Effects of Ripening Process on the Mutagenicity and Antimutagenicity of Sufu, a Chinese Traditional Fermented Product of Soybean

摘要

In the present study, sufu, the cheese-like fermented product of soybean, was prepared by ripening salted tofu cubes in Aspergillus oryzae-fermented rice–soybean koji mash at 35 °C for a period of 16 days. This mixture was held at room temperature (ca. 25 °C) for another 1 month. The mutagenicity and antimutagenicity exerted by the methanol extract of non-fermented tofu and sufu against 4-nitroquinoline N-oxide (4-NQO), a direct mutagen, and 3, 2-dimethyl-4-amino-biphenyl hydrochloride (DMAB), an indirect mutagen, on Salmonella typhimurium TA 100 were examined. Results revealed that the methanol extract of non-fermented tofu and sufu samples collected at various ripening intervals exhibited neither toxicity nor mutagenicity, yet did display antimutagenicity against mutagens across the dose levels examined. Generally, a dose-dependent antimutagenic effect was noted across the dose range examined. The antimutagenicity of the tofu extract toward 4-NQO and DMAB was enhanced significantly (P 0.05) through fermentation. Generally, the antimutagenicity of the sufu extract increased with the extension of ripening period. Furthermore, the extract of the non-fermented tofu and sufu, regardless of ripening period, showed a significantly higher (P 0.05) antimutagenicity against DMAB than 4-NQO.