Influence of preliminary osmotic dehydration on drying kinetics and final quality of carrot (Daucus Carota l.)

Abstract

This paper concerns convective drying of carrot preliminary dehydrated in aqueous solutions of three types of osmotic agents (sucrose, fructose, glucose). Three solution concentrations (20, 40 and 60%) were examined to work out efficient conditions of osmotic dewatering. The parameters such as water loss (WL), solid gain (SG) and osmotic drying rate (ODR) indicating the real efficiency of osmotic dehydrations (OD) were determined. The samples dehydrated with osmotic solutions underwent further convective drying to analyze influence of dehydration process on drying kinetics and final products quality. The quality of products was assessed on the basis of visual appearance of the samples and colorimetric measurements. It was found that osmotic pretreatment improves significantly the final product quality as the samples were less deformed and their colour was better preserved compared to samples, which had not been preliminarily dehydrated. Preliminary dehydration, however, did not influence significantly the overall drying time of the samples.