Mathematical modeling of hot-air drying process of quince slices with pretreatment of osmotic dehydration: Determination of effective diffusivity coefficient and activation energy

Pretreatment of osmotic dehydration in hot-air drying process is used with the aim of improvement in the nutritional, sensory and quality properties of the final dried product. In present study, the pretreatment of osmotic dehydration of quince slices and then hot air drying of it was performed. Osmotic dehydration was done in concentrations of 40, 45 and 50% sucrose and hot-air drying temperatures of 40, 50 and 60 °C. The ratio of sample to osmotic solution and also the temperature of osmotic solution were considered as 1:10 and 30 °C, respectively. Mathematical modeling of hot-air drying process of quince was evaluated using models of Newton, Page, modified Henderson and Pabis, simplified Fick diffusion, Modified Page equation-II, two-term, Wang and Singh, and logistics. The fitting of the experimental data with models was done in order to determine the optimum model to describe the drying process, determination of effective diffusivity coefficient and activation energy. Drying time for untreated sample at 40, 50 and 60 °C was 509.671±1.527, 491±1.732 and 459.500±0.707 min, respectively. In addition, for samples with pretreatment of osmotic dehydration, drying time at studied temperatures of air drying was decreased with increase of sucrose concentration in osmotic solution. Page model was determined as the best model for describtion of mass transfer kinetic during drying of quince. The concentration of 50% osmotic solution and temperature of 60 °C resulted to effective diffusivity coefficient of 2.817×10-10 (m2/s) and drying time of 286±1.413 min. Furthermore, effective diffusivity coefficient was increased with an increase in air drying temperature. The concentration of osmotic solution was also related inversely to activation energy. Sensory evaluation showed an increase in concentration of osmitic solution caused an increase in overall acceptability.