Characteristics of the starch and protein composition of rice grains used for awamori
2019
Okuda, M. (National Research Institute of Brewing, Higashihiroshima (Japan)) | Joyo, M. | Fukuda, H. | Tamamura, T.
Recently, the properties of Thai non-broken rice for the production of awamori have varied significantly among shipments imported from Thailand, and these variations make the production of awamori difficult. In the present study, we investigated the starch and protein properties of Thai rice used for awamori production compared with Nipponbare, which is used as a cultivar for sake making, because these properties have the possibilities of affecting the water absorption ratio and enzyme digestibility of steamed rice grains. The results of individual alkali solubility testing and DSC (= Differential Scanning Calorimeter) analyzing showed that the shipments of Thai rice have mixtures of different properties in gelatinization temperature and alkali solubility. The Thai rice of high gelatinization temperature had a lower content of short-chain (DP6-8 = Degree of polymerization) of amylopectin structure than that of low temperature gelatinization and Nipponbare. This result indicated that the difference of the amylopectin structure was due to the starch synthase IIa activity from a previous report. The starch in Thai rice with a high gelatinization temperature retrogradated faster than that with a low gelatinization temperature. The analysis of protein composition showed no clear difference between the Thai rice with high gelatinization temperature and that with low gelatinization temperature although intense 60kDa protein bands were observed in Thai rice. From the above results, the mixture of cultivars in Thai rice may influence treatments of materials for the production of awamori.
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