SAKE BREWING

INTRODUCTION

Sake is made with 4 ingredients: Rice | Water | Yeast | Koji-kin [the spores of the fungus ‘Aspergillus Oryzae’].  As there are only 4 ingredients each plays an integral part in the finished sake.  The process of brewing sake is very complex, but this is a guide for the general stages of brewing, along with some of most important Japanese sake classifications.

RICE    

After harvesting and drying the sheaves of rice, the outer husk is removed and at this stage the grain is brown rice. 

RICE POLISHING

Sake is made with white rice (with some exceptions) so the brown rice is polished/milled to remove the outer grain which reveals the white rice.  The percentage that the rice is milled along with the type of rice used is one of the factors of the style, aroma and flavour of the finished sake.  A sake made with rice which has only been lightly milled, say to 80% (20% of the outer grain milled away) will tend to have a more robust aroma and flavour than a sake made with highly polished rice.  This is largely because a rice grain contains most of the fats, oils, minerals and proteins in the outside of the grain and so the more of the outside of the grain is left the more of these elements are in the finished sake.  The Toji [Master Brewer] may decide to use highly polished rice to remove unwanted fats, oils, minerals and proteins from the rice to produce a sake that is more delicate and refined in aroma and flavour. 

RICE GRADING

When the rice has been highly polished to 60% or less of the rice grain remaining (40% or more removed) the sake made with this rice can then legally be designated under the Japanese classification of GINJO sake (it must also meet the quality requirements that the sake has a good flavour, colour and luster).   If the rice has been polished even further to 50% or less of the rice remaining (50% or more removed) then the sake can be designated under the classification of DAIGINJO (it must also meet the quality requirements that the sake has a good flavour, colour and luster).  Many regard these as the ‘premium’ grades of sake or ‘best’ sake, we prefer to call them a style or type of sake.  Ginjo and Daiginjo are relatively new styles and so sake that aren’t in these categories are more traditional and tend to give different flavour and aroma profiles and also match with different types of food.

SAKE RICE VS TABLE RICE

Traditionally, sake was made using the same rice people would eat [table rice], however over time particular strains of rice have been bred just to make sake and these varieties are known as Sakamai [sake rice]. Sakamai tends to be a large grained rice with a large opaque white centre in which the starch is concentrated, which means that the outside that contains the fats, proteins, minerals & amino acids are easily polished off to produce a ‘clean’ style of sake.  The starch in table rice tends to be more evenly spread out in the grain and so the fats, proteins, minerals and amino acids are in a higher ratio (which is exactly why they are tasty to eat). So generally speaking a sake made with table rice will have a more robust and traditional flavour and sake made with sake rice will have a cleaner more refined flavour.  The type and milling rate of the rice goes hand in hand here to distinguish the end flavours in the sake.

RICE VARIETIES

In Japan rice is planted between April to June, then harvested between August to October depending on the variety, and the brewing season commences after this, in Japan’s colder months, and runs between the end of October and the beginning of April (some big commercial breweries do brew year round).  There are hundreds of rice varieties, but there are about a dozen most commonly used for sake brewing with the top three being: 1.Yamadanishiki 2.Gohyakumangoku 3.Miyamanishiki which make up about 70% of the total hectares of rice paddies planted for sake production in Japan*.  Different rice strains do produce different flavour profiles in the resulting sake, however it is generally much harder to pick the rice type while drinking a sake, than for example the picking the grape variety while drinking wine, as there as so many other factors involved in the finished sake such as the brewing techniques used.  The Toji is often choosing the rice type as it is better for making a particular style of sake, for example Yamadanishiki is the most commonly used rice type for making Daiginjo sake.

THE BREWING PROCESS

After the rice is polished, it is washed, soaked & cooked by steaming it.

MAKING KOJI

This steamed rice is then taken to the koji room, which is a small room kept at very hot and humid conditions (much like a sauna).  The steamed rice is laid on a cedar table and sprinkled with koji spores, which is the mould that breaks down the starch in the rice grain into sugar (it is sugar that converts into alcohol during ferment later in the brewing process.) The koji-kin is massaged into the rice and then the rice is placed in containers and left in the koji room for about 2 days to allow the koji-kin time to start the conversion process of starch into sugar.  

SAKE YEAST

Yeast is the organism that creates fermentation by converting sugar into alcohol, and for sake brewing alone there are dozens of strains of yeast being used, with new varieties being discovered and ancient varieties being rediscovered. The yeast that the Toji [master brewer] selects for their sake will influence everything from the fragrance of the sake to its flavour and acidity. Most Toji use cultivated yeasts today, but many of our artisanal Kura still use wild yeasts naturally growing in their breweries.  The small ferment tank where the yeast starter begins is known as the moto or shubo and is designed to let the yeast multiply and start fermenting before adding it with more steamed rice, koji and water in a larger tank to make the main ferment or moromi.  

