Modelling moisture uptake in a cereal grain

auther to whom correspondence should be addressed. Email: k.landman{at}ms.unimelb.edu.au.E-mail: cpp{at}maths.soton.ac.uk Recent experimental data have revealed the spatial and temporalstructure of moisture content within a cereal grain immersedin boiling water. A simple model of the water's motion is presented,guided by the observed behaviour, which allows for nonlinear(exponential) diffusion within the grain and a constant mass-transfercoefficient to represent the pericarp on the outer surface.Numerical results are presented illustrating the close relationshipof the predictions to the experimental results, with the mass-transfercoefficient as a fitting parameter. The model is studied usingasymptotic analysis, in the limit of large activation energyin the diffusion coefficient and large mass transfer. The analysisgives insight into the three phases of the process, consistingof initial linear diffusion, linear motion of the moisture frontinto the grain, and slow filling of the grain in a relativelyuniform manner. The problem is also studied using mean-action-timeanalysis to derive simple expressions for the time for the grainto saturate.