Rice suitable for sake-brewing determines the fundamental flavor of sake
Non-glutinous Japonica rice is used to brew sake, also consumed as a staple. Many rice varieties are grown in Japan, all suitable to brew sake. Rice most suitable to brew sake is referred to as “rice suitable for sake-brewing.”
The variety of rice suitable for sake-brewing must satisfy three conditions: Large grain size, white core, and low protein content.
The most representative brands of “rice suitable for sake-brewing” are “Yamadanishiki,” “Gohyakumangoku,” “Miyamanishiki,” “Omachi,” etc. However, the production volume is nowhere close to the volume in demand to brew sake. Rice suitable for sake-brewing is difficult to grow compared to common rice. For example, “Omachi” rice is large in grain size and an excellent variety of rice large in grain size. However, long rice stalks fall over while harvesting, making it difficult to harvest by machine. Therefore, the crop acreage does not increase, with some varieties like Omachi rice decreasing in production volume year by year, which raises the cost. Thus, a significant volume of common rice is also used as sake rice.
The grain size of brown rice varies by variety. The grain weight of 1,000 grains of brown rice uniform in grain size is referred to as “1,000 grain weight.” Rice with grain weight of 25 g or greater is notably referred to as “large grain size” compared to common brown rice with grain weight between 20~22 g. While rice, large in grain size, with a white core in the center and a moist appearance is referred to as “large white core rice.” The white core consists of coarse grains of starch. If this core is large, koji mold propagates easily, which grows koji easily in the white core, an important aspect of koji preparation.
Also, water penetrates easily into the core of large white rice grains. Steaming rice hardens the outer grain and softens the inside, which makes the preparation of yeast starter and fermenting-mash easier.
Also, rice contains protein and fat. These components are required to brew sake (for example, umami flavor unique to sake is derived from amino acids created by koji mold breaking down protein). However, an excess amount of these components will compromise the flavor and aroma. Many of these components are contained in the surface layer of rice grains that get polished to brew sake.
The variety of rice suitable for sake-brewing must satisfy three conditions: Large grain size, white core, and low protein content.
The most representative brands of “rice suitable for sake-brewing” are “Yamadanishiki,” “Gohyakumangoku,” “Miyamanishiki,” “Omachi,” etc. However, the production volume is nowhere close to the volume in demand to brew sake. Rice suitable for sake-brewing is difficult to grow compared to common rice. For example, “Omachi” rice is large in grain size and an excellent variety of rice large in grain size. However, long rice stalks fall over while harvesting, making it difficult to harvest by machine. Therefore, the crop acreage does not increase, with some varieties like Omachi rice decreasing in production volume year by year, which raises the cost. Thus, a significant volume of common rice is also used as sake rice.
The grain size of brown rice varies by variety. The grain weight of 1,000 grains of brown rice uniform in grain size is referred to as “1,000 grain weight.” Rice with grain weight of 25 g or greater is notably referred to as “large grain size” compared to common brown rice with grain weight between 20~22 g. While rice, large in grain size, with a white core in the center and a moist appearance is referred to as “large white core rice.” The white core consists of coarse grains of starch. If this core is large, koji mold propagates easily, which grows koji easily in the white core, an important aspect of koji preparation.
Also, water penetrates easily into the core of large white rice grains. Steaming rice hardens the outer grain and softens the inside, which makes the preparation of yeast starter and fermenting-mash easier.
Also, rice contains protein and fat. These components are required to brew sake (for example, umami flavor unique to sake is derived from amino acids created by koji mold breaking down protein). However, an excess amount of these components will compromise the flavor and aroma. Many of these components are contained in the surface layer of rice grains that get polished to brew sake.
日本酒の味の基本を決める酒造好適米とは？
日本酒の原料として使用される米は、主食用の米（飯米）と同じジャポニカ系統の水稲うるち米に属する。わが国では多くの品種の米が栽培されており、そのうちのどの品種の米を使っても日本酒を造ることはできるが、なかでも酒造りに適した米は「酒造好適米」と呼ばれる。
酒造好適米は、一般の飯米に比べて粒が大きく（大粒米）、白い芯の部分（心白）も大きいうえに、たんぱく質含有量が少ないという３つの条件を満たした品種である。
代表的な品種は、「山田錦」、「五百万石」、「美山錦」、「雄町」などだが、その生産量はすべての酒造需要をまかなうにはとても及ばない。酒造好適米は、一般の飯米に比べて栽培がむずかしいということもある。たとえば、大粒米のなかでも「雄町」は米粒が大きく優秀な品種だが、茎が長いため結実期に倒伏し、機械での刈り取りがしにくいという欠点がある。したが って、作付け面積はなかなか増えず、雄町のように年々減少している品種もあり、価格も高い。そのため、一般の飯米もかなりの量が酒米として使われているのが現状といわれる。
玄米の粒の大きさは品種によって違う。粒の揃った玄米1000粒の重量を千粒重というが、 一般の飯米の玄米が20～22ｇであるのに対して、25ｇ以上のものを特に「大粒米」または「大粒種」と呼ぶ。そして、 大粒種のなかでも、粒の中心部（心白）が白くうるんで見えるものを「大粒心白米」という。心白はでんぶん粒が粗い部分で、これが大きいと麹カビが繁殖しやすく、麹造りの重要なポイントの１つである破精込みが容易になる。酒造好適米の検査基準では、心白の発現率は80％以上である。
その他、大粒心白米は吸水も早く、蒸すと粒の外側が硬く内側が柔らかい、いわゆる外硬内軟でさばけのよい蒸米になりやすく、酒母やもろみ中での消化性がよい、などの特徴も有する。
また、米にはたんぱく質や脂質、灰分が含まれている。これらの成分は酒造りに必要（たとえば、日本酒独特の旨みは、麹カビがたんぱく質を分解してつくるアミノ酸に由来する）だが、多すぎるとかえって、味や香りを損なってしまう。これらの成分の多くは米の表層部に含まれているため、 酒造りでは必ず米を精白するわけだが、米の内部にも少ないほうが酒の質への影響がより小さくなるわけである。