Convective drying of cape gooseberry fruits: effect of pretreatments on kinetics and quality parameters

Abstract

The effect of physical (fast freezing with liquid nitrogen and slow freezing followed by thawing) and chemical (alkaline solution of ethyl oleate) pretreatments on the kinetics and quality parameters of cape gooseberry (Physalis peruviana) during convective drying (60 °C, 2 m/s) was studied. The influence of the pretreatments on the drying kinetics, shrinkage, rehydration capacity, ascorbic acid retention, water activity, textural profile, and color were evaluated. Five thin-layer equations were evaluated for their ability to predict the drying kinetics, of which the Wang & Singh equation performed best. All of the pretreatments reduced the drying time by reducing the resistance of the waxy skin of the gooseberry to mass transfer. The chemical pretreatment promoted the shortest drying time and the highest ascorbic acid retention, rehydration capacity, the best maintenance of texture, as well as the least shrinkage.