Quality Evaluation of Onion Slices Dried Using Low Pressure Superheated Steam and Vacuum Drying
2017
Rachna Sehrawat | Prabhat K. Nema | Pitam Chandra
The effect of combined low pressure superheated steam drying (LPSSD) followed by vacuum drying (VD) on quality of onion slices at different temperature (60-80 o C~10 kPa) was determined. In the first stage, the moisture content of onion slices was reduced to 50 % (w.b.) from 88-90 % (w.b.) using LPSSD; and then it was further reduced up to 7-8 % (w.b.) by VD. It was found that among the various drying temperatures studied, retention of colour, rehydration ratio, thio-sulphinate content and antioxidant capacity of dehydrated onion was better at 60 o C, followed by 70 o C, whereas total phenol contents were higher at 80 o C. The results of control dried sample and sample dried at 60 o C had significant differences in time taken for drying, thio-sulfinate content, total phenol content and antioxidant capacity, whereas insignificant effects of drying temperature was observed on rehydration and water activity of dried onion slices.
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