Ultrasonic-Microwave and Infrared Assisted Convective Drying of Carrot: Drying Kinetic, Quality and Energy Consumption

In this study, the drying time, effective moisture diffusivity (D-eff), specific energy consumption (SEC), and quality (color, shrinkage, and rehydration) of the ultrasound-pretreated (US) carrot slices were compared when dried by hot air drying (HD), microwave drying (MWD), infrared drying (INFD), and hybrid methods of MW-HD and INF-HD. Five mathematical models were considered to describe the drying kinetics in the carrots. The results show that US+MW-HD and INFD were the fastest and the slowest drying techniques compared to the HD technique with a 73% and 23% drying time reduction, respectively. TheD(eff)ranged from 7.12 x 10(-9)to 2.78 x 10(-8)m(2)/s. The highest and lowest SECs were 297.29 +/- 11.21 and 23.75 +/- 2.22 MJ/kg which were observed in the HD and US+MWD, respectively. The color variation indices indicated that the best sample in terms of color stability was the one dried by US+MW-HD with the color variation of 11.02 +/- 0.27. The lowest and highest shrinkage values were also observed in the samples dried by US+MWD and HD (31.8 +/- 1.1% and 62.23 +/- 1.77%), respectively. Samples dried by US+MWD and HD possessed the highest and lowest rehydration, respectively. Although the carrot slices dried at a higher pace by US+MW-HD (compared to US+MWD), the shrinkage and SEC of the samples dried by US+MWD were significantly lower than the US+MW-HD (p< 0.05). Therefore, it can be concluded that the application of the US+MWD method can be considered as a proper alternative for drying the carrot slices when compared to the HD, MWD, INFD, and hybrid methods.