Studies On the Fluorescent Compound in Fermented Foods

Part IV. Degradation of added aflatoxin during miso fermentation

Abstract

As a basic experiment for the study of aflatoxin degradation during fermentation of miso, the effect of hydrogen-ion concentration to the degradation of aflatoxin was examined. It was found that the pH value for the most effectiVe degradation of aflatoxin was over 9 and contrary the most stable pH values for aflatoxin were 4-5. The pH values of 95 samples of the commercial miso from all of the prefectures in Japan were mostly between 4.6-5.4. As the result of this survey, it was shown that there was no effect of pH value of the miso as regard to aflatoxin degradation.
A certain amount of aflatoxin was added to green miso before fermentation in order to investigate the degradation of the toxin during miso fermentation. There was some degradation of aflatoxin B₁ and G₁ in miso in the early stage of the fermentation, but in the later the velocity was remarkably reduced. As the result, above 50 percent of aflatoxin B₁ and G₁ remained in miso after 1 month fermentation. With regard to aflatoxin B₂ and G₂, no degradation was detected during miso fermentation.