Prediction of conidial germination of Penicillium chrysogenum as influenced by temperature, water activity and pH

Aims: Conidial germination of Penicillium chrysogenum was carried out under operating conditions compatible with a pastries manufacturing process. Methods and Results: A range, limited by two experimental values, was defin ed for each environmental factor tested: temperature (15 or 25 degreesC), w ater activity (0.75 or 0.85) and pH (3.5 or 5.5). A closed device was made, which maintained an equilibrium between water activity of the culture medi um and atmospheric relative humidity during 25 days, to follow spore germin ation. The combined effects of temperature, water activity and pH on spore germination were studied by applying factorial design methodology. Conclusions: Higher rates of spore germination were associated with a high level of water activity. The incubation temperature also had a positive eff ect. A significant positive interaction between water activity and temperat ure was observed. Under these specific experimental conditions, pH did not have a significant effect on conidial germination. Significance and Impact of the Study: A model describing the behaviour of f ungal conidia is proposed.