A Superheated-Steam Fluidized-Bed Dryer for Parboiled Rice: Testing of a Pilot-Scale and Mathematical Model Development

Abstract

This article describes the testing of a pilot-scale superheated-steam fluidized-bed dryer for parboiled rice along with development of a mathematical model for predicting the changes in temperature of steam and moisture content of parboiled rice during drying. Based on the obtained results, it was found that the superficial velocity of steam from 1.3 to 1.5 times of the minimum fluidization velocity had no significant effect on the drying rates of rice. The energy consumption for reducing the moisture content of paddy from 0.43 to 0.22 kg/kg dry basis was approximately 7.2 MJ/kg water evaporated. Drying temperature caused the appreciable change of parboiled rice qualities as characterized by water adsorption, whiteness and pasting viscosities, white belly, and hardness. Soaking paddy at a temperature of 70°C for 7–8 h before drying was sufficiently enough for producing parboiled rice, with no white belly. The gelatinization of starch during drying resulted in higher head rice yield of the product as compared to that of raw paddy.

Keywords:

• Fluidization
• Gelatinization
• Parboiling
• Simulation
• Starch

ACKNOWLEDGMENTS

The authors express their sincere appreciation to the Thailand Research Fund for financial support. Thanks are also due to the Pathum Thani Rice Research Center for testing physical qualities of rice and to the Institute of Food Research and Product Development, Kasetsart University for allowing the RVA test.

Notes

Note: Same letters in the same column indicate that values are insignificantly different at p < 0.05.

*Chalky grain.

Note: Same letters in the same column indicate that values are insignificantly different at p < 0.05.

*Chalky grain.