Heat resistance of coliform species isolated from cooked ham, snail flesh, and 'bouchees a la reine'

Abstract

In this study, the heat resistance of coliform species isolated from cooked ham and ready-made meals was determined. Thirteen coliform strains belonging to 12 different species were studied using laboratory medium in order to determine delta (first decimal reduction time) and z(T) values (temperature increase leading to a 10-fold reduction of delta) using the Weibull model. For seven strains, delta-values were determined at temperatures ranging from 55 to 60 degrees C, with, delta values between 0.52 and 2.98 min, at 59 degrees C. For the other six strains, lower temperature values were determined with delta-values ranging from 0.47 to 1.64 min at 54 degrees C. z(T) values calculated for the 13 strains were 3.1 to 7.5 degrees C. For eight strains, plotting of the log of survivors was not linear but rather showed shoulders or shoulders and tails. Coliform species were sensitive to heat treatment with a decimal reduction time under 2 min at 60 degrees C. The better knowledge of coliform heat resistance by determining thermal resistance parameters with confidence intervals will be useful for evaluating the efficiency of industrial thermal processes.