted within the framework of the collaborative research project between Japan and China titled, “Development of sustainable production and utilization of major food resources in China,” supported by Japan International Research Center for Agricultural Sciences (JIRCAS). This work was supported using the fund (DIC2003-04) called, “Study on the antioxidative activities of the Chinese traditional fermented soybean foods,” from the Research/Communication Proposal of Danone Institute China.