Purpose: Development of a predictive tool using challenge tests and mathematical models to determine the time of appearance of the mold on pastries, according to measurable environmental factors ( T°, aw).
Methods: Rosso model has been used to describe and evaluate the cardinal values of the water activity and temperature for Aspergillus candidus. Instead of the optimal growth rate (µopt), it is proposed to use the minimum time of appearance of mold which was determined on food product. Indeed mold growth rate is fast and industrial issues mainly refer to appearance time, i.e., when is my product spoiled? The minimum time of appearance on pastries (1/Ta) was determined on cakes after storage at 25°C. Developed mathematical tool was further validated on cakes produced at a pilot scale or transferred by industrials.
Results: In the range of water activity from 0.7 to 0.9 and a temperature range from 15 to 25°C, a total of 55 cakes were inoculated with Aspergillus candidus. The results show that the aw measured on cakes vary over time. The water activity value to be taken into account in the simulation was the awof equilibrium (after 2 weeks storage). Results of simulation were then very close to the observed data (R² = 0.85; BF = 0.98; AF = 1.10). At this stage, for formulation without preservative, developed model provide satisfactory prediction of the time of appearance of molds as a function of water activity and temperature.
Significance: This study shows that predictive models developed for simulation of bacteria growth can be used to describe the apparition of molds on bakery products. The model will be useful to food microbiologists and manufacturers whose aim is to predict the likelihood of fungal spoilage as well as the development of new formulations minimizing fungal growth.