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 as Lactobacillus sake, Lactobacillus curvatus Lactobacillus sharpeae and Leuconostoc mesenreroides ssp. mesenteroides Lactobacillus spp. predominated and almost half of all isolates were L sake. Treatment of Lactobacillus sake at 53 degrees C to 55 degrees C for less than or equal to 12 min yielded front 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 degrees C, but at 4 degrees C with Lactobacillus sake, > 10 days 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 by Lactobacillus sake. Lactobacillus curvatus was slightly less thermally-resistant but was also capable of repairing induced injury. Lethality was severe (> 99.98 %) with the Leuconostoc spp. tested at 53 degrees C for 8 min. Repairable injury was not demonstrated in the latter organisms following this treatment. (C) 1996 Academic Press Limited