In Thailand, trading price of rough rice depends on a total amount of Head Rice Yield (HRY), evaluated by the buyer using a laboratory rice milling machine.
It was noted that the HRY trended to reduce when performed several consecutive milling tests. The aim of this research is to investigate the effective of screen-slot angles effect of milling machine on obtaining RD 31 head rice yield, and to understand the effect of associated grain temperature on head rice yield. Results show that the screen slot angle effect the head rice yield, and the optimum HRY obtained is between at the screen slot angle of 45 degree. The HRY decreased significantly after performing three consecutive tests. The accumulated heat on the milling cylinder tend to increase grain temperature and lead to lower HRY.