Effect of Microwave Power Coupled with Hot Air Drying on Sorption Isotherms and Microstructure of Orange Peel

Drying is one of the most cost-effective methods of worthwhile by-product valorisation. This study had two main objectives. The first was to determine the effect of hot air drying (HAD) combined with microwave (MW) irradiation on the treatment kinetics and the macrostructural and microstructural properties of the dried product. The second aim was to develop engineering tools to predict the extent of dehydration. Drying was performed using hot air at 55 A degrees C and the combined (HAD + MW) treatment at different power intensities (2, 4, and 6 W/g). After 5, 15, 40, 60, and 120 min, the mass, surface, volume, water activity and moisture were measured in fresh and dried samples. Sorption isotherms were obtained and fitted to the GAB model, with high correlation coefficients. The macroscopic and microscopic analyses showed shrinkage and swelling in the peel tissue caused by the MW treatment. The HAD + MW methods not only resulted in increased moisture reduction but also induced microstructural changes that generated higher sorption capacity.