Modification of rice-polisher machine to function as an appropriate sorghum grinding machine

Sorghum [Sorghum bicolor (L.) Moench] grain is prospectively used as an alternative foodstuff to substitute wheat which is progressively imported to Indonesia more than 11 million tons per year. A common problem faced in the utilization of sorghum grains domestically is the lack of equipment for the polishing process before the grains are ready to be used as foodstuff. Polishing is necessary to remove the tannin content contained in the pericarp layer and tightly fused with the endosperm. The tannin content causes a bitter and astringent taste that is not liked by consumers. Tannin can also reduce protein digestibility and cause constipation. This study purposed to design and modify the rice polishing machine into a sorghum grain polishing machine that can operate continuously and has a high capacity with good quality polished sorghum grains. An appropriate polishing machine is needed on a small scale that is user-friendly for the villager processor. The modification of the common rice polishing machine was conducted to fulfill the need. The rice polishing cylinder is made of cast iron and is equipped with two air distribution grooves along the cylinder which can blow the rice bran. Modifications are made by dividing the polishing cylinder into three parts. The centerpiece, cast iron was replaced by a grindstone that grooved along and around the cylinder for air distribution as well as ground pericarp transporter. The improved polisher machine could treat the sorghum grains continuously with polishing capacity of 100-120 kg/hour, and an average yield of 85 %.