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What is the stage mashing process used to brew sake?

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Japanese sake is brewed from fermentation-mash prepared by adding yeast, steamed rice, koji, and water to the pure yeast starter cultivated in large volumes, in which alcohol ferments. Since the volume of steamed rice used to prepare the standard yeast starter is low at approximately seven to eight percent of the overall volume mashed (the yeast starter ratio is the ratio of the total volume of rice in the yeast starter to the total volume of rice used to mash the fermentation-mash one time), adding a large amount of ingredients (steamed rice, koji, and water) at once rapidly lowers the acidity of the yeast starter and the number of yeast starters. Therefore, the yeast starter cannot cultivate at the same pace, increasing the risk of bacterial contamination.    
Therefore, ingredients are not added at once, but divided and added in several stages to cultivate an adequate yeast starter while mashing. This mashing method is referred to as the “Stage-mashing process,” otherwise referred to as the “Three-stage mashing process,” as sake ingredients are divided and added in three stages. Some may suggest increasing the volume of the yeast starter to ensure safety in mashing in one stage. However, preparing the yeast starter is very time-consuming, and significantly increasing the ratio of yeast starter can compromise the aroma of sake, thus deemed unrealistic.   
The Three-stage mashing process is used to mash in three stages over a four-day period: “First stage,” “Second stage,” and the “Third stage” (also referred to as “tome-jikomi,” or the “final stage”). 
During the “first stage” on the first day, the volume after mashing grows to approximately three times the yeast starter. The mashing temperature is slightly high between 53.6~55.4 degF to revive the yeast in the yeast starter. During the “resting stage” on the second day, mashing is stopped for a day to sufficiently cultivate the yeast starter and increase the yeast in the fermentation-mash. During the “second stage” on the third day, the volume after mashing reaches approximately seven times the yeast starter at the mashing temperature between 48.2~50 degF. During the “third stage” on the fourth day, the mashing temperature drops further between 44.6~46.4 degF, and the volume grows to approximately fourteen times the yeast starter. This concludes the standard three-stage mashing process. However, the temperature is lowered to ensure safety as the mashing continues, for as the volume increases, the lactic acid concentration drops and becomes easily susceptible to bacterial contamination.  
To prepare sweet sake on the other hand, the final step requires the fermentation-mash prepared by the three-stage mashing process to be mashed one more time, referred to as the “four-stage mashing process.” 
 
 
日本酒の段仕込みとは何か
日本酒は、清酒酵母を純粋かつ大量に培養した酒母に蒸米と麹、仕込み水を加えてもろみ(醪)とし、その中で酵母にアルコール発酵をさせて造られる。しかし、通常酒母造りに使用する蒸米は仕込み量全体の7~8%程度と少ない(もろみ一仕込みの総米重量に対する酒母総米重量の割合を酒母歩合という)から、大量の原料(蒸米、麹、水)を一度に添加して仕込むと、酒母中の酸度と酵母数が急激に低くなってしまう。そのため、酵母の増殖が追いつかず、雑菌に汚染される危険性が高い。そこで、一度に原料を加えず、何度かに分けて添加し、適度な酵母の増殖を図りながら仕込んでいく方法がとられる。このような仕込み方を、「段仕込み」または「段掛け法」という。一般には3回に分けて仕込むため「三段仕込み」と呼ばれる。それなら酒母の量を増やせばよいのではという考え方もできるし、そうすれば一度に仕込んだ場合の安全度も高くなるはずである。しかし、酒母造りは非常に手間がかかる上、酒母歩合を極端に高くすると出来た酒の香味が悪くなってしまうので、現実的ではないという。
三段仕込みは、「初添え」(「添え仕込み」または「添え」ともいう)、「仲添え」(「仲仕込み」または「仲」ともいう)、「留添え」(「留仕込み」 ともいう)の三段階に分けて仕込む方法で、四日間にわたって仕込む。 
一日目の「初添え」では、仕込み後の容量は酒母の三倍程度になる。酒母中の酵母の活性を呼び戻すため、仕込み温度は12~13度とやや高い。二日目は「踊り」と称して、一日、仕込みを休む。酵母を十分に増殖させて、もろみ中の酵母の優位性を高めるためである。三日目の「仲添え」 では、仕込み後の容量は酒母の約7倍になり、仕込み温度は9~10度とする。四日目の「留添え」では、仕込み温度を7~8度とさらに低くし、容量は酒母の約14倍となる。以上が標準的な三段仕込みだが、このように仕込みが進むにしたがって温度を下げていくのは、容量の増加によって物料中の乳酸濃度が低下して雑菌に汚染されやすくなるため、温度を下げて安全性を高めているのである。 
一方、甘ロの酒を造る場合に、三段に仕込んだもろみの末期にもう一度仕込む方法があり、これを「四段仕込み」という。仕込む原料は、蒸米、 酒母、甘酒、酒粕、糖化酵素剤などがあるが、近年は酵素の利用(「酵素四段」という)が一般的になっている。
 
#alcohol #alljapannews #japanese #japanesefood #japanesesake #sake

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