The development of mathematical model of low-temperature vacuum drying of cheeses

The research objective was to develop mathematical model for the calculation of the duration of the process of vacuum drying of cheeses depending on the temperature of drying, the density of thermal stream, the size of residual pressure and the area of the dried-up cheese. The temperature for drying hard rennet cheeses (with a mass fraction of moisture of 40-42 %) was changed ranging from 50 to 80 °C with a step to 10 °C, thermal loading in various experiments was equal: 9.2; 8.28; 7.36; 6.44; 5.52; 4.6; 3.68; 2.76; 1.84; 0.92 kW/m². When heat was applied to the dried product, the surface layer of the material was most overheated, so drying process was controlled by the temperature of the surface layer of cheese. Rational temperature of vacuum drying of hard rennet cheeses was 60 °C, and rational value of the heat load was 5.5 kW/m2. The graphs of changes in the heat flux density, temperature, and relative mass of cheese during vacuum drying of cheeses were given. The schedules of the change of heat flux of density, the temperature and relative mass of cheese in the course of vacuum drying of cheeses were provided. Mathematical description of real process of vacuum drying of foodstuff was rather complex and labor-consuming challenge. Therefore for the description of this process some main assumptions were used. The calculations according to the description of the process of vacuum drying of cheeses were made mathematically. The model has been developed for calculating the duration of the cheese vacuum drying process depending on the drying temperature, heat flux density, residual pressure and the area of dried cheese.