Identification of Lactic Spoilage Bacteria from Vacuum-packed Cooked Luncheon Meat and Induction of Repairable Injury By Mild Thermal Stress

Spoilage organisms isolated from retail samples of vacuum-packaged, cooked delicatessen meats were identified asLactobacillus sake,Lactobacillus curvatus,Lactobacillus sharpeaeandLeuconostoc mesenteroidesssp.mesenteroides.Lactobacillusspp. predominated and almost half of all isolates wereL sake. Treatment ofLactobacillus sakeat 53 °C to 55 °C for ≤ 12 min yielded from 15 to 98% lethality, with 82 to 99.8% of survivors injured. Lethality was greatest when thermal stress was applied to cells in phosphate buffer (pH 6.3), but the proportion of injured survivors present after heating in buffer or MRS broth did not differ. Repair of injury in lactobacilli was complete within 6 h in some trials at 34 °C, but at 4 °C withLactobacillus sake, > 10 d was required to achieve significant repair. Older cells were more resistant to thermal stress and were able to repair injury faster. The presence of catalase in the recovery medium facilitated repair byLactobacillus sake.Lactobacillus curvatuswas slightly less thermally-resistant but was also capable of repairing induced injury. Lethality was severe (>99.98 %) with theLeuconostocspp. tested at 53 °C for 8 min. Repairable injury was not demonstrated in the latter organisms following this treatment.