Microwave Pre‐treatment for Sun‐Dried Raisins

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Commercial sun‐drying of raisins requires a long time, and chemical pretreatments are used to increase the drying rate. The feasibility of improving the sun‐drying process of grapes by microwaves was investigated. Sultana seedless grapes, dipped in alkali solution, were pre‐treated in a domestic microwave oven and dried by direct solar radiation. Microwave pre treatment reduced the moisture content by 10–20%. The microwave‐treated grapes dried nearly two times faster than the controls. Blanching in boiling water had the same effect on the drying rate as microwaves. Color and appearance of treated grapes were comparable to commercial products.