MODEL OF THE INFLUENCE OF TIME AND MILD TEMPERATURE ON LISTERIA-MONOCYTOGENES NONLINEAR SURVIVAL CURVES

Heat treatment has long been regarded as one of the most widely used a nd most effective means of destroying pathogens in food. Up to now the linear relationship between the death rate and the temperature has be en used when choosing the best hear treatment to apply. However, the i nformation given by this linear relationship is no longer sufficient w hen nonlinear survival curves are observed. Consequently, the agri-foo d industry needs a tool to choose the best mild heat treatment to appl y in the case of nonlinear survival curves. This study deals with the temperature-induced death of Listeria monocytogenes CIP 7831 in the st ationary phase of growth. Eleven temperatures were tested. With the pr oposed primary and secondary models good fits of our data were obtaine d. A model describing both the effect of the duration of treatment and the temperature on the logarithm of the number of survivors was then built. A clear increase in the precision of the estimation of the para meters was obtained with this model. Moreover, with this model a new g raphical strategy to choose a mild heat increase regarding a maximal s urvivor number has been proposed. (C) 1998 Elsevier Science B.V.