Abstract Suspensions of wheat, corn or rice starch, containing 5% polymer, were heated to temperatures in the range 20–145°C in a differential scanning calorimeter (DSC). Once the desired temperature was reached, the sample was immediately cooled at a rate of 320°C min −1 to room temperature. The numbers of native and gelatinized granules in the sample were then determined by microscopy. The variation in the fraction of gelatinized particles with temperature was found to follow a normal distribution function. A mathematical model based on this function was developed in an attempt to understand the DSC traces. The model predicts the shape of the gelatinization endotherm and accounts for the fact that the temperature band over which the endotherm takes place is broader than that for the birefringence loss. The model also suggests that the heat flow into an individual granule decreases as gelatinization proceeds therein.