Effect of Convective Dryness Combined with Osmotic Dehydration, Blanching, Microwave and Ultrasonic Treatment on Bioactive Compounds and Rehydration Capacity of Dried Plums

Abstract

Increasing interest in keeping bioactive compounds (anthocyanins, vitamin C) and dried fruit quality has motivated the researchers to investigate new combined drying technologies. The objective of this study was to evaluate the effects of convective drying combined with osmotic dehydration, bleaching, microwave treatment and ultrasonic treatment of bioactive compounds (anthocyanins, vitamin C), rehydration capacity and prune drying rate. Osmotic dehydration was achieved by maintaining plums for 1 hour in sucrose solution (300Brix). For microwave treatment, the plums were kept at 400 W for 80 s. For ultrasonic treatment, plums were immersed in distilled water and sonicated for 30 min at 40 kHz and 200 W. The blanching consists of immersing plums in hot water at 900C for 20 s and cooling them rapidly. Convective drying was carried out at 700C. Blanching led to the largest amount of evaporated water. The lowest reduction in anthocyanins, of 34.5%, was obtained for osmotic dehydrated plums. The prunes blanched before drying have had the highest rehydration capacity.