Both of Clearspring’s sake [1] producers, Akita Seishu in Akita prefecture, and Oki Daikichi in Fukishima prefecture use traditional, hand-crafted techniques to create premium sake that offers a great delicacy of taste and aroma.
Premium versus regular
The majority of sake produced and sold in Japan is known as futsushu or ‘regular’ sake. This often has large amounts of distilled alcohol added, along with artificial flavourings and preservatives, and although some examples are perfectly drinkable, quality does vary considerably. Around 25% of sake produced, however, is designated as tokutei meishoshu, or special designation sake. These are generally considered to be premium sakes, and must meet certain strict criteria laid down by the Japanese government. Both Clearspring Tamaki and Shizengo sakes are officially classified as junmaishu, meaning that they are prepared with rice and water, without distilled alcohol, and also that they are made in accordance with strict quality standards.
How sake is made
Sake is made using a process that is unique in the world of alcoholic beverages, differing from wine, beer and spirit production methods, and known as multiple parallel fermentation. The process itself is extremely complex, but in the simplest terms, steamed rice is inoculated with a mould called koji [2]-kin in Japanese, latin name Aspergillus oryzae. Once the mould has begun to grow on the rice, this mixture is known as koji, and is an essential ingredient in the making of mirin [3], miso [4] and brown rice vinegar [5] as well as sake. The koji-kin mould breaks down the carbohydrates in the rice into sugars, which can then be fermented using a yeast starter called moto in Japanese, and it is the fact that the koji-kin and the yeast starter work simultaneously that gives the process its name.
The process
The outline above may suggest that making sake is straightforward, but this is far from the case. While in modern, large scale sake making factories the process is computer controlled throughout, traditional producers such as the ones Clearspring work with rely on their long experience to judge by sight, sound and taste how to get the procedure just right.
Precision rice polishing
Premium sake is made using special rice that has larger grains that regular table rice, and where the fats and fibres are concentrated around the outer part of the grain. One of the most important criteria used to determine the quality of a sake is what percentage of the rice grain remains after these outer parts are milled or ‘polished’ away. This figure is known as seimaibuai, and for a sake to be classed as a premium ginjoshu sake, this figure must be 60% or less. Clearspring’s Shizengo sake has a seimaibuai of 60%, while the corresponding figure for Tamaki sake is 50%, meaning that both drinks are classified as ginjoshu, and display the delicate aroma and subtle taste for which this standard of sake is renowned.
Washing and soaking, steaming and cooling
Once polished to the required degree, the sake rice is then washed to carefully remove the rice bran, before being soaked for precisely the correct length of time to ensure that the moisture content is suitable for the next phase, steaming. Once steamed, the rice is then cooled in preparation for being added to the main fermentation mix.
A bit of culture – making the koji
As mentioned above, the mould Aspergillus oryzae, or koji-kin in Japanese, is required to break down the carbohydrates in the rice into sugars. The mould is inoculated onto steamed rice, and left to propagate at a carefully controlled temperature for a number of days. The resulting mixture, known simply as koji, is then mixed with the steamed rice, water and a yeast starter called the moto, and left to ferment.
Yamahai: a special sake indeed
The moto, or yeast starter used to kick start the fermentation of the sake mixture, is made by the sake maker using yeast, koji, rice and water, and generally has a little lactic acid added to speed up its development. However, in case of Yamahai sake, the yamahai moto is made without the addition of lactic acid, and is allowed to develop naturally. This is a painstaking and time-consuming process, but it results in a sake that displays an uncommon degree of character and roundness of flavour. Clearspring’s Tamaki is one such sake, making it a relatively rare and special sake drinking experience.
Moromi: the fermentation mix
All the ingredients: steamed rice, water, koji and yeast starter, make up what is known as the moromi mash, and are added to the fermentation tank, and left for anything up to forty days. By the end of the process, the mixture has an alcohol content of 20%, giving sake the highest naturally occurring alcohol content of any beverage in the world. Water is generally added to bring this down to around 16-17%.
Pressing and filtering
Once the fermentation is complete, the mixture is carefully pressed and then filtered to remove the sake lees or kasu, and leave behind a beautifully clear beverage. The sake is also briefly heated to 65C to kill bacteria, a process that, incidentally, was carried out long before Louis Pasteur gave his name to a similar procedure in the West.
Maturation
All that remains is for pure spring water to be added to the sake to bring the ABV down to around 16%, and it is then left to mature, generally for around six months, to allow the flavour to develop.