Positional Differences in Swelling Degree, Gelatinization Temperature, and Protein Content of Rice Flour from Large and Small Rice Grains

摘要

The swelling degree, gelatinization temperature, and protein content of rice flour prepared from the ventral and dorsal parts of rice grains used for sake brewing (large grains) and staple food (small grains) were examined. The swelling degree of rice flour was higher in the order: ventral part of large grains ? ventral part of small grains > dorsal part of large grains ~ dorsal part of small grains. The rice flour obtained from the ventral part of large grains also exhibited the highest swelling power, lowest gelatinization temperature, and lowest protein content. The white precipitate remaining after the measurement of swelling power was subjected to iodine and Berlin blue reactions and observed microscopically. From these findings, we speculate that rice flour containing large amounts of protein may be difficult to gelatinize because protein firmly adheres to starch, resulting in reduced water absorption and consequently, reduced gelatinization.