Lethality of heat to Escherichia coli O157 : H7: D- and z-value determinations in turkey, lamb and pork

Thermal inactivation of a four-strain mixture of E. coli O157:H7 was determ ined in lean ground turkey, lamb and pork. Inoculated meat was packaged in bags completely immersed in a circulating water bath and held at 55, 57.5, 60, 62.5, and 65 degrees C for predetermined lengths of time. The surviving cell population was enumerated by spiral plating meat samples on tryptic s oy agar overlaid with Sorbitol MacConkey agar. D-values, determined by line ar regression, in turkey were 11.51, 3.59, 1.89, 0.81 and 0.29 min at 55, 5 7.5, 60, 62.5 and 65 degrees C, respectively (z = 6.5 degrees C). When a su rvival model was fitted to the non-linear survival curves, D-values in turk ey ranged from 11.26 min at 55 degrees C to 0.23 min at 65 degrees C (z = 6 degrees C). When the E. coli O157:H7 four-strain cocktail was heated in gr ound pork or lamb, D-values calculated by both approaches were similar at a ll temperatures. Thermal-death-times from this study will assist the retail food industry to design cooking regimes that ensure safety of ground muscl e foods contaminated with E. coli O157:H7. Published by Elsevier Science Lt d. on behalf of the Canadian Institute of Food Science and Technology. All rights reserved.