Microbiological Survey of Tofu Sold in a Rural Illinois County

Abstract

The purpose of this study was to determine the microbial status of tofu sold in a rural Illinois county and assess the factors contributing to the safety of tofu. Six brands of tofu from eight different stores (60 total samples) were purchased and analyzed for temperature, pH, total aerobic bacteria, and the presence of coliforms. Relationships between age, temperature, pH of tofu, and total aerobic bacteria were tested. An analysis of variance was also performed to test for differences in total bacterial counts among the brands. Mean aerobic bacterial counts ranged from 0 to 7.76 × 107 CFU/g. Fifty-five percent of the tofu tested fell within the excellent range for freshness as delineated by the standards developed by the Soyfoods Association of North America, 6.7% fell within the acceptable range, 6.7% within the marginal range, and 28% within the unacceptable range. Sixteen percent of the samples contained coliform bacteria. No significant correlation was found between variables, except pH with total aerobic bacterial counts (r = −0.51) and pH with eosin-methylene blue agar counts (r = −0.67). Most of the tofu was displayed at unsafe temperatures (>5°C) for potentially hazardous foods. This study confirmed the concerns regarding safety of tofu sold in the grocery stores. Based on these results, special training on tofu storage and handling is recommended for grocery stores selling this food product.