Studies on the Relation between the Types of Soil and the Palatability of Paddy Rice : II. On the relation between chemical characters of rice grains and taste of cooked rice

[摘要] Paddy rice was cultivated on several types of soil, and the relation between the taste and physicochemical properties of rice grains were studied. the results are summarized as follows. Peat soil and severely lodged plants grown on diluvial soil produced rice grains low in starch content and also those grains were low in alkali resistance. Owing to these characters of rice grains the gelatinization upon cooking was depressed and resulted in inferior taste of boiled rice. These properties of rice grains are considered to be resulted by the over-luxuriant growth caused by excess nitrogen in later stage of the growth of the rice plants as reported in the previous paper. Alluvial and tertiary soil on the contrary produced rice grains with high starch content and high alkali resistance and cooked rice showed good palatability. The lodged plants on diluvial soil produced rice grains high in total nitrogen and proteins, and the latter might have induced the collapse of outer layer and promoted the depression of softening of inner layer at cooking. The rice grains prduced on peat soil was next to the lodged rice grown on diluvial soil in the amount of globulin and had cosiderable amounts of other proteins. Owing to these characters, the rice grains grown on the peat soil showed depression of the amounts of dissolved materials and swelling at cooking under higher temperature and ultimately became inferior in softness. The rice grains prduced on alluvial soil was poor in their nitrogen content and the amounts of dissolved materials at low cooking temperature was high and both the high amounts of dissolved materials and good swelling at high cooking temperature resulted in the high softnese of the cooked rice. The rice grains on tertiary soil was high in proteins other than globulin and proved to be gelatinized easily in cooking at high temperature. As to the effect of nitrogen, the cases of lodged plants and rice grown on peat soil, the proteins especially globulin in rice grains appeared ot depress the amounts of dissolved materials and swelling. Globulin might do so more severely at higher temperature. The rice grains produced on volcano ash soil was deficient in phosphate especially in rice bran, and both starch content and alkali resistance were low, the depression of dissolved material and swelling in cooking were found to occur ultimately resulting to the considerably inferior in taste. In these rice grains, the mal-effects of proteins at cooking as stated above was probably negligible because of the low content of total nitrogen and globulin. The main factors of rice grains produced on different types of soils to be cooked soft, sticky and palatable are considered to be the content and alkali resistance of starch, and high content of proteins especially that of globulin might promote the inferiority of boiled rice. Amylose contents had little influence in these cases.

[学科分类] 农业科学（综合）