Studies on the Scented Rice : III. On the differences in the Cooking Behavior of Rice according to Grain Texures (1967)

Nagato And Kono have experimented the Changes in the distribution of hardness of rice of various types (Type Ia, Type IIc, Type IId, and Type IIe) according to starch cellular tissues. We also attempted, by using the samples cited below, to clarify the differences in the process of cooking the brown and white rice of Types I and II by heating over hot water of by heating with ordinary cooking methods. In order to find out the changes of sample rice into cooked rice, authors took microphotographs of 28 magnifications by employing the so-called "Sump" printing method. Test samples: Type Ia: Foreign rice variety (Denurado) Type IIc: Domestic semi-soft rice varieties (Norin No. 22, Honen-wase) Type IId: Domestic soft rice variety (Otsune-bozu, a scented rice) Type IIe: Domestic ultra-soft rice varieties (Karasu and Hieri) Test results: (1) In both cases of brown rice and white rice, Type Ia rice was slowest in cooking when cooked by heating, and Type II group rice were quick in cooking in the order of Type IIc, Type IId and Type IIe. When cooked in an electric rice cooker prevailing now widely in the country, the standard time for cooking regular white rice showed somewhat shorter for cooking Type Ia rice, while too longer for cooking Type IIe rice. (2) Even in the cases of rice of rice of the same type, the changes of brown rice into cooked rice by heating over hot water were not always coincident with the changes of white rice by heating with ordinary cooking methods. Particularly great disparity in the changes was found in the case of Type IIe white rice. Namely, by 20 minutes' heating, the changes in Type IIe white rice took place more slowly or as quickly as the changes in Type Ia or Type IIc rice, but by 30 minutes' heating-immediately before completion of cooking-the changes of white rice to become pasty and swollen took place quickly in particular, while in the case of brown rice, the aforesaid distinction could not be found clearly. (3) Type Ia foreign rice variety began to become pasty and swollen from the peripheral part of grains, but in the case of cell groups which have developed fully in ever part. most of them remained still unswollen. (4) Grains of Types IIc and IId rice began to become pasty and swollen from their peripheral parts followed by these parts in the order: starch cells along the longitudinal line (running through the back and abdominal parts), the central parts of grains, and the middle parts of grains making a right angle with the longitudinal line; thus, completing the cooking process. (5) In the case of Type IIe ultra-soft rice varieties, particularly some scented rice, at the beginning of cooking process by heating, the changes took place as quickly as or rather little more slowly than the changes in Type Ia and Type IIc rice, but after that the former changed into cooked rice very quickly, and that the grains of the former burst open in every direction just like a popcorn, though those of the latter stretched out only. From the above test results, it can be concluded that the changes in the distribution of hardness of each type of rice according to starch cellular tissues found by Nagato and Kono coincided well with the differences in the process of cooking white rice we found out.