Modelling the cooking process of a single cereal grain

Abstract

Four models are developed to assist with the uniform and accurate cooking of whole grains for Uncle Tobys breakfast cereals.

1. Heat satisfies a linear conduction equation and is found to rapidly penetrate the grain.

2. Moisture satisfies a non-linear diffusion equation, and is found to penetrate the grain more slowly than heat. The more sophisticated moisture diffusion model is solved by numerical and analytic techniques for spherical and ellipsoidal grains.
A vital role is played in the moisture diffusion model by the concept of the mean action time for wetting a grain.
These first two models are used to determine sensitivity to key cooking parameters, and to calculate the degree of over-cook in the existing batch steam process. Recommendations are made for improving and speeding up the cooking process.
The last two models are modifications of the nonlinear moisture penetration model 2. above. The results of these improved models have the potential to provide finer adjustments to estimates of wetting times.

3. A cereal grain swells significantly during wetting. A model that takes this into account is developed and solved approximately.

4. Another wetting model describes the effect of the gelatinisation reaction, slowing moisture penetration, and leading to a sharp front entering the grain. The effect of gelatinisation on the speed of moisture penetration is expected to be more important for the present high-temperature cooking process, than when soaking a grain at a lower temperature. This model is also developed and solved approximately.