Comparison between continuous and intermittent drying of whole bananas using empirical and diffusion models to describe the processes

Four experiments were carried out with continuous and intermittent drying of whole bananas, using hot air. Three intermittent processes were performed with the same intermittency ratio (1/2), with intermittency times of 0.5, 1.0 and 2.0 h. Dimensionless moisture content as a function of the effective operation time was described by empirical and diffusion models. Peleg model enabled to observe that eight hours of continuous drying were equivalent to four hours of discontinuous process with 1 h of intermittency. In addition, this model enabled to determine an expression for drying rate and to observe that discontinuous process increase the value of this rate. Diffusion model with boundary of the third kind described well the drying processes and made it possible to realize that the mass transfer Biot number was reduced from 11.5 (continuous) to 0.6 (1 h of intermittency), indicating that in the discontinuous case the product is submitted to smaller stresses. (C) 2015 Elsevier Ltd. All rights reserved.