ACCELERATED PARTIAL DRYING AND STERILIZATION OF HIGH MOISTURE ROUGH RICE

Document Type : Original Article

Authors

1 Agricultural Engineering Research Institute, Agricultural Research Center, Dokki, Giza, Egypt

2 Professor of Agricultural Engineering, Faculty of Agriculture, Mansoura University, Mansoura, Egypt

Abstract

A study was carried out to evaluate the effectiveness of high temperature-short time conduction heating for accelerated partial drying and sterilization of high moisture rough rice (Giza 176). Experimental rotary heating unit was specifically designed and constructed at the workshop of Agric. Mech. Dept. Fac. of Agric. Mansoura Univ., to provide heating surface temperatures of 75, 100, 125 and 150°C, exposure time of 2,3,6,8,10 and 12 mins., cylinder rotational speed of 5. 10 and 15 r.p.m., and grain feed rate of 1.5, 2.5 and 3.5 kg/pitch. Rapid moisture removal from rough rice existed during high temperature, short time conduction heating process. The moisture removal rate was found to be dependent upon heating surface temperature, exposure time, and grain feed rate. High temperature short time conduction heating also distinctly reduced fungal activity in rough rice. Quality evaluation tests of milled rice showed an increase in head rice yield accompanied by a reduction in milled rice whiteness. Heat treatment of rough rice corresponding to a fungal mortality level of 75-80% led to a maximum head rice yield and acceptable .level of reduction in whiteness of milled rice. Mathematical models were developed to predict the moisture content and other quality changes of grain during conduction heating process. These models may be used in any further studies aiming to develop a full-scale conduction heating rotary dryer.

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