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Fate of low temperature and acid-adapted Yersinia enterocolitica and Listeria monocytogenes that contaminate lactic acid decontaminated meat during chill storage
- Netten, P. van, Valentijn, A., Mossel, D.A.A., Huis in 't Veld, J.H.J.
- Journal of applied microbiology 1997 v.82 no.6 pp. 769-779
- Listeria monocytogenes, Yersinia enterocolitica, acid tolerance, cold storage, decontamination, dipping, health hazards, lactic acid, pH, parents, pathogens, pork bellies, slaughterhouses, spoilage, temperature
- Pathogens found in the environment of abattoirs may become adapted to lactic acid used to decontaminate meat. Such organisms are more acid tolerant than non-adapted parents and can contaminate meat after lactic acid decontamination (LAD). The fate of acid-adapted Yersinia enterocolitica and Listeria monocytogenes, inoculated on skin surface of pork bellies 2 h after LAD, was examined during chilled storage. LAD included dipping in 1%, 2% or 5% lactic acid solutions at 55 degrees C for 120 s. LAD brought about sharp reductions in meat surface pH, but these recovered with time after LAD at approximately 1.5 pH units below that of water-treated controls, growth permitting pH at 4.8-5.2 was reached after 1% LAD in less than 0.5 d (pH 4.8-5.0), 2% LAD within 1.5 d (pH 4.9-5.1) and after 5% LAD (pH 5.0-5.2) within 4 d. During the lag on 2% LAD meat Y. enterocolitica counts decreased by 0.9 log10 cfu per cm2 and on 5% LAD the reduction was more than 1.4 log10 cfu per cm2. The reductions in L. monocytogenes were about a third of those in Y. enterocolitica. On 1% LAD the counts of both pathogens did not decrease significantly. The generation times of Y. enterocolitica and L. monocytogenes on 2.5% LAD meats were by up to twofold longer than on water-treated controls and on 1% LAD-treated meat they were similar to those on water-treated controls. Low temperature and acid-adapted L. monocytogenes and Y. enterocolitica that contaminate skin surface after hot 2-5% LAD did not cause an increased health hazard, although the number of Gram-negative spoilage organisms were drastically reduced by hot 2-5% LAD and intrinsic (lactic acid content, pH) conditions were created that may benefit the survival and growth of acid-adapted organisms.