The process of drying food is extremely complex. Therefore, the mathematical modeling of the process needs high requirements. The combination of approaches in modeling is of practical interest. On the one hand, analytical solutions based on the application of physical laws or phenomenological equations are used. On the other hand, experimental identification of the relationship between temperature and body moisture, which is considered as a peculiar characteristic of heat and mass transfer for each material. It is proposed to consider vacuum microwave drying from the standpoint of physical chemistry as a quasitopochemical heterogeneous reaction and perform mathematical modeling of this process based on the laws of chemical kinetics.

At the present time the maim quantity of free-running food products, including grains, are dried in units with convective method of heat input. To intensify convective drying, general attention is paid to improving the method of moving and mixing the product with drying agent, to guarantee fast and quality drying. The use of high and super-high frequency allows can significantly intensify the drying processes, because the phenomenon of super-high frequencies energy into heat conversion throughout the processed material volume contributes to the most uniform heating of the product, compared to other heat input methods. The optimal solution for drying free-running food products is a combination of convective and high-frequency heat input methods. This combination allows controlling gradients of moisture content and temperature, changing its directions, which significantly affects quality of the resulting dry product. In this regard, combined approach to drying process modeling is of practical interest: on the one hand, there are used analytical solutions, based on physical laws application or phenomenological equations, and, on the other hand, experimentally established a relationship between temperature and moisture content of media, which is considered as a heat and mass transfer characteristic for each material.

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