Microwave–Vacuum Drying of Strawberries with Automatic Temperature Control

A microwave–vacuum drying system with the ability of automatic temperature control was developed for strawberry drying in order to obtain a high-quality product, in terms of appearance, color, and texture. Changes in quality attributes of strawberries were determined by measuring the color, texture, shrinkage, and rehydration. Microwave–vacuum drying (47 mm Hg) yielded an elastic product of improved mechanical resistance with just a slight loss of color and appropriate rehydration performance using automatic temperature control around 50 °C and 700-W power. The specific energy consumed during strawberry drying using automatic temperature control varied between 1.30 and 2.30 Wh/g. The efficiency of process in automatic mode was 13.5 times higher than efficiency in manual mode. A drying protocol for strawberries, based on automatic on–off temperature control, was developed. Thus, the drying temperature and dead band could be easily changed during the trials, and there is no need to tune the controller when drying a different kind of fruit.