A b s t r a c t. The present investigation deals with analyzing the compressive strength properties of two varieties (Tarom and Fajr) of parboiled paddy and milled rice including: ultimate stress, modulus of elasticity, rupture force and rupture energy. Combined artificial neural network and genetic algorithm were also applied to model these properties. The parboiled samples were prepared with three soaking temperatures (25, 50 and 75°C) and three steaming times (10, 15 and 20 min). The samples were then dried to final moisture contents of 8, 10 and 12% (w.b.). In general, Tarom variety had higher compressive strength properties for paddy and milled rice than Fajr variety. With increase in steaming time from 10 to 20 min, all mentioned properties increased significantly, whereas these properties were decreased with increasing moisture content from 8 to 12% (w.b.). Coupled artificial neural network and genetic algorithm model with one hidden layer, three inputs (soaking temperature, steaming time and moisture content), was developed to predict the compressive strength properties as model outputs. Results indicated that this model could predict these properties with high correlation and low mean squared error.K e y w o r d s: artificial neural network, genetic algorithm, paddy, milled rice INTRODUCTION Rice (Oryza sativa L.) is the principal food cereal in the world and it is the main food of over half of the world population (Razavi and Farahmandfar, 2008). The majority of Iranian rice (75%) is grown in Mazandaran and Guilan provinces (Zareiforoush et al., 2010). The production rate is still far from the country rice self-sufficiency. Increasing the grain severity and hence reducing the processing losses could be a possible way of compenzation for the increasing demand. The primary step in rice processing is dehusking of paddy, which results in brown rice. Polishing or removing of bran to yield white rice is the second step. Knowledge of the compressive strength properties of rice is important in the design of milling equipment to predict their cracking behaviour and to minimize the losses during handling, drying, cleaning and milling processes. For this reason, extensive studies have been done in this area, that would be reviewed here. Shitanda et al. (2001) explored the physical and mechanical properties of paddy and rice. They showed that shortgrain rice was harder than long-grain variety and had less broken grain. They noted that husking characteristics of rice are related to shape and size of rice. Cao et al. (2004) explored the effect of moisture content on some mechanical properties of brown rice. They showed that moisture content has a significant effect on mechanical properties ie compressive strength and tensile strength decreased with increasing moisture content. Corrêa et al. (2007) explored mechanical behaviour of grains in rice processing. They showed that compressive force was significantly affected by processing. Zareiforoush et al. (2010) investigated the mechanical properties of two rice varieti...