Thin Layer Drying Kinetics of By-Products from Pomegranate Juice Processing

Abstract

Drying of pomegranate by-products that are formed at the instance of pomegranate juice processing was studied at 50, 60, 70 and 80C while air velocity was 2 m/s. The results obtained show that moisture content of the by-product decreases with time and temperature. The drying process takes place mainly in the falling rate period. Several thin-layer drying models were selected to describe experimental drying kinetics data. The models were compared based on their coefficients of determination (R2), reduced chi-square (χ2) and root mean square error (RMSE) between experimental and predicted moisture ratios. Consequently, the Midilli et al. model was selected as the best mathematical model for describing the drying kinetics of the pomegranate by-products. The effective moisture diffusivity of pomegranate by-product varied from 1.22 × 10−10 m2/s to 4.29 × 10−10 m2/s. The activation energy was calculated as 39.66 kJ/mol using Arrhenius-type equation. Practical Applications Pomegranate is an important commercial fruit crop that is extensively cultivated all over the world in tropical, subtropical and temperate zones. It is mainly consumed as a raw staple food and used to mix in jams, jellies, teas, beverages, and concentrated in syrups and liqueurs. The process of pomegranate juice production remains large quantities of pomegranate by-products such as peels and seeds. The by-products due to high initial moisture content are very sensitive to microbial spoilage. Drying is one of the preservation methods applied to agricultural products. The basic objective in drying agricultural products is the removal of water in the solids up to a certain level, at which microbial spoilage and deterioration chemical reaction are greatly minimized. Besides, knowledge of drying characteristics is important in the design, simulation and optimization of drying process.