Bacterial Contamination of Ready-to-Eat Foods and Fresh Products in Retail Shops and Food Factories

Abstract

Raw vegetables cut for salad, cooked salad, cooked rice, boiled noodles, bean curd, and cooked Japanese foods were purchased in 27 retail shops in Tokyo. Intact vegetables before being processed and ready-to-eat fresh salad products were obtained from two food factories located in the suburbs of Tokyo. Two hundred thirty-eight retail samples, 137 samples of intact vegetables, and 159 samples of fresh products were examined for aerobic plate count (APC), coliforms, Escherichia coli, Listeria spp., Staphylococcus aureus, and Bacillus cereus. The APC of retail foods were 2.1 to 5.7 log CFU/g, and the range for the coliforms was 0.1 to 2.3 log CFU/g. The APC and coliform values showed that the raw vegetables cut for salad were the most heavily contaminated among the six kinds of ready-to-eat foods examined. Although L. monocytogenes was not detected, two samples of raw vegetables and five kinds of cooked foods yielded Listeria spp. S. aureus was detected in one sample of Japanese cooked food. The APC of the intact vegetables were 2.9 to 7.3 log CFU/g upon arrival and 2.2 to 7.2 log CFU/g after 3 days storage at 10°C. The APC of the fresh products were 3.4 to 7.6 log CFU/g upon arrival and 4.7 to 8.7 log CFU/g after 3 days storage at 10°C. The isolation rates for coliforms were 6.1 to 50% for intact vegetables and 50 to 66.7% for fresh products. E. coli was detected only in the fresh products. B. cereus was isolated from 20.1% (17 of 81) of the intact vegetables and 9.2% (8 of 87) of the fresh products.