Aflatoxin B1 production: A time-water activity-temperature model

Aspergillus flavus occurs as a contaminant of various foods and animal feeds and can produce the mycotoxin aflatoxin B₁ that is a danger to human and animal health. Here, we develop models to predict the behaviour of A. flavus in maize extract agar and maize grains. Growth and aflatoxin B₁ production were recorded on maize extract agar at 20-35 °C and water activities from 0.84 to 0.90. We then obtained probability models-using temperature, water activity, and time as explanatory variables-based on data of growth and aflatoxin B₁ production. Additional data were generated under two dynamically changing temperature regimes. Initial water activity, and relative humidity during incubation, were recorded. Predicted probability of growth under dynamic conditions based on models built under static conditions depended on the temperature regime and substrate, concordance ranging from 66 to 100%, with lower concordances obtained for aflatoxin B₁ production prediction. Interestingly, aflatoxin B₁ production was higher on maize grains than on maize extract agar. Moreover, this work suggests that the safe water activity for a cereal may depend on the previous water activity and temperatures which may have allowed fungal growth and so trigger later toxin production under water stress.