Effects of hot air, vacuum infrared, and vacuum microwave dryers on the drying kinetics and quality characteristics of orange slices

Abstract The present study aimed to dry orange slices at 50, 60, and 70°C using vacuum microwave dryer (VMD), vacuum infrared dryer (VID), and tray dryer (TD) and to compare the effects of different drying techniques on drying kinetics and product qualities. For this purpose, drying kinetics, total phenolic content, vitamin C, pH, total titratable acidity, bulk density, and color values of dried orange slices were evaluated. The VMD significantly increased the drying rates and the effective moisture diffusivities of orange slices compared with the VID and the TD. The drying times of orange slices for the VMD, the VID, and the TD at 70°C were detected as 69, 92, and 180 min, respectively. The experimental data were fitted to six thin‐layer drying models with R 2 range between .929 and 1.000. The results showed that the VMD had the smallest change in total phenolic content, vitamin C, pH, total titratable acidity, bulk density, and color values ( L *, a *, b *, Δ E , Δ C , and Hue°) of dried orange slices, whereas the TD had the highest changing. Practical applications Drying is a common preservation technique used for the long‐term durability of fruits and vegetables. This technique decreases the cost of storage, packaging, and transport of fruits and vegetables. Nevertheless, the traditional drying technique has some disadvantages, such as low energy efficiency, long process times, and a reduction in quality characteristics. The vacuum microwave dryer (VMD) and the vacuum infrared dryer (VID) have advantages such as higher drying rate, lower drying time, homogeneous temperature, high‐energy efficiency, and good product quality. In the industry, the VMD and the VID can be used as an alternative to the hot air drying, making the drying process faster for the fruits and vegetables.