Modelling temperature variability in batch retorts and its impact on lethality distribution

Experimental time-temperature distributions From two different industrial s cale retort systems were statistically analysed. The retort temperature was modelled as the sum of a trend value and a residual, with the trend temper atures being simple functions of time. The residuals were modelled using ti me-series. The resulting impact on the lethality distribution was assessed by calculating the F-value distribution in the centre of cans simulated via a conduction-heating finite element model for 180 simulated temperature hi stories. Comparing the distributions obtained with those calculated using t he actual experimental temperature histories validated the applicability of this approach. The results indicated that the experimental and the modelle d average lethalities were statistically similar at 95% confidence. The sta ndard deviation was also similar for the F-value up to the end of holding b ut larger for the modelled distribution when considering the whole cycle, w hich was attributed to a correlation between the heating and cooling parame ters that was not considered in the model. (C) 2000 Published by Elsevier S cience Ltd. All rights reserved.