Storage effects on the content of anthocyanin, mutagenicity and antimutagenicity of black soybean koji

Black soybean koji, possessing antimutagenicity, has been suggested as a potential ingredient for the preparation of healthy food. The objective of this research was to determine the potential mutagenicity and the changes of antimutagenicity of the extract of Aspergillus awamori-fermented black soybeans (koji) held at 4 and 25 °C with or without deoxidant and desiccant for a period of 120 days. It was found that no mutagenic compound formed during the storage period. Depending upon storage temperature and packaging condition, the antimutagenicity of the extract of koji reduced and was associated with a reduction in anthocyanin content during the storage period. Generally, koji stored at 4 °C with both deoxidant and desiccant retained the highest antimutagenicity among the various storage conditions examined. At the end of storage, the extract of black soybean stored at 4 °C with both deoxidant and desiccant retained 79.74 and 87.80% of its original antimutagenicity against 4-nitroquinoline-N-oxide in Salmonella Typhimurium TA98 and TA100, respectively. An extract of black soybean koji stored under similar storage condition showed an antimugenicity residual of 88.23 and 79.34% against benzo[a]pyrene in S. Typhimurium TA98 and TA100, respectively.