Purpose: This study was conducted as a risk evaluation performed on storage of artisanal rice pie at different temperatures.
Methods: A survey was undertaken in 15 Belgian artisanal bakeries to evaluate variations in the production process. Internal microbiological contamination (total aerobic and total aerobic spore count), pH, and water activity (aw) were determined in 31 samples. Pilot experiments were undertaken to determine the internal pie temperature during the baking process. Simulations of Bacillus cereus growth were performed using Combase at pH and aw combinations corresponding to those observed. Results were validated by challenge tests.
Results: A large variation was found in receipt and baking conditions. Bacteria were counted in 5/31 samples (10 to 110 cfu/g), but spores were not found in any of the samples. The pH and aw of the rice pies varied between 6.3 and 7.03 and between 0.957 and 0995, respectively. During the baking process, it took at least 30 minutes to reach an internal temperature of 90°C. The baking time at >90°C was 0-40 minutes. Simulations using worst case combinations of pH and aw (pH 6.8 and aw 0.995) indicated a level of B. cereus of < 4 log cfu/ml (considered the limit for food safety) after storage at 20°C for 12h, when starting from 1 cfu/g. Challenge tests resulted in growth similar to that predicted by modelling.
Significance: The data suggested that a maximum level of B. cereus (4 log cfu/g) can be guaranteed in rice pie, if stored for 12h at ≤ 20°C.