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, co oked delicatessen meats were identified as Lactobacillus sake, Lactoba cillus curvatus Lactobacillus sharpeae and Leuconostoc mesenreroides s sp. mesenteroides Lactobacillus spp. predominated and almost half of a ll 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 t o 98% lethality with 82 to 99.8% of survivors injured Lethality was gr eatest when thermal stress was applied to cells in phosphate buffer (p H 6.3), but the proportion of injured survivors present after heating in buffer or MRS broth did not differ. Repair of injury in lactobacill i was complete within 6 h in some trials at 34 degrees C, but at 4 deg rees C with Lactobacillus sake, > 10 days was required to achieve sign ificant repair Older cells were more resistant to thermal stress and w ere able to repair injury faster. The presence of catalase in the reco very medium facilitated repair by Lactobacillus sake. Lactobacillus cu rvatus was slightly less thermally-resistant but was also capable of r epairing induced injury. Lethality was severe (> 99.98 %) with the Leu conostoc 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