Rice is the second most important agricultural crops. Because about one third of the world population depend on it as one staple food. Due to the necessity of self-sufficiency in rice production, reducing losses during milling process of rough rice into white rice is of great importance. Rice is commonly harvested at high moisture contents (MCs) (25 to 35 %w.b.). To perform the milling process and prevent product deterioration during storage, it is required to reduce the initial MC. One of the factors affecting the quality of rice during milling is internal fissured kernels created during and after the drying operation. The fissures reduced the resistance of the kernel to failure significantly. During drying, the outer surfaces of the kernels obtain MCs less than those for inner parts. This difference in MC between various parts of the kernel is caused internal MC gradients. Moisture gradients within the grain caused tensile stresses at the surface and compressive stresses at the center of a kernel, which in turn cause fissures to develop when the amount of stresses exceeds the strength of the rice kernel. Under intermittent drying method; in order to subside the moisture gradients within the kernel, after each drying pass the rough rice is kept in a place at a certain temperature for certain durations so that the moisture is not allowed to transfer into the medium (closed jar). This process is called tempering. The mechanical and thermal properties of a rough rice kernel undergo major changes provided the kernel goes through a glass transition (crossing the glass transition temperature (T g ) line) due to its temperature and MC changes. At a temperature and MC below the T g line, starch exists as a glassy material. As the kernel passes the T g line, the starch goes from a glassy into a rubbery state and vice versa. Since this state transition occurs in the temperature ranges typically happened during rice drying, determination of T g line for rough rice varieties, and simulation of intermittent drying kinetics is vitally important in order to predict the kernel behavior and obtain the optimal conditions for drying and tempering operations. In this study the state diagram (T g variations with MC) was obtained for Hashemi (long grain) rough rice variety. The T g values at five MCs were measured by differential scanning calorimeter (DSC) method. Moreover, the effect of intermittent drying process on fissuring of Hashemi and Koohsar (medium grain) varieties was investigated. The number of fissured kernels having one, two and more than two fissures was determined in 100 kernels, immediately after the end as well as 48 h after drying process. Then, an index namely, stress cracks index (SCI) was accordingly computed. The optimal durations and temperatures for drying and tempering processes were determined using the experimental results and analysis of MC distributions within a rice kernel by a simpli?ed sphere drying model. A hot air convective dryer equipped with relative humidity and temperature control systems was used to conduct the experiments. The experiments were performed under thin layer drying mode at relative humidity of 40% and air velocity of 0.5 m s -1 with two replications. In one case, the experiments were carried out at drying and tempering temperatures of 30, 45 and 60 °C, drying durations of 20, 40 and 60 min, and constant tempering duration of 80 min. In order to investigate the influence of drying and tempering durations on kernel fissuring, the second case of the tests were also performed at constant drying and tempering temperature of 60 °C, drying durations of 20, 40 and 60 min, and tempering durations of 0 (continuous drying), 40, 80, 120, 160, 200, 240 min. The continuous drying condition (no tempering) was modeled by fitting the experimental moisture ratio data to 12 well known empirical models. According to the maximum coefficient of determination (R 2 ) and the minimum root mean square of error (RMSE), the Verma et al . (2007) model showed the most accurate results. The simpli?ed sphere drying model was capable of accurately simulating the drying and tempering processes of rough rice. The T g was linearly decreased with increasing the MC. It was also revealed that changing from glassy to rubbery state of Hashemi rough rice occurs in the temperature range which is commonly applied for drying this variety. The SCI for Hashemi variety was less than that for Koohsar variety. The SCI increased and the drying time decreased as the drying temperature.increased. Moreover, the SCI increased with increasing drying time for all drying conditions. However, the rate of this increase was the highest at 60 °C. Both the total operation time and the SCI decreased when the tempering temperature increased.