In spite of good aroma and flavor of cooked rice for common rice varieties in Isfahan province they have excessive breakage losses, qualitatively. So, the knowledge of effective parameters on these losses is vitally important. In this research the main quality assessment parameters of rice milling including head rice yield (HRY) and degree of milling (DOM) were determined from milling experiments. The experiment were conducted for common rice varieties in Isfahan as Sazandegi, Nogaran and Sorkheh at different moisture contents (MC) of 7-9, 9-11, 11-13 and 13-15% w.b. by two laboratory rice miller types: abrasive and frictional. As the inherent properties of kernel could affect HRY and DOM values, some physical and mechanical properties were determined as well. The physical properties included size and shape for rough rice and coefficient of external friction for brown rice. The mechanical properties were rupture force, rupture energy, specific rupture energy and maximum bending stress. The experiments were carried out with factorial layout in completely randomized design. The independent variables were variety type, rice miller type and MC. To determine HRY and DOM first the selected rough rice sample for each treatment was dried in a fixed bed dryer at three replications and then was husked and whitened by a rubber roll husker and two rice miler types, respectively. HRY was computed through USDA standard procedures and DOM was determined by two methods: 1) a milling meter (DOM MM ) and 2) the amount of bran removed from the brown rice (DOM M ). Two compound indexes were defined by multiplication of HRY and two degree of milling (C.I M and C.I MM respectively by HRY and DOM M and HRY and DOM MM ). Three main dimensions, equivalent diameter and sphericity were measured at 100 repetitions for each treatment and external coefficient of friction of brown rice was measured on four different surfaces at 3 replications. Mechanical properties experiments were conducted by three point bending test performed by a universal tension-compression test device model instron 1140 at 10 replications for each treatment. The desired characteristics were determined and computed from force-displacement curve. The results indicated that the rice miller type had a significant effect on HRY, DOM M , DOM MM , C.I M and C.I MM. According to the investigated parameters the abrasive type had a better performance than frictional type. The effect of variety type on HRY and DOM and all physical and mechanical properties was significant. HRY decreased by increasing MC but DOM showed no obvious trend. Except for major diameter the MC affected all other physical properties significantly, so the intermediate and minor diameters, sphe
