Over a period of 4 years, 770 low-acid canned food spoilage incidents were investigated to determine the cause of spoilage. In 27 of these, the cause was attributed to the growth of bacteria of the Clostridium genus that had entered the cans as a result of post-processing leakage. No correlations were found that might explain the occurrence of this mesophilic anaerobic type of spoilage. It appears to be a random event, probably linked to cannery insanitation. A variety of species was found, consisting of both proteolytic and non-proteolytic types. Clostridium botulinum was not isolated from any of the canned foods examined, nor were any of the samples found to contain botulinal toxin. Container leak test methodology and principles are discussed.

I Fifty-nine samples of can-cooling water from 30 midwestern canneries were examined for aerobic plate count, salmonellae, coagulase-positive staphylococci, coliforms, enterococci, and mesophilic aerobic and anaerobic (putrefactive) spores including spores of Clostridium botulinum. No Salmonella or C. botulinurn were detected. Indicator bacteria counts were low with nearly 75% of the samples showing MPN levels of

Microbiological surveys of post-processing can handling equipment were conducted in three low-acid food canneries to identify the source and numbers of mesophilic anaerobic sporeformers isolated from post-processing spoilage of cans packed at those canneries. Significant numbers of spores of these organisms were found on various equipment and can tracks. The spores were also isolated from the can cooling waters in two of the canneries and in numbers higher than have been reported previously. No correlation was noted between mesophilic anaerobic spore counts and total aerobic counts in samples obtained from the surveys. Clostridium botulinum was not isolated from any of the survey samples. A medium useful in the isolation of mesophilic anaerobic sporeformers is described.