Immediate and Delayed Microbiological Effects of Lactic Acid Decontamination of Calf Carcasses - Influence on Conventionally Boned Versus Hot-Boned and Vacuum-Packaged Cuts

Abstract

Three experiments involving a total of 114 calves were done. The first two experiments, conducted under simulated export conditions, monitored the immediate and delayed microbiological effects of decontamination with 1.25% (vol/vol) L-lactic acid on calf carcasses as well as the effects of an additional treatment with 2.00% (vol/vol) L-lactic acid and vacuum-packaging on hot-boned veal cuts. In a third experiment, data from these investigations were tested under actual export conditions and were found to be similar. As a result of 1.25% (vol/vol) L-lactic acid treatment, aerobic colony counts (3 d at 30°C and 5 d at 17°C) were reduced by 0.8 log10 CFU as compared with initial counts of approximately 3.0 log10 CFU/cm2 on control carcasses. However, the reduction increased to 1.3 log10 CFU at 14 d postmortem, indicating some delayed effect of lactic acid. The percentage of samples positive for Enterobacteriaceae was reduced from 50% to approximately 10% which corresponded with a mean reduction of 0.3 log10 CFU/cm2. Vacuum-packaging virtually completely inhibited growth of bacteria, yeasts and molds on hot-boned cuts, but 1 wk after breaking the counts reached values similar to controls. When measured 7 d postmortem, lactic acid treatment combined with vacuum-packaging was significantly more effective in reducing aerobic colony counts than vacuum-packaging alone. At 14 d postmortem, this was still the case for cuts that had been subjected to an additional decontamination with 2.00% (vol/vol) L-lactic acid immediately before vacuum-packaging. The Enterobacteriaceae colony count of hot-boned vacuum-packaged cuts remained under its limit of detection of 1.3 log10 CFU as a result of lactic acid decontamination. Lactobacillaceae colony counts were extremely low in all treatment groups. No salmonellae were isolated from any sample, indicating that marked progress has been made in controlling Salmonella contamination of veal in The Netherlands. This was accomplished by having separate fattening and slaughter lines and markedly improving slaughter house practices.