THE SURVIVAL AND GROWTH OF ACID-ADAPTED MESOPHILIC PATHOGENS THAT CONTAMINATE MEAT AFTER LACTIC-ACID DECONTAMINATION

Lactic acid decontamination (LAD) may adapt pathogens to lactic acid. Such organisms may have an increased resistance to acid and can contam inate meat after LAD, The survival and growth of acid adapted Campylob acter jejuni, Salmonella typhimurium. Escherichia coli O157 : H7 and S taphylococcus aureus inoculated on skin surface of still warm pork bel ly cuts 2 h after LAD was examined during chilled (4 degrees C) storag e and refrigeration abuse equivalent to 12.5 degrees C. Lactic acid de contamination included dipping in 1, 2 or 5% lactic acid solutions at 55 degrees C for 120 s. Lactic acid decontamination brought sharp redu ctions in meat surface pH, but these recovered with time after LAD at approximately 1-1.5 pH units below that of water-treated controls. A s harp decrease in the number of cfu of pathogens occurred on chilled 2- 5% lactic acid treated pork belly cuts when the skin surface was less than pH 4.8-5.2. The reductions ranged from 0.1-0.3 log(10) cfu cm(-2) for E. coli O157:H7 to over 1.7-2.4 log(10) cfu cm(-2) for Camp, jeju ni, respectively. Increase in storage temperature from 4 to 12.5 degre es C reduced delayed decrease in numbers of all pathogens except Camp. jejuni by a factor of two. Deaths in Camp, jejuni at 12.5 degrees C s lightly exceeded those at 4 degrees C, After the initial sharp decline , the number of cfu of mesophilic pathogens decreased gradually at a r ate similar to that on water-treated controls. Growth of all mesophili c pathogens except Camp. jejuni on 2-5% LAD meat occurred during stora ge at 12.5 degrees C when the meat surface pH exceeded 4.8-5.2, and wa s slower than on water-treated controls. Low temperature and acid-adap ted E, coli O157:H7, Salm. typhimurium and Staph. aureus, and acid ada pted Camp, jejuni that contaminate skin surface after hot 2-5% LAD, di d not cause an increased health hazard, although microbiota and intrin sic parameters (lactic acid content, pH) were created that could advan tage their survival and growth.