Effects of osmotic pretreatment on quality and physical properties of dried quinces (Cydonia oblonga)

Abstract

© 2015 National Agricultural and Food Centre (Slovakia). The aim of this study was to examine the effects of osmotic pretreatment on some physical properties of quinces. Osmotic drying was performed in a saccharose and water solution. The temperatures of osmotic solution were 40 °C and 60 °C, and the initial concentrations were 50 °Bx and 65 °Bx. All four combinations were used in the experiment. High values of the total colour change E* were recorded following the treatment of quince samples with the osmotic solution of 65 °Bx. Lower values of the total colour change were recorded in the same samples after convective drying. Slighter changes in colour after convective drying were caused by a greater amount of solute retained on the surface of the fruit, forming barriers between the fruit tissue and the surrounding air. Mechanical properties of quinces during osmotic drying expressed by the force ratio f = (F0 - Fi)/F0 and modulus of elasticity showed dependence on the temperature of the osmotic solution. At 60 °C, the osmotic solution caused softening of the quince tissue. Thermal softening had a positive influence on the naturally hard quince tissue. The results of the study demonstrate positive effects of osmotic drying on physical properties and quality of dried quinces.