Application of Doehlert design to determine the combined effects of temperature, water activity and pH on conidial germination of Penicillium chrysogenum

Aims: The influence of temperature, water activity and pH on the time necessary for germination of 90% of Penicillium chrysogenum conidia inoculated (T90) was determined. Methods and Results: A new experimental device was developed for easy monitoring of the germination process. Experiments were carried out according to a Doehlert matrix at 11–31°C, 0·86–0·98 water activity (aw) and pH 3·5–6·5. In these conditions, a second order polynomial relationship between T90 and the environmental factors was established for the different humectants used throughout this study (e.g. glycerol and sorbitol) with regression coefficients close to 0·97. Conclusions: For both humectants, the major effect of temperature and water activity on T90 was highlighted, whereas the effect of pH on T90 in these experimental conditions was not significant. The combined effect of temperature and water activity on T90 was also demonstrated. Significance and Impact of the Study: Both the experimental set-up and the Doehlert matrix were well suited to determine the influence of environmental factors on mould germination.