Reduction of aflatoxins and ochratoxin A by addition of commercial Koji during fermentation of the Korean traditional soybean paste, Doenjang

Contamination by aflatoxins and ochratoxin A of traditional Korean fermented soybean paste (Doenjang) is a serious food safety issue. In this study, we investigated the inhibitory effects of commercial Koji, a microbial starter culture used for fermentation, on mycotoxin contamination during Doenjang production at in vitro and scaled-up fermentation levels. A commercial Koji dominated by Aspergillus oryzae JI-4 exhibited strong antifungal and antimycotoxigenic activities against aflatoxigenic Aspergillus flavus and ochratoxigenic Penicillium verrucosum both in vitro and in situ. Furthermore, co-inoculation with Koji JI and mycotoxigenic fungi in the early stage of Doenjang fermentation significantly suppressed aflatoxins and ochratoxin A production by more than 93% (p < 0.05) and improved the nutritional properties and sensory qualities of the final product. These results suggest that the addition of commercial Koji could be an effective and practical approach to reduce aflatoxins and ochratoxin A contamination during the fermentation of soybean paste.