イネ登熱期気温と酒造用原料米のデンプン特性の年次・産地間変動

摘要

我々はこれまでに，イネ登熱期が高温になるとアミロペクチンの側鎖（枝）が長くなり，デンプンが老化しやすく蒸米が消化されにくくなることを明らかにした。また，同一品種で産地の異なる試料について解析した結果，同一品種でも産地間でデンプン特性及び蒸米の酵素消化性に差異を認めるとともに，両者の間には強い相関があり，アミロペクチンの側鎖が長い試料は蒸米の消化性が低くなっていた。このことから，各産地の登熟期の気温がこれらの特性に影響したものと考察した。さらに，清酒醸造の柏歩合の統計値と気象との関係について9年間のデータを解析した結果．清酒醸造全体の粕歩合の全国平均値と夏～秋の気温が正の相関性を示したことからも，イネ登熟期の気象は原料米及び清酒製造に大きな影響を及ぼすと推測した。%The relationship between mean air temperature after heading and starch characteristics of rice grains, which correlated with enzyme digestibility of steamed rice grains, was investigated. It was con-firmed that the difference in the temperature during grain filling was the main factor for the variation in digestibility of steamed rice grains among harvest areas even within the same rice cultivar. When the mean air temperatures during one month after heading were higher, twenty-five rice cultivars for sake making showed higher gelatinization temperatures measured by differential scanning calorimetry (DSC) . Previously, we reported that, when the gelatinization temperature was higher, the enzyme digestibility of steamed rice grains was lower. Therefore, from the previous and present studies, the enzyme digestibility of steamed rice grains can be predicted by mean air temperature after heading.