Low‐temperature microwave‐assisted drying of sliced bitter melon: Drying kinetics and rehydration characteristics

Abstract

AbstractIn this study, 5 mm thick thin layers of bitter melon (Momordica charantia L.) were microwave‐assisted dried at a low temperature on a laboratory scale. Bitter melon was selected as a material due to its nutritional value and therapeutic effectiveness. In this study, the full‐factorial design with microwave power densities (1.5, 3.0, and 4.5 W/g) and air‐drying temperatures (20, 25, and 30°C) was used to investigate the kinetics of drying and various soaking temperatures (25, 50, and 80°C) for each of the tested drying conditions was used to study the rehydration characteristics. According to the results, both the Weibull and Midilli models were determined to be the best‐fitting models for predicting the variation in moisture ratio during microwave‐assisted drying at low temperatures. At low drying temperatures (less than 30°C), the presence of microwave radiation would considerably enhance moisture diffusion. The moisture diffusion coefficient was determined to be between 1.14 × 10−8 and 2.59 × 10−8 m2/s when microwave power density varied from 1.5 to 4.5 W/g and temperature varied from 20 to 30°C. In low‐temperature microwave‐assisted drying, the rehydrated properties of dried bitter melon were significantly affected by microwave power. The kinetic rate and characteristic constants of the Peleg model were specifically decreased by the rise in microwave power density.Practical applications The first time, the drying and rehydration kinetics of sliced bitter melon were investigated using a relatively new drying technique, low‐temperature microwave‐assisted drying. Midilli and Weibull models are the best empirical models for describing the drying behavior of sliced bitter melon dried by low‐temperature microwave‐assisted drying, while the Peleg model is good for identifying the rehydration behavior. The microwave power density played a crucial role in the rehydration characteristics of dried bitter melon by low‐temperature microwave‐assisted drying.