Cereal grains are a cheap and good source of energy and protein, which is an important ration in producing and developing countries. Rice is the only cereal which is just considered for human consumption and today with cultivation in more than 100 countries is as staple food for about a half of world population. In this study, the physical (length-breadth ratio, 1000-kernel weight, bulk density and hardness) and chemical (moisture, fat, total protein, fiber, starch and amylose content) properties of three Iranian native rice, Bakyan, Hashemi and Zayanderood were investigated. Moreover their cooking properties before storage, starch and protein properties were determined. finally textural properties and effect of aging were assessed. Results of physical and chemical tests indicated that Bakyan and Zayanderood classified in medium rice grain whereas Hashemi was categorized as a long rice grain. Hashemi had the highest hardness and the lowest bulk density. According to proximate analysis, Bakyan had higher moisture, fat, total protein and fiber content, whereas its starch and amylose content were lower in comparison with two other rice varieties. Hashemi and Zayanderood had the highest starch and amylose content, respectively. Observation of rice starches with scanning electron microscope (SEM) showed that rice starch granules were mainly polyhedral and their size ranged between 2.64 - 6.92 µm. The x-ray diffraction also exhibited that starch of three varieties had A type x-ray diffraction patterns. Study of other starch properties indicated that starch of Hashemi had lower light transmittance (%), syneresis (%) and swelling power, whereas its gelatinization temperature, turbidity and close packing concentration were higher in comparison with those of two other varieties. In respect to rice protein properties more than 70% of total protein of the varieties is glutelin. Alkaline extraction of proteins, resulted to protein isolates with about 90% putirty. Electrophoretic patterns of flour and protein isolates also revealed differences in several of bands. Results of cooking tests before and after aging (6 months in room temperature) indicated that Hashemi had lower elongation ratio and gruels solid loss whereas its cooked length-breadth and water uptake ratio were higher. Textural analysis of the cooked rice indicated that firmness, packability, maximum force, cohesiveness and chewiness were higher in Bakyan and lower in Hashemi. Generally, according to obtained results, Hashemi showed better properties before and after 6 month aging in comparison with two other rice varieties.
