Changes in the radical scavenging activity of bacterial-type douchi, a traditional fermented soybean product, during the primary fermentation process.

We studied the effects of isoflavones and peptides on antioxidant activities of bacterial-type douchi during fermentation. Radical scavenging activities increased with increasing fermentation time. Isoflavone conversion was not obvious, while soy protein hydrolyzed dramatically during fermentation. These results suggest that soybean peptides rather than isoflavones result in variations in antioxidant activity in bacterial-type douchi.