Factors Affecting the Safety of Canned, Cured, Shelf-stable Luncheon Meat Inoculated with Clostridium botulinum

Abstract

Ground pork was inoculated with spores of Clostridium botulinum types A and B and thermally processed. Factors which affected toxinogenesis were the number of spores, the concentrations of sodium chloride (salt) and sodium nitrite, and the amount of thermal processing. Meat inoculated with 1 spore per g and processed to Fo = 0.6 became toxic if salt and nitrite were omitted. In contrast, meat inoculated with 106 spores per g remained non-toxic after the same thermal process provided sufficient salt and nitrite were present, i.e., with a brine (% salt in the aqueous phase) of 6.1% and no added nitrite, with a brine of 4.6% and 300ppm of added nitrite, or with intermediate concentrations of salt and nitrite.The amount of thermal processing required to prevent toxinogenesis in meat with 146ppm of nitrite and 5.5% brine depended on the concentration of spores. An Fo of 0.15 did not prevent toxinogenesis in meat inoculated with 104 spores per g; an Fo of 0.3 prevented toxinogenesis with 104, but not with 106 spores per g; and an Fo of 0.6 prevented toxinogenesis in meat inoculated with 106 spores per g. However, when the brine was decreased to 4.8%, meat with 146ppm of nitrite and 106 spores per g became toxic even after an Fo of 0.68.Viable spores of C. botulinum were recovered 18 months after processing although the meat remained non-toxic, and normal in appearance and odour during this period.It is probable that some shelf-stable cured meats are safe because of the scarcity of C. botulinum in the raw product.