Incidence of Clostridia in Cooked Meat Products in Japan

A total of 469 cooked meat products collected from meat processing factories in Tokyo were examined for contamination by Clostridium species. Enumeration of Clostridia was made by the MPN method with H2S production as an indicator. The Clostridia were detected in 154 (32.8%) products, with more than half of the sausages indicating contamination. One hundred forty (90.9%) of the positive samples showed contamination of less than 10 of the organisms/g. A total of 15 species, such as Clostridium bifermentans, Clostridium perfringens and Clostridium sporogenes were identified. Clostridium botulinum was not detected. One hundred sixty-seven (75.9%) strains of the spores of 220 typical isolates survived heat treatment of 65°C for 30 min, whereas only 15 (6.8%) remained intact at 100°C for 10 min. Growth which was noted in most species at 10°C was rarely detected at 5°C. Although 165 (75.0%) of these strains demonstrated proteolytic activity, lipolytic activity was hardly seen except in C. sporogenes. The results suggest that presence of the Clostridia should not be ignored in assessment of the bacteriological quality of the cooked meat products, especially of sausages.