Modeling the impact of water activity, pH, and calcium propionate on the germination of single spores of Penicillium paneum

Abstract

This study aimed to assess the effect of water activity (aw) (0.93–0.95), pH (5.1–5.8), and concentration of calcium propionate (0.25 and 0.41%) on the germination time of individual spores of Penicillium paneum. The germination of single spores was examined by capturing images at every hour using the Axio Observer.Z1 inverted microscope ( × 100) connected to the camera at 25 °C for 96 h. The results indicated that P. paneum germination time was significantly affected by aw and pH (ρ < 0.05). As most of the growth curves exhibited asymmetric shapes, the asymmetric model was fitted to germination data and the maximum percentage of viable spores (Pmax; %), shape parameter (d), and germination time (τ; hour) were obtained. τ -values ranged from 26.5 to 40.7 h. After the Monte Carlo simulation, a probability distribution of time for 10% of the P. paneum population (t10%) to germinate was obtained. The mean value of t10% was 25 h, ranging from 15 to 47 h (95% confidence interval). The variability in germination and growth of P. paneum single spores highlights the challenge of predicting and preventing this critical phenomenon.