Brown rice is highly milled for use in making sake, in contrast to use as a staple food. The ratio (percentage by weight) of milled rice to original brown rice is used as a technical index in sake brewing, which is called the milling ratio . Milling ratios usually range from 75 to 35%. The average milling ratio was 66% in the 2005 sake brewing season. The main purpose of milling is to remove proteins, lipids and inorganic substances such as potassium and phosphate, which are abundant in the germ and surface fraction of rice grains. An excess of these constituents negatively affects sake quality. 1) Although the quality of sake increases when low milling ratios are used, the cost of sake production also increases because the cost of rice is significant in the entire process. Consequently, there is great interest in producing high quality of sake using rice grains having a high milling ratio.As the milling ratio decreases, the starch content gradually increases while the content of protein, crude fat and inorganic substances (ash) decreases.1,2) With respect to protein composition, the amount of protein body I (PBI) and protein body II (PBII) decreases with decreasing milling ratio, while the ratio of PBI PBII does not change. 3)Concerning the composition of crude fat, the ratio of saturated to unsaturated fatty acids increases.4) Pasting temperature as measured by amylography was reported to decrease with decreasing milling ratio.5) While differences in granule size, and physicochemical and structural properties in starch found in the outer layer (92 75%) versus the central core (below 75%) of 92% milled rice grains have been reported, 6,7) similar information for rice grains having a milling ratio of less than 75% (appropriate for use in sake brewing) is not currently available.It has been proposed that the amylose amylopectin ratio among rice cultivars affects the sake brewing process because a low amylose content has been reported to result in high enzyme digestibility of steamed rice grains. 8,9) Amylopectin chain length distribution and retrogradation properties have also been observed to affect enzyme digestibility of steamed rice grains. In the present study, the physicochemical and structural properties of endosperm starches and rice flours prepared from milled Japanese rice grains of various milling ratios were examined in order to clarify the relationship between milling ratio and starch properties of milled rice grains. MATERIALS AND METHODS Materials.Three Japanese short grain varieties were harvested during the 2004 season in Japan. Yamadanishiki (grown at Hyogo) and Gohyakumangoku (grown at Niigata) are sake type rices, and Nipponbare (grown at Saitama) is a cooking type rice.Brown rice was milled from 90 to 70% of its original weight using a milling machine (TM 05; Satake Co., Ltd., Higashi Hiroshima, Japan) at a rate of 1000 rpm. It was then milled from 60 to 30% of its original weight using a different milling machine (HS01, CHIYODA Co. Ltd., Hiroshima, Japan) at a rate of 1700 rpm. Rice flour wa...