Influence of Temperature on Drying Kinetics of Aloe Vera During Osmo-Conveytive Dehydration

Abstract

The present study was carried out to investigate the mass transfer kinetics of Aloe Vera gel cubes during osmo-convective and convective drying and its quality evaluation. Aloe Vera leaves were washed and cut into 25 x 25 x 25 mm cubes and were osmotically dehydrated in different concentration (43.2, 50, 60, 70, 76.8°Brix) and process temperature (43.2, 50, 60, 70, 76.8°C) with syrup to gel ratio (4.3:1, 5:1,6:1,7:1, 7.7:1) for 4 hr duration of osmosis. Central Composite Rotatable Design was used to analyse osmotic dehydration process. The osmosed and untreated Aloe Vera gel cubes were dried in tray dryer at 50°C, 60°C, 70°C and hot air dryer at 60°C, 70°C, 80°C. The effect of osmosis, sugar concentration and process temperature of syrup on mass reduction, water loss and sugar gain were studied during osmotic dehydration. It was found that mass reduction, water loss increased with increase of sugar concentration and process temperature while solid gain decreased with increase in sugar concentration and process temperature. It was found that osmosis as a pretreatment prior to convective air drying was able to decrease drying time. It was observed that drying rate increased with increase in drying temperature from 50°C (Tray drying) to 80°C (Hot air dryer) and constant rate drying period was absent throughout the drying process of Aloe Vera cubes dried under all drying air temperatures. The osmo-convective dehydrated samples were found more acceptable than convective dried ones. Air temperature and pretreatment as osmotic dehydration had a significant effect on sensory evaluation.