Effect of Osmotic Dehydration on Air-Drying Characteristics of Chayote

In this study the effect of osmotic dehydration (OD) on the air-drying kinetics of chayote (Sechium edule (Jacq.) Swartz) fruits was investigated. Fresh and osmotically dehydrated chayote parallelepipeds (1x1x2 and 4x4x2cm) were subjected to convective drying at air temperatures of 50 and 60 degrees C, with air velocities of 1.5 and 2.5m/s. The OD pretreatments were performed in 10 and 25% NaCl solutions (w/w) at 25 degrees C during 3h using a solution-to-fruit mass ratio of 4:1. The use of higher air velocities notably accelerated drying rates as manifested through significantly higher drying rate constants estimated with Page's model, whereas no effect of temperature was observed. A previously reported analytical solution that considers both product shrinkage and variable diffusivity was generalized to describe the drying kinetics of food products with parallelepiped geometry. Selected drying experiments were then fitted to this solution using six different sets of model assumptions. Results indicated that product shrinkage is the main factor to be considered in order to estimate reliable values for diffusion coefficients. The OD pretreatments produced a significant reduction of the initial moisture content of chayote slabs before drying, thus allowing shorter drying time, which may lead to reduced energy consumption.