Infrared and hot-air drying of onions
2005
Kumar, D.G.P. | Hebbar, H.U. | Sukumar, D. | Ramesh, M.N.
The combination of infrared (IR) and hot-air drying of onion slices was explored, and the effects of processing conditions such as drying temperature, slice thickness, air temperature and velocity on onion slice characteristics were studied. The onion slice quality was evaluated on the basis of the color and the pyruvic acid content, an index of flavor. Drying of thin slices of onion (2 mm) at low temperature (60C) with a moderate air velocity (2 m/s) and air temperature (40C) retained greater flavor and color. An empiric equation developed to correlate the drying process variables and the onion slice moisture with the drying time provided a good fit (R2 = 0.92). Similar equations developed to correlate the drying process variables and the drying time with the pyruvic acid content provided an excellent fit (R2 = 0.96), while the equations fit for the total color change of onion slices were satisfactory (R2 = 0.86). Combination drying resulted in shorter drying process time and in better onion slice quality as compared to IR and hot-air drying applied individually.
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