Effect of water activity and temperature on growth of three Penicillium species and Aspergillus flavus on a sponge cake analogue

This study compared the effect of temperature and water activity and their interactions on the rate of mycelial growth of Penicillium aurantiogriseum, P. chrysogenum, P. corylophilum and Aspergillus flavus on a sponge cake analogue. As expected, growth rates showed dependence on aw and temperature. However, no significant differences were observed in the growth rates of different isolates. The minimum aw values for growth of the Penicillium spp. was 0.85–0.90. A. flavus was able to grow at 0.90 aw when the temperature was above 15 °C. This study has shown that fungal growth by these species on a sponge cake analogue, with a composition similar to usual bakery products, is prevented if the aw is kept at <0.85.