[Selection of a mathematical model for drying kinetics of sour cherry [Prunus cerasus L.] in a microwave-vacuum dryer]

ABSTRACT

In the recent years, the application of microwave-vacuum drying as a novel, effective, and low-cost method for dehydration of various foods has been investigated. Therefore, the objective of the present study was to evaluate the potential of this method in drying sour cherry, as well as to select an appropriate mathematical model for describing its drying kinetics. The experimental drying trials were performed at 4 nominal microwave power levels [360, 600, 840, and 1200 Watts] and 4 absolute pressures [200, 400, 600, and 800 mbar] using a microwave-vacuum dryer designed in our laboratory. The drying parameters were determined as functions of absolute pressure and microwave power. Moreover, the fitting rates of experimental data with seven semi-theoretical and empirical models based on R2, chi2 and RMSE values were determined and the most appropriate mathematical model was selected. The findings showed that the microwave power and the vacuum level play the major role in the drying rate of sour cherry, such that increasing microwave power and decreasing the drying chamber pressure reduce the drying time significantly. Moreover, the drying process occurred in the falling rate period. Comparison of different models showed that the Middili and co-workers model can be the most suitable model due to its having the highest R2 and lowest chi2, RMSE values. The findings of this study indicate that the drying process of sour cherry does not show any constant drying rate during dehydration using a microwave-vacuum dryer. Thus, microwave-vacuum drying has a high potential for dehydration of sour cherry and other food and agricultural products due to high efficiency and reasonably short proceesing times