yoshimitsu katoh

The qualities and cooking characteristics of wash free produced by the medium method and dry method, that is, (1) The weight of wash free rice is little less, and the white degree is higher than those of usual milled rice. Comparing medium method to dry method, the white degree of the latter is lower, and the ratio of protein and fat is little higher. (2) On examining the turbidity of washing liquid, the pureness of two kinds of wash free rice by medium method are higher, and the damage of rice grains is less than those by dry method. (3) The observation of the steamed rice surface with an optical-microscope shows that the steamed wash free rice produced by dry method makes the fat quality darken by zudan stained color, which proves that, much white rice bran and others remains. (4) Sensory evaluation was performed, wash free rice left over for one day, has lower stickiness, lower palate, and lower evaluation in overall than usual milled rice, which shows significant difference.

Cooked rice boiled in hard water is considered to be harder than when boiled in soft water. In order to clarify this phenomenon, the visco-elastic and morphological properties were compared between rice grains cooked in water with and without calcium ions. The calcium concentration used for the Ca rice was 0.05 M of calcium lactate. Texturometric measurements indicated the hardness of the Ca rice to be significantly higher (20%) than that of the non-Ca rice. The averaged sizes of both the Ca rice grains and the endosperm cells were statistically smaller than those of the non-Ca rice from microscopic measurements. A histochemical comparison was carried out on the sections of cooked rice grains, focusing on the localization of proteins, pectin and Ca ions. Protein, pectin and calcium in the non-Ca rice were mostly localized in the endosperm cell wall forming the surface layer of the rice grain, being sparsely distributed at the center of the grain. Calcium was present in the locci of Ca rice containing protein and pectin and in the starch granules within. It is considered that the hardness of Ca rice was due to the prevention of swelling of the rice grains, thus reducing the water absorption, which may have been caused by interaction of the calcium and calcium-binding components such as proteins and pectin in the endosperm cells and starch granules.