This paper describes the features of new characteristic rice cultivars developed in the Hokuriku region, especially Hokuriku +00 (floury mutant rice) and Hokuriku +03 (sugary mutant rice), in comparison with Koshihikari. Using Hokuriku +00, it is easy to make fine rice flour because the starch granules for this cultivar are globular and small. Therefore, this cultivar is popular because it is easy to handle. Hokuriku +03 has a high proportion of bran and high g-aminobutyric acid (GABA) content. The fineness of Hokuriku +00 rice flour and the component parts of Hokuriku +03 are promising as raw material for processing.
Heat moisture treatment (HMT) is a processing method used to improve the physicochemical properties of starch. Here, to inform technology with respect to increasing resistant starch (RS) in rice, three rice flours with different starch structures-namely, Koshihikari, Koshinokaori, and Goami2 (GA2)-were treated at 120 ℃ and 14 %-26 % humidity and compared with cornstarch. HMT increased the RS content of all specimens, with GA2 showing a marked RS increase up to 11.0 %. HMT also increased the gelatinization temperature (T gel ) of all samples, as shown by differential scanning calorimetry, and RS content tended to increase with increasing T gel values. As shown by the increase in relative crystallinity by X-ray diffraction and change in the iodine absorption spectrum, HMT easily changed the starch structure in GA2, leading to increased RS. These results support GA2 as a suitable rice cultivar for bio-functional rice products such as low glycemic index foods.
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