Fingerprints of the drying behaviour of particulate or thin layer food materials established using a reaction engineering model

Drying is a subject of extensive research due to its importance in manufacturing many types of products. It has been modelled by adopting the drying characteristic curve method, the comprehensive transport phenomena approach or the entirely empirical correlations. This paper describes a mechanistic model of drying using a reaction engineering approach, i.e. assuming drying is a competitive process between 'evaporation reaction' and 'condensation reaction'. The maintenance of the conventional heat and mass transfer boundary treatment allows the change in the fluid flow conditions around the solid to be taken into account. The apparent activation energy for each material can be established as a function of water content while the relationship between activation energy and water content during drying of the material of interest may be taken as a fingerprint of the material. The large differences between the broken down structure (the well-dispersed system) and the cellular structure can be visualized by comparing the curves of activation energy with the water content.