Optimization of Osmotic Dehydration of Apples in Sugar Beet Molasses

Abstract

This paper describes the effects of different concentrations of sugar beet molasses (40–80%) and immersion times (1–5 h) on osmotic dehydration/impregnation of apple cubes. Osmotic dehydration process was conducted at constant temperature of 55C and under atmospheric pressure. Analysis of variance was used in order to find significant effects of solution concentration and immersion time on water loss, solid gain, carbohydrates and minerals content, as well as change in colors and textural characteristics. It was found that the influence of both process variables were statistically significant at P < 0.05 level, on almost all of examined responses, with the exception of minerals content (Ca and K content were found insignificant, while Na was found significant at P < 0.10 level). The optimum processing conditions were determined by response surface method, coupled with fuzzy synthetic evaluation algorithm, using membership trapezoidal function, with defined optimal interval values, depending on a final usage of dehydrated fruit. Practical Applications Osmotic dehydration (OD) of foods presents some advantages compared with common drying techniques, such as minimizing heat damage to the color and flavor, inhibiting enzymatic browning and reducing energy costs. The use of OD, as a complementary treatment in food processing, particularly prior to drying and freezing operations, reduces energy requirements of these processes. The technique aims to dehydrate food products by immersing them in hypertonic solution. The effects of different concentrations of sugar beet molasses (40–80%) and immersion times (1–5 h) on kinetics of mass transfer during OD/impregnation of apple cubes were studied. Sugar beet molasses as hypertonic solution is presented in this article because of high dry matter content and the enrichment of the food material in minerals and vitamins, which penetrate from molasses to the plant tissue. This investigation is also focused on finding the appropriate mathematical model for water loss, solid gain, sugars and minerals content, as well as change in colors and textural characteristics, during OD of apples in sugar beet molasses. The optimum processing conditions were determined by response surface method, coupled with fuzzy synthetic evaluation algorithm, using membership trapezoidal function, with defined optimal interval values, depending on a final usage of dehydrated fruit.