The structure of the hot-water soluble components in the starch granules of new Japanese rice cultivars |
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Authors: | H Mizukami Y Takeda S Hizukuri |
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Institution: | a United Graduate School of Agricultural Sciences, Kagoshima University, 1-21-24, Korimoto, Kagoshima 890-0065, Japan b Kumamoto Food Processing Research Institute, 3-11-38, Higashi-machi, Kumamoto 862-0901, Japan c Department of Biochemical Science and Technology, Faculty of Agriculture,Kagoshima University, 1-21-24, Korimoto, Kagoshima 890-0065, Japan |
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Abstract: | In this study, the structures of the hot-water (80°C) soluble starch fractions (HWS) of six new Japanese rice cultivars (Saikai 194, Saikai 198, Hokuriku 149, Suigen 258, Hoshiyutaka, and Saikai 184) were investigated following a previous study Mizukami, H., Hizukuri, S. and Takeda, Y. Structures and pasting properties of starches from new characteristic rice cultivars, Oyo Toshitu Kagaku (J. Appl. Glycosci.) 43 (1996) 15–23]. The HWS were subfractionated into 1-butanol-precipitate (SAM) and supernatant (SAP) fractions. The yields of the SAM and SAP fractions were 0.3%–2.4% and 3.1%–4.1% by starch weight, respectively. The Hoshiyutaka and the Saikai 184 yielded both relatively large (2.4%) and small amounts (0.3%) of SAM. The SAM were small amylose molecules with a
n between 320 and 420 and a
w between 950 and 1850. The SAM from the Hoshiyutaka and the Saikai 184 were the larger molecules with
n 390 and 420, respectively, and having slightly more branches (6.0 and 8.1) than those from the others (1.5–4.5). The SAP were smaller molecules having a
n between 60 and 190 as compared to the SAM. The SAP was composed of small amylopectin molecules (
n 280–790, CL 17–32, β-amylolysis limit (β-AL), 54%–68%) including very small amylose molecules (
n 24–34) having an average number of branch linkage (
) of between 0.4 and 0.5. Both the amount and the structures of hot-water-extractable rice starch fractions vary with cultivar, and may influence their cooking properties. |
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Keywords: | Rice cultivars Hot-water-extractable fractions Japanese rice Starch |
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