Effect of process parameters on the effectiveness of osmotic dehydration of summer onion

The present study was carried out to investigate the effects of solution concentration, immersion time and temperature on the osmotic dehydration (OD) of summer onion. OD was done using sucrose, salt and combined (sucrose-salt) solution. In this study three sucrose (40,50 and 60%), five salt (5,10,15,20 and 25%) and five sucrose- salt (combine) solution (40:15, 45:15, 45:20 50:15 and 55:15 %) were used. Among different solution concentration and temperature for 6 hrs contact time 55:15°brix at 40°C gave water loss (50.05%), solid gain (16.25%) and normalized solid content (2.34), while 60 °brix sucrose solution gave 35.60%, 9.32%, 1.81 and 25°brix salt solution gave 33.50%, 12.21%, 2.25 water loss, solid gain and normalized solid content respectively. It was also found that at ambient temperature (25°C) 55:15°brix for 24 hrs contact time gave the highest water loss (56%) and solid gain (17.80%). It can be concluded from this study that solution temperature, time and concentration were the most pronounced factors affecting solid gain, water loss and normalized solid content of onion slice during osmotic dehydration.