Mutagenic Analysis of Fermenting Strains and Fermented Brine for Stinky Tofu

Stinky tofu, a popular fermented food in Taiwan and South China. is conventionally made by open-type natural fermentation in which the product quality is not easily controlled. The Food Industry Research and Development Institute (FIRDI) in Taiwan has attempted to isolate the major fermenting strains from stinky brine in order to produce stinky tofu that is sanitary and ensure its quality. This study investigated the mutagenicities of isolated fermenting strains and their fermented brine for stinky tofu by two assays: (I) Ames rest and (II) mutation assay with human lymphoblast TK6 cells. In the Ames test, the number of revertants of Salmonella typhimurium TA98 and TA 100 was at the same levels under the dose of fermenting strain lysates (10(7) cfu/ plate) and 10-fold dilution of the fermented brine compared with the respective control. In the mutation assay with TK6 cells, the same samples were tested and the mutant frequencies were comparable to the respective control. Experimental results provided no evidence of mutagenic activity attributed to the tested materials.