Microwave and convective drying kinetics and thermal properties of orange slices and effect of drying on some phytochemical parameters

Abstract

We dried the orange slices massed 100 +/- 0.10 g from the initial moisture content of 6.97 +/- 0.02 kg(water) kg(DM)(-1) to the final moisture ones of 0.12 +/- 0.01 kg(water) kg(DM)(-1) using two different drying methods defined as convective drying at 50, 75, 100, and 125 degrees C along with microwave drying at eight output power between 90 and 1000 W. In the study, we measured the drying methods' energy consumption and observed that the microwave drying method's energy consumption was very low at high and low powers. Also, we modeled the results using twenty-one different thin-layer drying equations and obtained results closest to experimental data with the modified Henderson and Pabis equation for all powers in microwave drying and all temperatures in convective drying. We calculated both effective moisture diffusivities and activation energy using the drying data. Some thermal properties such as specific heat, thermal conductivity, thermal diffusivity, and thermal effusivity were calculated and recorded to be decreasing in all thermal properties with drying. Also, we measured the color parameters known as L, a, b, C, alpha degrees, and Delta E, browning index (BI), whitening index (WI), and vitamin C (ascorbic acid) in the study. We concluded that the most suitable drying method is microwave drying at medium powers of 350 and 500 W by considering both drying and quality parameters.[GRAPHICS].