Effect of Moisture Content on Physical and Mechanical Properties of East Java Local Unhulled Rice Varieties. Darmanto(a), Andri Paska Ginting(a), La Choviya Hawa(a), Sandra(a*)
(a) Agricultural and Biosystem Engineering,Universitas Brawijaya
*sandra.msutan[at]ub.ac.id
Abstract
The purpose of this study is to obtain physical and mechanical properties of some East Java local unhulled rice as well as its quality based on Standard Nasional Indonesia (SNI). The properties measurement comprised geometrical dimension, gravimetric property, density, static friction coefficient, compressive strength, compressive strain, and elastic modulus. The local unhulled rice varieties were cempo rogo, mahameru, glutinous rice mentok Ponorogo. The research method used was an experimental method by conditioning the moisture content of the unhulled rice with the addition of water then measured and tested its physical and mechanical properties, calculated the percentage of grain milled, and according to the variation in the moisture content determined by 3 repetitions of each treatment. The results of this study were that the geometrical properties, such as average diameter, surface area, volume, and roundness, increased with increasing water content around 0,8-0,9 mm- 0,6-0,9 mm2- 0,7-0,9 mm3- and 0,6-0,8 %, respectively. For gravimetric properties, measurement of the mass per 1000 seeds resulted increasing 0,9 gram mass. The average bulk density increasing was around 0.7-0.9 gram/cm2, the true density tended to increase around 0.01- 0.9 gram/cm2, while the pororsity tend to decrese with the water content increasing around 0,8-0,9 %. Frictional properties (bulk angle and static friction coefficient) tended to decrease with increasing water content which was influenced by the level of hardness on the plywood, iron plate, and glass skirting boards of 0.8-1o and 0.8-0.9o, respectively. The mechanical properties in the form of compressive strength tended to drop with water content rising at range 1,39 - 2,23 N/mm2, however the strain increased at range 0,059 - 0,2. The milling results showed that the percentage of headed rice was still up to SNI grade with water content increasing which is 25,6 - 65,5 %, however broken and groats rice were out of SNI grade.
Keywords: Unhulled rice, mechanical properties, physical properties, East Java, SNI
