OSMO-Convective Drying of Onion Slices
- 1 Dept. of Processing and food Eng., College of Technology and Eng. Maharana Pratap Uni. of Agriculture and Tech. Udaipur, INDIA
Res. J. Recent Sci., Volume 1, Issue (1), Pages 51-59, January,2 (2012)
The present study is carried out to standardize the pretreatment of onion slices and study drying characteristics during convective drying. The effect of process parameters during osmotic dehydration such as osmosis, concentration and temperature of syrup on mass reduction, water loss and salt gain increased with increase of syrup concentration and temperature. The water loss and solid gain during osmosis at 5, 12.5 and 20 \rBrix was varied in the range of 15.88 to 25.65 and 6.63 to 10.15 per cent at 35, 45 and 55\r C temperatures respectively. The drying temperature and pretreatment as osmotic dehydration had a significant effect on the rehydration ratio and colour. The drying times of un-osmoses and osmoses onion slices by convective drying at 40 and 60 per cent drying temperature were 12, 10 and 8 and 6 hrs respectively. Quality of dried product in respect to colour and rehydration was superior. The osmo-convective dehydrated samples were found more acceptable than convective dried ones. The onion dried at 20\rC brix solution concentration, 55\rC osmosis temperature and 70°C drying temperature was more acceptable on the basis of colour and rehydration.
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