Shrinkage Kinetics during Convective Drying of Selected Berries

Abstract

Drying and shrinkage kinetics of gooseberry, black and red currants, cherry, and blackberry were studied using a fully automated experimental apparatus, designed for continuous monitoring of the material moisture content, its temperature, and surface area. Experimental drying curves were approximated with a modified exponential model. The volume and surface area of berries were determined from the pictures taken during drying and transformed into digital images. The procedure for calculation of the object-related pixels in a two-dimensional plane to the temporal three-dimensional volume and surface area of the berries was developed. The modified exponential model was proposed to correlate the volumetric and surface area shrinkage with moisture content. Volumetric shrinkage at the end of drying was maximal (0.3) for black currant and minimal (0.45) for gooseberry.

Keywords:

• Blackberry
• Black currant
• Cherry
• Drying curves
• Drying kinetics
• Gooseberry
• Red currant
• Shrinkage
• Temperature curves