The objective of the study was to determine the effect of the solution concentration, temperature, and process time on changes in water content and on process efficiency of osmotic dehydration of apples. The samples shaped as a 25×25×10 mm plate were osmotically dehydrated in a 20, 40 or 60 % sucrose solution at temperatures of 20, 40 or 60 ºC during 60, 180, or 300 minutes. While the apples were osmotically dehydrated, the quantity of removed water (water loss) and solids gain in the apples increased along with the increase in the sucrose concentration level and along with the increasing temperature; also, the penetration of osmotic substance (solids gain) was higher. The effect of sucrose solution concentration on the substance exchange in apples being dehydrated was higher than the effect of temperature. If the process run in a 20 % sucrose solution, the tissues of apples were insufficiently osmotically dehydrated. In the apples kept in the sucrose solution, the penetration degree of osmotic substance (solids gain) was higher than the water removal degree (water loss). Probably, in some cases, the water was not removed from the apples, on the contrary, the water content increased. As a result, the efficiency of the process expressed as a ratio of water loss to solids gain was a negative value. Along with the increase in concentration of the sucrose solution and in the temperature of dehydration process, the rate of removing water from the apples examined increased. The penetration rate of osmotic substance into apples at t = 20 ºC did not depend on the sucrose solution concentration nor on the time of dehydration process. The application of a constant temperature of dehydration of apples (20 ºC) and a varying concentration value of sucrose solution (20, 40, or 60 %) caused that the penetration rate was the highest in the apples dehydrated during 60 minutes in a 40 % sucrose solution. When the osmotic dehydration process was carried out in a constant (not changed) 40 % sucrose solution and at t = 20, 40, or 60 ºC, the highest rate of penetration was in the apples that were dehydrated during 60 minutes at t = 40 ºC .
apples, osmotic dehydration, water loss, solids gain