PREDICTING FUNGAL GROWTH - THE EFFECT OF WATER ACTIVITY ON ASPERGILLUS-FLAVUS AND RELATED SPECIES

Growth of four species belonging to Aspergillus Section Flavi (A. fluv us, A. oryzae, A. parasiticus and A. nomius) was studied at 30-degrees -C at ten water activities (a(w)) between 0.995 and 0.810 adjusted wit h equal mixtures of glucose and fructose. Colony diameters were measur ed at intervals and plotted against time. A flexible growth model desc ribing the change in colony diameter (mm) with respect to time was fir st fitted to the measured growth data and from the fitted curves the m aximum colony growth rates were calculated. These values were then fit ted with respect to a(w) to predict colony growth rates at any a(w) wi thin the range tested. The optimum a(w) for each species and time to r each a colony diameter of 3 mm were also calculated.