A cardinal model to describe the effect of water activity on the growth ofmoulds

A simple model was proposed to describe the effect of water activity (Aw) o n the radial growth rate of moulds. This model is deduced from the cardinal model family proposed by Rosso in 1995, which is only defined from cardina l values of environmental factors (minimum, optimum and maximum values), th e growth rate observed at the optimal value of the environmental factors, a nd n, a shape parameter. For Aw, a simple form of cardinal model is propose d. This form is obtained for n = 2 and Aw(max) = 1.0 (pure water). The fina l model is so defined from only three parameters: Aw(min), Aw(opt), and opt imal radial growth rate (RGR(opt)). This model was successfully fitted on a data set of Aspergillus flavus, Aspergillus nomius, Aspergillus oryzae, As pergillus parasiticus, Aspergillus candidus, Aspergillus sydowii, Eurotium amstelodami, Eurotium chevalieri, and Xeromyces bisporus. The same quality of fit was obtained for different solutes used to control the Aw (NaCl, glu cose/fructose mixture, glycerol), and at. different pH values. From this mo del and using cardinal values extracted from the literature, theoretical ev olutions of the RGR of enicillium roqueforti, and Paecilomyces variotii, we re proposed and superimposed on data published in the literature. The resul ts showed a good concordance between the predicted and the observed values for these species. The use of this model in Predictive Microbiology is disc ussed. (C) 2001 Elsevier Science B.V. All rights reserved.