Effect of tropical environmental conditions on rice kernel breakage during milling
1991
Noomhorn, A. | Yabai, C.
The effect of tropical environmental conditions on rice breakage during milling was studied. Long grain rough rice (Oryza sativa L) of Suphan-60 variety from Thailand was freshly harvested at 22.5% moisture content (wet basis), threshed in the field and subsequently dried by aeration in a flat bed grain dryer to 14% moisture content. About 200 g of previously cleaned, well mixed samples were placed in moisture-free polyethylene bags and stored temporarily in cooling chambers (4-5 degrees C). Rough rice samples were subjected to environmental conditions of 20-35 degrees C and relative humidity of 40-90% during milling. The results indicated that the head rice yield decreased with increase in milling environment temperature at different relative humidity conditions. Head rice yield decreased by approximately 3.51%, 1.26% and 1.65% for increased temperature of 20-35 degrees C at 40%, 60% and 80% relative humidities, respectively. Furthermore, the results also showed that the highest head rice yields of 55.30 to 56.01% were obtained at 70-80% relative humidities and in the 20-25 degrees C temperature range. The effect of tempering on rice kernel breakage during the milling process was also studied. The results showed that during tempering treatment kernel temperature rise during milling was reduced by 2.2 degrees C and 2.87 degrees C for two and three passes, respectively. A head rice yield increase of 0.95 to 1.12% was observed during the tempering process. Increasing the number of passes from one to three during milling results in a lower kernel temperature rise and a higher yield of 2.08 and 1.30% for with and without tempering, respectively.
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