Osmotic and convective drying of strawberries: Effects of experimental parameters on the drying kinetics, color and rehidratation

Abstract

The objective of this research was to investigate the influence of osmotic dehydration as a pre-treatment to the air drying of strawberries. Fresh, untreated strawberries were sliced and dried in a sucrose solution at a temperature of 50 oC and concentrations of 50 and 65 oBx. After osmotic dehydration, the slices were dried in a thin layer at air temperatures of 60, 70 and 80 oC, and an air velocity of 1 m/s. After osmotic dehydration, the moister content and solid gain at a sucrose solution concentration of 55 oBx were 3.44 gw/gdm and 0.062 gdm/g, respectively. However, the moister content and solid gain in at a sucrose solution concentration of 65 oBx were 4.08 gw/gdm and 0.0944 gdm/g (65 oBx), respectively. The effective moisture diffusivity of air drying varied from 1.57 x 10-9 to 4.43 x 10-10 m/s2, increasing with an increase in air temperatures and decreasing with an increase in pretreatment source concentrations. Lower air temperatures exert a positive influence on the rehydration time. A shorter air drying process positively affects the total changes in colour. The impact of pretreatment on colour changes in strawberries was not recorded after drying.

Keywords

• strawberry
• osmotic dehydration
• air drying
• rehydration
• color