Our storage warehouse is kept to 15°C and our ice room storage warehouse is kept even colder, to -5°C. After pressing, sake is stored in separate storage tanks for each type of sake at a constant temperature to ensure stable quality and left to age slowly until autumn. This is where sake spends its final days until shipment.
New, freshly pressed sake still contains a large amount of impurities called ori (dregs) and needs to undergo dreg siphoning or filtration before pasteurization and storage. In the siphoning process, the sake is placed in tanks and left to stand for several days so that the dregs separate from the liquid and settle to the bottom, and then the dregs are removed. After the siphoning of the dregs, the sake is filtered so that is becomes transparent. Sake that has completed these two stages is pasteurized if needed and then stored a little longer.
Sake is a living thing created in alcohol fermentation by yeast. As the yeast fungus and microorganisms are alive, fermentation will continue to progress in sake that is left as is, potentially causing a loss of flavor, aroma, and clarity. In the pasteurization process, the sake is sterilized through heating and a stable aging environment is created. Pasteurization not only stabilizes the sake quality, but also enables long-term storage without the use of preservatives. This can be thought of as the wisdom of Japanese ancestors passed down since the Edo period. There are other types of sake that are not filtered or pasteurized and are stored as is in ice tanks at -5°C. Pure undiluted sake that has not been pasteurized is delicate, so it is difficult to distribute and store and only limited quantities are available as products. However, the unique luxurious aroma and fresh taste of new sake is also popular. In regular sake, the alcohol molecules and water molecules blend together while stored in tanks until bottling, and the fresh harshness of new sake calms to create a sake quality with a mellower taste and aroma.
Pasteurization is carried out twice; once immediately after pressing and once before bottling. The first time is to stabilize fermentation and the second is to enable distribution at room temperature. Bottle pasteurization in which the sake is pasteurized after it is bottled keeps the sake aroma and flavor in the bottle without releasing it, so sake that has undergone this step is very fresh. There are other types as well, such as namachozoshu (undiluted stored sake) that only undergoes pasteurization once to create a great balance between freshness and aging effects. That different types of sake can be enjoyed by altering the storage and pasteurization processes is one of its great features.
Sake that has undergone the steps of preparation from winter to the start of spring is generally stored in a storage warehouse over the summer until the following autumn to allow it to age slowly. There are different storage methods, such as in tanks or in bottles, but all methods require temperature to be controlled to the most suitable level for the sake quality; if the temperature is too high, the aging will progress too quickly. The flavor of the stored sake varies slightly by tank. The most appropriate timing for aging must be determined while tasting the sake and analyzing the components and the formula is adjusted accordingly. The mixture is diluted with water and the alcohol content is adjusted to achieve the ideal sake quality. As the sake in the tanks are genshu (undiluted sake) that has only been pressed and not otherwise altered, the alcohol content is as high as 18 to 20%. This level is the highest among fermented liquors, and the level considered to be the most palatable is around 15 to 16%. It is therefore necessary to reduce the alcohol content while adjusting the sake to maintain a good balance between aroma and flavor.
Water is used in not only this step, but in all the preparation processes, and greatly affects the flavor of the sake being brewed. Miyamizu from Nada and Fushimizu from Fushimi are famous as excellent water for sake brewing. The Miyamizu from Nada is hard water, and the Fushimizu from Fushimi is soft water. Calcium, phosphorus, and other minerals in water activate yeast, so hard water that is packed with minerals creates a short-term moromi (mash) that tends to result in a dry, flavorful sake with a slightly higher level of sourness, while using soft water creates a long-term moromi that ferments more gradually and tends to result in relatively less sour sake that is smooth, mellow, and easy to drink. We use mostly soft water at our brewery, with a characteristic sake quality that is distinctive of Wakayama and highlights both the umami and the sweetness components.
It is not true that sake gets better the longer it is stored. The best timing for the flavor of the type of sake is calculated and it is pasteurized and bottled for shipment in a way that enables as many people as possible to drink it safely with peace of mind. We hope that the sake brewed here brings happiness to each person who enjoys it.