Pulsed Vacuum Osmotic Dehydration of Garlic Bulbs Followed by Microwave Drying

The combination of pulsed vacuum osmotic dehydration and microwave drying of garlic bulbs were examined. The response surface methodology (RSM) was used to determine the effect of NaCl concentration (8%-20%), osmotic solution temperature (25-65°C), operation pressure (240-830 mbar), immersion time (20-300 min) and microwave power level (100-600 W) on water loss (WL), solids gain (SG), weight reduction (WR), hardness and shrinkage of samples. Analysis of the results showed that by increasing the osmotic solution concentration, temperature and immersion time, WL and WR will increase. The effect on SG was almost the same as WL except the effect of temperature. Increasing temperature resulted in an initial increase in SG for a period of time, followed by a decrease. NaCl concentration, temperature and immersion time showed the significant influence on hardness.