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Anna Greenhous: on the unique process of making sake

Published:  03 July, 2013

Brewing sake is a complicated business, premium sake-brewing being an incredibly labour-intensive and so, expensive process. This month Anna Greenhous looks at how sake is made and what makes this process unique.


Brewing sake is a complicated business, premium sake-brewing being an incredibly labour-intensive and so, expensive process. This month I look at how sake is made and what makes this process unique.


The problem with describing the sake-brewing process is that there are so many parts of the process that can be done slightly differently, all changing the style of the final sake! The focus here is on the general process of making premium sake, but bear in mind there are many exceptions which I'll go into in later columns.


The main ingredients for sake are rice, water, yeast, and koji (mould).


Sake is made from the short-grained "Japonica" rice. Although sake can be made from everyday consumable rice, better quality sake tends to be made from varieties specifically grown for sake brewing called "sakamai".


There are lots of different varieties of sakamai, each giving different flavours to sake in a similar way grape varieties do to wine, although not to the same degree. Different varieties are suited to growing in different regions, rice varieties often being associated with specific places, although there are no rules restricting their cultivation to these areas and rice can be transported across Japan to be made into sake anywhere.


Yamada Nishiki, (associated with Hyogo prefecture/state) is generally considered the best rice for sake, making elegant, fruity sake with the potential to age well. Gohyaku Mangoku (Niigata) is the most commonly used due to its suitability for machine-production making light, clean flavoured sake. Miyama Nishiki (Nagano), a hardy rice variety which grows well in areas in the north which are too cold for others, tends to have rice notes, whilst Omachi (Okayama) produces earthier styles.


One of the most significant factors in determining a sake style is the degree to which the rice grain has been milled down. Under the husk, in the outer parts of the rice grain, are fats, amino acids and proteins that can create off-flavours. Towards the centre the starch is more concentrated.


Sakamai is more suitable for sake brewing for a number of reasons, most importantly because it has a more defined starch pocket (shinpaku) in the centre of the grain, making it easier to remove the fats and proteins reducing chances of off-flavours.


The more the rice grain is milled down, the finer and cleaner the flavours. Premium sake is categorized by the percentage of the grain left after the rice has been milled down (seimai-buai). Ginjo (premium sake) is polished down so that a maximum of 60% of the grain remains, Daiginjo (ultra-premium) so that 50% or less remains.


Sake contains roughly 80% water. It's used throughout the sake-making process: to wash, soak, steam and dissolve the rice to prepare it for fermentation, and finally to adjust the alcohol level. It's important the water does not contain anything which could be harmful to the sake-brewing process as the rice will absorb whatever is in the water. Iron and manganese cause discolouration and bad aromas, whilst phosphoric acid, potassium and magnesium are good for sake-brewing, enhancing the growth of koji and yeast.


Hard water enables vigorous, shorter fermentation resulting in drier, crisper styles.


Sake made from soft water, by contrast, creates fuller, sweeter styles soft on the palate due to a longer, slower fermentation.


Traditionally sake breweries were built next to natural sources of good brewing water. Nada, the most famous region for making sake has water particularly suitable for sake-making ('Miyamizu').


These days, breweries are not reliant on natural sources of water as they're able to manipulate and treat water artificially to create water suitable for brewing.


Different strains of yeast also have a direct impact on the flavours of sake. Wild yeasts are not as widely used as they were in the past due to their unreliability. Yeasts are generally cultivated specifically for fermentation and often associated with specific regions and regional sake-brewing guilds, although any yeast can be used anywhere in Japan.


New yeasts are constantly developed and assigned numbers by the Central Brewer's Union. No.9, which helps create the distinctive fruity aromas and flavours often found in ginjo sake, is the most famous.

Koji, (aspergillus oryzae) is the mould used to turn the starch in the rice into fermentable sugar. Aromas and flavours from the koji, such as sweet chestnut, may be noticeable in the final sake.

A very small amount of corn or rice alcohol (approx 2%) may be added to pull out the aromas and lighten Ginjo and Daiginjo sake. Junmai is sake with no alcohol added. Cheaper sake may have alcohol added too for a different purpose. Lower end sake may have alcohol added simply to increase yields.


The Brewing Process:
First the rice is polished down. The rice is then washed, soaked and steamed. 20% of the steamed rice is taken to the hot and humid koji room and laid out onto long tables. Koji spores are then sprinkled over the rice, breaking down the starch into sugars over a couple of days.


The koji rice is then brought back to the original tank and added to the rest of the rice, along with more water and yeasts. The process of multiple-parallel-fermentation (unique to sake) begins. The koji breaks down the starch into sugars, while the yeasts simultaneously ferment the sugars into alcohol. This is a complicated process which needs to be carefully monitored and controlled with constant mixing to ensure moisture and the temperature is evenly spread throughout.


The temperature at which this is done affects the flavour and style of the sake. This fermentation takes roughly a month and can be done by machine or by hand.


Once fermented, the sake is approximately 20% alcohol. This is usually reduced with the addition of water to around 12 to 16% (unless proof-strength Genshu sake). Alcohol may or may not also be added at this point. The rice solids are then separated from the sake by pressing and filtering (unless Nigorizake in which some rice solids remain). The sake is then pasteurized (unless Namazake, unpasteurised sake) to preserve and stabilise it. This may happen before or after bottling.


Next month, I'll be explaining the difference between the many types of sake and recommending typical examples easily available to try through the off and on-trade.


For more on sake follow Anna on Twitter: @tastewinesake