An investigation was made for factors affecting the peculiar gelatinization characteristics observed in rice, particularly in nonglutinous line collected locally in Thailand and the Philippines in the previous report, i. e. a phenomenon with high degree of retrogradation and low breakdown irrespective of the level of amylose content.
The physical and chemical properties of rice samples were considered by the measurements of following 6 items, i. e. α-amylase activity, gelatinization heat by DSC, changes in transmittancy by photopastegraphy, RVA characteristics in starch and CWD-flour (removal-cell wall decomposition product), distribution of side chain length of amylopectin, rice during storage.
Although the high degree of retrogradation of high amylose rice was in accordance with the previous report, it is supposed that rice aging is concerned with the phenomena in which the high degree of retrogradation observed in milled rice flour (and brown rice flour) of low amylose nonglutinous rice was not observed in samples of starch and those removal-cell wall decomposition product. More studies seems to be necessary since rice aging alone cannot adequately explain this remarkable retrogradation.
