Onion slices were dried under different processing conditions by hot air dryer. Slice thickness, air velocity were constant and inlet air temperature, drying time were varied to study the drying behavior. Thin layer drying of onion slices was carried out at air temperatures of 60, 70, 80 and 90 C ° and air velocity of s m 5 . 1 . The drying occurred in the falling rate of drying period. 13 available moisture ratio models were fitted to the drying data. The model proposed in this study had a higher squared correlation coefficient ( 2 R ), and low sum of square error ( SSE ) and thus predicted drying behaviour of the onion slices more accurately. The average effective moisture diffusivity of onion slices ranged between 1 2 10 10 125821 . 0 - - ´ s m and 1 2 10 10 788957 . 0 - - ´ s m . The values for eff D increased with a increase in air temperature and decrease in moisture content under all drying conditions.

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