1996 Volume 91 Issue 7 Pages 515-520
Water-absorption capacity of rice grains was strongly affected by content of amylose, white-core and white-belly, respectively. The content of amylose affected the maximum water-absorption capacity of rice grains. On the other hand, both white-core and white-belly affected mainly absorption rate of rice grains. In ordor to elucidate the cause of high absorption capacity of white-core rice and white-belly rice, rice grains of sevral varieties were fractionated into white-core grains, white-belly grains, and non white-core and non white-belly grains. Then contents of amylose and protein, and absorption capacity were measured in each fractions. As the result, no difference in the content of amylose and protein could be detected between white-core and non-white core grains, but a clear difference in absorption rate was observed. Similarly, no difference in the content of amylose and protein could be detected between white-belly and non white-belly grains, but a clear difference in absorption rate was observed. On the other hand, the absorption capacity of non white-core and non white-belly grains fractionated from white-core rice did not clearly differ from that fractionated from non white-core rice. Consequently, it was estimated that the high water-absorption capacity of white-core rice or white-belly rice was not caused by chemical component such as contents of amylose or protein, but caused by white-core or white-belly itself, i. e., difference in the structure of rice grains.
