Performance Evaluation of Two Rice Milling Machines under Different Moisture Contents and Rice Parboiling

Abstract

Rice is one of the cereal crops which recently contributed as a food source in Sudan after sorghum, millet and wheat. Rice production is very important to fill the gap of food consumption. The objective of this study was to evaluate the performance of a steel miller and a rubber rolls husker rice milling machines under three rice grains moisture content levels (16 %, 14 % and 12 %) and parboiled rice at 12% moisture content. This experiment was conducted in the White Nile State, Kosti town, during season 2017/2018; local rice variety (misry) was used in this research. The experimental design was a split plot, whereby the rice moisture content constituted the main plot, while the type of milling machine constituted the sub plot. The data collected were used to compute milling recovery, head rice yield, broken rice and milling (polishing) degree. These parameters were statistically analyzed by GenStat12 software program. The results of the milling rice recovery showed highly significant differences (P≤0.01) between the two milling machines and rice moisture contents. The highest milling rice recovery was 63% for the steel miller at 12 % rice moisture content and 68.1% with parboiling, while it was 62% for the rubber rolls husker with parboiling. The results obtained for head rice yield indicated highly significant differences (P≤0.01) between the two milling machines and rice moisture contents. The highest head rice yield was 83% for the steel miller and 86% for the rubber rolls husker with parboiling. Furthermore, the results of broken rice showed highly significant differences (P≤0.01) between all treatments whereby the lowest amount of broken rice was 19% for the steel miller and 14% for the rubber rolls husker with parboiling. The results for milling degree showed significant differences (P≤0.05) between the two machines and rice moisture contents, whereby, the highest milling degree was recorded by the steel miller with 12% rice moisture content (13.3%) and with parboiling (13.2%), while the lowest milling degree was recorded by the rubber rolls husker with parboiling rice (0.9%). It is recommended to use the steel miller machine for husking rice at 12% moisture content and parboiling.