Lactic acid as a decontaminant in slaughter and processing procedures

Abstract

An attempt was made to interrelate the data obtained in experiments conducted by our Department along beef veal and pig slaughter lines, using lactic acid (LA) for the decontamination of carcasses, cold and hot boned primal cuts, slaughter byproducts, and butchers’ knives. First and foremost it was observed, that provided Good Manufacturing Practices are strictly followed, the microbial load of carcass surfaces will be substantially reduced. LA‐decontamination may result in an additional reduction. Since in the early post‐mortem period bacteria are not yet attached to the meat surface, LA‐decontamination should preferably be applied to the hot carcass. It was demonstrated that, dependent on mode and duration of application, LA sprays not exceeding 1% v/v (beef), 1.25% v/v (veal) and 1.5% v/v (pork) resulted in acceptable carcass colour scores. Blood spots, which are particularly prone to discolouration by lactic acid application, should be removed at an early postmortem stage e.g. by strong showering. The difference in surface pH between LA‐treated and control carcasses disappeared within 72 hours post‐mortem. Veal longissimus chops treated with LA solutions up to 2% v/v were not identified by a consumer tastepanel as significantly different from controls. The ‘immediate’ bactericidal effect of LA‐decontamination for beef veal and pig carcasses, as well as for pig liver and veal brain, amounted to approximately 1.5 log cycles for the aerobic colony counts, strongly dependent on substrate and conditions of decontamination. In addition, a ‘delayed’ bacteriostatic effect was observed during storage, which is probably the result of a prolonged lag phase of acid‐injured micro‐organisms surviving lactic acid decontamination. Ecological surveys revealed that LA resulted in a shift towards a Gram positive bacterial association acting as an antagonist of enteropathogenic Gram negative bacteria. Electrostatic application of LA solutions may contribute to limiting the amount of LA needed for effective decontamination. Adding 2.7% v/v LA to the spray water of a specially designed disinfection unit for butchers’ knives effected a reduction in aerobic colony counts at 45° C which exceeded that achieved by conventional sanitizers at 82° C.