DRYING KINETICS AND QUALITY OF APPLES AFTER DRYING WITH PRELIMINARY OSMOTIC DEHYDRATION

摘要

This paper examines the influence of apple osmotic dehydration (OD) on the kinetics of convective drying and the quality of obtained products.Fresh apples (Malus domestica) variety Ligol were used as experimental material.Samples were dehydrated first in the solution of three osmotic agents (glucose,fructose and sucrose),each of 40％ concentration,for 30,60 and 120 minutes,and next dried convectively.The efficiency of osmotic dewatering was assessed on the basis of water loss (WL) and solid gain (SG).The influence of OD on convective drying kinetics was analyzed by comparison of the drying curves and the basic kinetic parameters (time and rate of drying).The quality of products was assessed on the basis of colorimetric measurements and sensory evaluation.It was stated that OD allows to improve significantly the quality of dried products through better retaining original color,shape,texture,aroma and taste,but not affect remarkably the rate of convective drying.