Fate of Enteropathogens Inoculated onto Chopped Ham ¹

A survey of 36 pairs of new (< 10 days from manufacture) and old (pull date) samples of vacuum-packaged, sliced chopped ham were analyzed for total microbial load, specific pathogen count and pH. Results indicated a wide range of microbial loads, absence of pathogenic bacteria at the levels tested, and presumptive group D streptococci generally < 100/g except for 22% of new samples and 44% of old samples, which had presumptive group D counts > 100 but < 10⁶/g. The survey results also indicated marked differences in pH between products from different manufacturers. Product from two manufacturers was selected for inoculation studies. Chopped ham sandwiches were inoculated with a mixture of five enteropathogenic bacteria and held at 30, 21 and 4 C for up to 24 h. Bacillus cereus , Escherichia coli , Salmonella typhimurium and Staphylococcus aureus , but not Clostridium petfringens , grew in low competition product under the severely abusive holding temperature of 30 C in < 24 h, at 21 C in > 24 h. Product from one manufacturer inhibited the gram negative pathogens. Results indicated that chopped ham in sandwiches required almost unrealistic mishandling to develop a food poisoning potential by enterotoxigenic bacteria, but infective pathogens survived well.