Study of pretreatment methods for peach drying

The pretreatment for peach drying is essential to enhance the efficiency of the drying process. This paper investigates the impact of various pretreatments (ethanol, ultrasound in water and ethanol, and microwave) on hot-air drying, microwave drying, and hot-air combined with microwaves (microwave finishing). Hot air drying revealed that ethanol pretreatment significantly reduced drying time by up to 23.5%, attributed to its osmotic effect and ability to dissolve food matrix constituents. Ultrasound pretreatment showed mixed results, with high amplitude (90%) and extended duration (30 min) yielding a 17.6% reduction in drying time. Microwave pretreatment demonstrated remarkable efficiency, reducing drying time by 58.8%, attributed to volumetric heating and steam flow induced by microwaves. Diffusion coefficients were calculated, with ethanol pretreatment exhibiting positive effects, while ultrasound and microwave pretreatments showed varying influences. Microwave drying post-pretreatment drastically reduced drying time, and the efficiency was further evaluated through microwave-finishing. Ethanol and ultrasound pretreatments improved final moisture content and drying rates during both drying stages, while microwave pretreatment resulted in severe overheating and quality loss. The scanning electron microscope images showed variations in the microstructure of the pretreated peach cubes compared to untreated ones. Ethanol pretreatment led to a more compact structure, while ultrasound pretreatment in water resulted in a porous structure. The combination of ethanol and ultrasound pretreatments exhibited more pronounced effects, particularly for hot air and microwave-finishing drying, where the cubes showed significant deterioration.