The objective of the present investigation is the establishment of the appropriate techniques to improve the taste qualities of rice grown in the Hokkaido area by the application of the basic knowledge in the field of starch science. Results obtained are as follows: 1) Some physical and chemical methods for evaluating the taste qualities of rice, namely, the blue value method of Juliano, texturometer measurements and Brabender amylography, were modified and applied to the Hokkaido rice. The taste qualities of the Hokkaido rice are quite different from those of the Honshu (the Mainland of Japan) rice in the criteria such as pasting characteristics, retrogradation properties and amylose contents. 2) It was essential to put the better properties of gelatinization and retrogradation in the rice cultivar adapted to the Hakkaido area to improve the taste qualities of the rice. The author proposed that the development of the rice cultivar having the lower amylose contents and adapted to the area is the immediate importance as one of the approaches for quality improvements of the Hokkaido rice. 3) Amylose contents in the Hokkaido rice are influenced by the genetic backgrounds and the environmental conditions such as temperature during ripening period and supply of fertilizers. a) Amylose contents of rice grown at 23°C during all ripening period were 3.6% lower than those at 13°C by growth-cabinet experiments. Amylose contents were also affected by temperature in the night and in the, day during the ripening period, b) The blue value method is one of the effective methods to select individual rice from mother group. Because the method has good corelations to genetic variations. c) The taste qualities of rice were significantly inferior by deficiency of either phosphorus or potassium in the paddy fields. The qualities also tended to be lowered by increasing the amounts of nitrogenous fertilizer supplied.
