Effect of combined pulsed vacuum osmotic dehydration- hot air drying of Orange slices by response surface methodology

Osmotic dehydration is a viable process for the partial removal of water fromplant tissues such as fruits and vegetables. The main advantage of this process is itsinfluence on the principal drying method, shortening of the drying process, resultingin lower energy requirement. Considering that heat is not applied in this stage.Osmotic dehydration offers higher retention of initial food characteristics, such ascolor, aroma, nutritional constituents, and flavor compounds. The effects oftemperature and concentration of osmotic solution 30-55 ºC and 40-60% (w/w),respectively, Contact time 120-300 min and by applying vacuum pulse (100-300mbar for 10 min) at the beginning of the process (pulsed vacuum osmoticdehydration, PVOD) and Drying temperature (40-70 ºC) on color changes and WL(water loss) to SG (solid gain) ratio of orange slices were studied. The optimizationof combined process was done by Response surface methodology with Centralcomposite design. The analysis of variance showed that a linear model predicted wellthe experimental data. The applied temperature of osmotic solution and dryingtemperature had the main effect on responses. Optimization conditions were basedon the higher water loss to solid gain ratio and lower changes of color. Optimalconditions were 35 ºC for osmotic temperature, 60% for sucrose concentration, 180min for osmotic time, 240 mbar for pressure and 41.5 ºC for drying temperature.