Figure 1 Schematic demonstration of osmotic dehydration process(Lewicki and Lenart, 1995) Lenart (1996) deduced four main advantages of using osmotic dehydration:
1. Reduction of heat usage, hence negative changes of color and aromatic substances are diminished in subsequent drying.
2. The cell membranes are not absolutely resistant to osmotic substance, assuring a small flow of sugar into the cell, causing a sweeter taste of the dehydrated food.
3. Osmotic dehydration as a pretreatment provides shorter drying time and increases the dryer's potential.
4. Energy consumption is smaller at a rate of 20-30 % when compared to convective drying.
Bhupinder singh et al.(2013) optimized osmotic dehydration of beetroot candy by response surface methodology, the experiments were conducted according to Central Composite Rotatable Design (CCRD) with three variables at five levels. The low and high levels of the variables were 35 and 55○C for osmotic solution temperature, 30 and 60○Brix for sucrose solution concentration, 30 and 180 min for duration of dipping in osmotic solution, respectively. The fruit to solution ratio was kept 1:4 (w ⁄ w) during all the experiments. The optimum conditions for osmotic solution concentration, temperature and process duration were 60oBx, 55oC and 180 min, respectively.