Drying characteristics and milling quality aspects of paddy dried with gas-fired infrared
2009
LAOHAVANICH, JUCKAMAS | WONGPICHET, SEREE
Wet paddy was dried under different process conditions applying a laboratory gas-fired infrared (GIR) dryer. Peak wavelength of infrared emitted and initial moisture content of paddy were varied to study the drying behavior. The available thin-layer drying models were fitted to the drying data. Then, the modified Page model was chosen with higher coefficient of determination (R² = 0.9985 - 0.9695) and best-fitted over other models, based on comparing the values of root mean square deviation (RMSD), average percentage of error (%E) and chi-square (χ²) between the observed and predicted moisture ratios. Qualities of GIR and temper-dried wet paddy in terms of head rice yield and whiteness were evaluated. Response surface methodology found that an increase in GIR drying time could increase head rice yield. However, an increase in both GIR drying time and tempering time could decrease the whiteness. The contour overlay graph could then be used for determining the appropriate drying conditions, depending on the industrial or user requirement. Infrared (IR) drying technology has appeared as one of the potential alternatives to the traditional heating methods for obtaining high-quality dried agro-products. For long-grain paddy drying, there is at present a dearth of reports exploring IR drying kinetics, and even in such reports, milling quality was the focus of investigation with respect to appropriate drying process conditions. This study has presented the modeling determination and explanation on milling qualities of paddy dried with gas-fired infrared dryer. The drying process has provided a guideline on basic information to build a commercial drying system. Finally, these results would have practical applications for maintaining or increasing the milling qualities of paddy in the existing industry.
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