Modeling the effect of temperature and water activity on the growth rate and lag phase of Aspergillus flavus during rice drying

The objective of the present study was to develop validated models that describe the effect of storage temperature and a(w) on the growth rate and lag phase of Aspergillus flavus in rice. The colony growth rate and lag phase were estimated by fitting a primary growth model. Afterwards, a secondary model relating colony growth rate or lag phase to a(w) and temperature were developed and validated by using independently collected data. The linear Arrhenius-Davey model describing the effects of temperature on colony growth rate or lag phase proved an adequate predictor. The developed quadratic polynomial function was validated for rice. The obtained bias factors ranged from 0.893 to 0.957 and the accuracy factors were < 1.15, indicating that the model was a good predictor for describing the combined effect of a(w) and temperature on the colony growth rate and lag phase. A. flavus had optimum growth at temperatures of approximately 31 degrees C. The developed models can be applied in the preservation of rice and the development of models that incorporate other factors important to mold growth in rice.