title: Fate of low temperature and acid-adapted Yersinia enterocolitica and Listeria monocytogenes that contaminate lactic acid decontaminated meat during chill storage.
abstract: 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 equal to 1-1.5 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 the growth of acid-adapted organisms.
authors.affiliation: Department of Food of Animal Origin, School of Veterinary Medicine, Utrecht University, The Netherlands.
authors.forename: P
authors.initials: P
authors.lastname: van Netten
authors.forename: A
authors.initials: A
authors.lastname: Valentijn
authors.forename: D A
authors.initials: DA
authors.lastname: Mossel
authors.forename: J H
authors.initials: JH
authors.lastname: Huis in 't Veld
mesh_terms: D004352:Drug Resistance, Microbial; D005506:Food Contamination / Q000517:prevention & control*; D005516:Food Microbiology; D005524:Food Technology; D019344:Lactic Acid / Q000008:administration & dosage*; D008089:Listeria monocytogenes / Q000187:drug effects*; D008460:Meat / Q000382:microbiology*; D008826:Microbial Sensitivity Tests; D015008:Yersinia enterocolitica / Q000187:drug effects*
chemical_list: D019344:Lactic Acid