Mathematical Modeling of Moisture Distribution and Kinetics in Cheese Drying

In the cheese industry, the longest phase in the manufacture of cheese is ripening, during which a considerable loss of water occurs. An understanding of the mass transfer mechanisms of drying would thus contribute to improving engineering design and the quality of the final product. In this work, a mathematical model for a cubic shape was proposed to predict the drying kinetics and moisture distribution during cheese drying. The model was developed taking into consideration both the external and internal resistances to mass transfer and an effective diffusion dependent on local moisture and temperature. Furthermore, a specific model for sorption isotherms was established from experimental results and used to complete the overall model formulation. The drying experiments were carried out at 6.3, 12.2, and 18.2 degrees C and 1.0 m s(-1) until a moisture content of approximately 0.30 kg kg(-1) (db) was reached. Moisture distribution was experimentally measured from the center of the cheese cube to the center of the surfaces and to the vertexes using a time-domain nuclear magnetic resonance (TD-NMR) method. The proposed model was solved using a finite element method and validated by comparing the experimental moisture profiles with those simulated by the model. A satisfactory simulation was obtained for both the drying curves and the moisture profiles. For both groups of data, a mean relative error lower than 6% and a percentage of explained variation higher than 97% was achieved.