In this paper, it was attempted to determine the effect of the kind of osmotic substance and pressure as applied during the pre-treatment on changes in the tissue of osmotically dehydrated and convectively dried apples. It was found that the efficiency of the dehydration process and the character of changes depended on the pressure and kind of osmotic substance applied. In the case of apples osmotically dehydrated (pretreatment), next, when they were convectively dried, the rate of removing water from them decreased in the entire range of variability of water content studied. It was found that, after the completed convectional drying of apples dehydrated under a lower pressure, the final water content in those apples was lower regardless of the kind of osmotic substance. At the same time, those apples are characterized by higher water activity levels compared to the apples dehydrated under the atmospheric pressure conditions. Osmotic dehydration under the lower pressure caused a considerable increase in the solid gains; this fact caused the content of sugars in the tissue of apples to increase and the course of convection drying to change. The diffusion coefficient of water in osmo-convectively dried apples depended both on the pressure and on the kind of osmotic substance.
apples, convective drying, osmotic dehydration, low pressure