DRYING AND REHYDRATION CHARACTERISTICS OF SOUR CHERRY (PRUNUS CERASUS L.)

Abstract

The effect of air temperature and velocity on the drying kinetics of sour cherry was investigated using a laboratory scale static‐type dryer at air temperatures of 60, 70 and 80C and air velocities of 0.3, 0.6 and 0.9 m/s. The Weibull distribution model was fitted to experimental data using nonlinear regression analysis techniques in the MATLAB computer program. The high regression coefficients (R² > 0.998) and low reduced chi‐square and root mean square error indicated that the Weibull model is suitable for predicting moisture ratio. Correlations of the Weibull model constants with the variables T and V were determined. The effective diffusivity of sour cherry varied between 3.46 × 10^‐9 and 13.08 × 10^‐9 m²/s. The activation energy of sour cherry was in the range of 64.39–66.05 kJ/mol. Rehydration tests indicated that the rehydration capacity of dried samples at air temperature of 70C and air velocity of 0.3 m/s is better than other experiments. PRACTICAL APPLICATIONS All commercial flow dryers are designed based on thin‐layer drying principles. One of the most important aspects of drying technology is the modeling of the drying process. The prediction of drying kinetics of agricultural products under various conditions is very useful in design and optimization of dryers. In this paper, the Weibull distribution model is used for modeling thin‐layer drying of sour cherry. Weibull's model constants include the effect of drying variable on drying kinetics and could be a useful tool for the modeling of drying kinetics. The rehydration characteristics of a dried product are used as a quality index and they indicate the physical and chemical changes during drying as influenced by processing conditions, sample pretreatment and composition. Optimizing the drying conditions in order to obtain the dried product with good rehydration characteristics is vital, since rehydration governs the subsequent operations.