Abstract:

Osmotic dehydration is a pre-treatment used for partial removal of water from food materials and inhibits the loss of sensory and nutritional attributes of dried food. The main drawback of osmotic dehydration is the solutes uptake of food material from the hypertonic solution. Optimization of process parameters is critical to achieve desired levels of dehydration and solid uptake. To minimize the solid gain, food materials are coated with edible films prior to drying. In this study, the effects of solution temperature (25°C, 35°C and 45°C), sugar solution concentration (40%, 50% and 60%) and edible film coatings on solid gain (SG) and water loss (WL) of osmotically dehydrated carrot slices were investigated. Solid gain and water loss rates after osmotic dehydration were determined and dehydration efficiency index values were calculated. It is observed that WL and SG values increase with the increasing temperature and solution concentration. The solid permeability of cornstarch coating was lower compared to plum coated and non-coated samples. Weight loss of dehydrated carrot slices coated with cornstarch were higher than the non-coated ones. Cornstarch based edible coatings did not have a negative effect on water loss while plum based edible coatings caused the water loss to decrease. Optimum mass transfer rates for water and solids were achieved at 25°C with a solution concentration of 60%. Highest dehydration efficiencies recorded were of starch-coated samples at all process parameters. Plum coating showed a slight improvement against non-coated samples at optimum process parameters.

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