Thermal inactivation of Yersinia enterocolitica in pork slaughter plant scald tank water

The objective of this study was to establish the time-temperature combination S required to ensure the thermal inactivation of Yersinia enterocolitica during scalding of pork carcasses. A 2 strain cocktail of Y. enterocolitica (bioserotypes 2/O:5,27 and 1A/O:6,30) was heat treated at 50, 55 and 60 degrees C in samples of scald tank water obtained from a commercial pork slaughter plant. Samples were removed at regular intervals and surviving cells enumerated using (i) Cefsulodin-Irgasan-Novobiocin Agar (CIN) supplemented with ampicillin and arabinose and (ii) Tryptone Soya Agar (TSA), overlaid with CIN agar with ampicillin and arabinose. The data generated was used to estimate D- and z-values and the formula D-x = log(-1) (log D-60 -((t(2) - t(1))/z)) was applied to calculate thermal death time-temperature combinations from 55 to 65 degrees C. D-50, D-55 and D-60-values of 45.9, 10.6 and 2.7 min were calculated from the cell counts obtained on CIN agar, respectively. The corresponding D-values calculated from the TSA/CIN counts were 45.1, 11 and 25 min, respectively. The z-value was 7.8. It was concluded that a time-temperature combination of 2.7 min at 60 degrees C is required to achieve a 1 log reduction in Y. enterocolitica in pork scald tank water. The predicted equivalent at 65 degrees C was 0.6 min. This study provides data and a model to enable pork processors to identify and apply parameters to limit the risk of carcass cross-contamination with Y. enterocolitica in pork carcass scald tanks. (C) 2012 Elsevier Ltd. All rights reserved.