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.