Water and salt diffusion during cheese ripening:: effect of the external and internal resistances to mass transfer

High humidities of drying medium lead to lower drying rates, and both external or internal conditions determine the drying rate. Thus, a diffusional model has been developed assuming that the external resistance to mass transfer could not be neglected in these cases and solved by a finite difference method. The external mass transfer coefficient was estimated from the literature. This mathematical model was used to identify water and salt effective diffusivity coefficients by using experimental data of ripening experiments carried out on parallelepipedal Mahon cheeses of 0.14 m x 0.14 m x 0.09 m edges kept at 12 degreesC and 85% RH. Using these identified values, 7.8 x 10(-12) m(2)/s for moisture diffusion and 5.3 x 10(-10) m(2)/s for salt diffusion, average moisture content and water and salt profiles during the ripening of 0.20 m x 0.20 m x 0.10 m cheeses ripened at 12 degreesC and two different relative humidities, 70% and 80% RH, were accurately simulated. (C) 2001 Elsevier Science Ltd. All rights reserved.