SAKE FERMENTATION

It is at the moto stage of the brewing process that the Toji creates 1 of 3 main styles or classifications of sake.  If they use the traditional method of grinding the moto together with wooden paddles the sake created will be known as a KIMOTO sake.  If they skip this mashing step and continue to make the main ferment the sake will be known as a YAMAHAI sake.  If the Toji adds some lactic acid to the moto before creating the main mash the sake style will be known as SOKUJO, which is the most common method used in brewing today as it is easier and faster.  If the sake doesn’t list that it is Yamahai or Kimoto you can assume it is most likely made with the Sokujo method.  Sake made in both the Yamahai or Kimoto method tend to be a more robust sake often with earthier or more traditional flavours than a Sokujo sake which tends to be a cleaner flavour.  To make the main mash or moromi the Toji usually uses what is known as the San Dan Jikomi method where they will continue to add 3 more additions of steamed rice, koji and water (over four days) in the main ferment tank until it reaches the desired quantity and then it is left to ferment for about 2 weeks for the Sokujo method or about one month for Kimoto and Yamahai.

MULTIPLE PARALLEL FERMENTATION

During this time the ingredients go through what is known as Multiple Parallel Fermentation where the conversion of the starch in the rice grain into sugar (by the koji mould) and the conversion of sugar into alcohol (by the yeast) are happening at the same time.  The result is that undiluted sake has an alcohol content of approximately 18-20%, which is higher than any other naturally fermented beverage. 

What sets sake fermentation apart from wine and beer fermentation?

Wine fermentation is known as Simple Fermentation as grapes already contain a high percentage of sugar naturally, so fermentation can occur spontaneously due to the yeast on the grape skins or with the addition of cultured yeast.

Beer fermentation is known as Separate Fermentation as the brewer malts the grain to first develop the enzymes required to change the grains starches into sugars.  Then the sugar is converted into alcohol by yeast.  In beer these are two separate stages, unlike sake where they happen simultaneously (or parallel).  

WATER

During many of the stages of sake brewing huge amounts of water are used from washing, soaking and steaming the rice to adding water for the ferment, to sometimes adding water to dilute the alcohol level in the finished sake and so a pure water source is vital.  For this reason most Kura[Sake Brewery] are established near a pure and abundant water supply.  The various minerals in water is one of the key elements as to whether it is considered desirable for sake brewing as some minerals aid in the fermentation process while particular minerals can be detrimental.  

Water can generally be described as ‘soft water’ or ‘hard water’ due to the level of minerals in it. Water that has a lower mineral content is considered soft water and generally creates a slower ferment where the yeast doesn’t have to work as hard and the resultant sake tends to be softer and sweeter on the palate.  Water that has a higher mineral content is considered hard water and generally creates a faster ferment, and so the yeast needs to be stronger and so the resultant sake tends to be more robust and often drier on the palate.

CLASSIFICATION OF SAKE

After the ferment has finished the sake will be one of the following 3 classifications of sake dependent on what the Toji had decided to create:

*JUNMAI or ‘Pure Rice’ sake has no additions added and is only made with the 4 natural ingredients.  Junmai sake tends to be a more full bodied and complex style of sake.  Only about 10% of all sake produced is Junmai.  At Black Market Sake we only import and sell JUNMAI sake.

*HONJOZO sake is where a certain percentage of distilled alcohol is added to the brew before pressing.  Up to a quarter of the alcohol in a Honjozo can be derived from pure ethanol (or up to 10% of the total weight of the white rice used).  To be classified Honjozo  the rice must have also been polished to 70% or less or the rice grain remaining.

*FUTSU sake is by far the most prevalent sake on the market and makes up about 75% of the sake market.  This ‘regular’ or ‘table sake’ has no rice milling requirements and has often very high levels of distilled alcohol added before pressing.  Futsu sake also often contains added sugars, starches and other additives.

POST-FERMENTATION

After fermentation is finished the liquid is separated from the solids.  The most common method nowadays is with a large automated press called an ‘assakuki’.  Many artisan sake breweries do still use the traditional methods though, where the moromi [main ferment] is placed in canvas/cloth bags and they are either hung to allow the liquid to naturally drip out of the bags [this is known as SHIZUKU or droplet sake] , or they can be placed in a traditional press called a ‘fune’ where the natural weight of the bags on top of each other gently presses out the liquid [this is known as ARABASHIRI or free run sake] or it will be gently pressed with either a metal press or by adding weight onto a wooden beam press.

CLARIFICATION & STABILISATION - "to do or not to do"

After pressing, many sake are then filtered again, but this time with active charcoal powder which strips out flavour, colour or particles in the sake that a brewery may consider undesirable .  

PASTEURISATION

Many sake will then be heat treated to pasteurise it. A brewery will do this to stabilise the sake by halting any further enzyme action.  Then the sake will be stored generally for a 3-6 months before any blending of tanks occurs.  Many sake will then be diluted with spring water to bring down the alcohol content, particularly in the case of Honjozo or Futsu sake where pure alcohol has been added to the brew.  Then a final pasteurisation is done at the time of bottling.  At this stage the sake will be sold for drinking.

Many artisan brewers prefer not to ‘clarify or stabilize’ their sake with these techniques however. When these brewing techniques have NOT been used look for these terms: 

                MUROKA = no charcoal filtration                

                NAMA = no pasteurisation        

                GENSHU = no dilution with spring water

STYLISTIC EXPRESSIONS

NIGORI - Cloudy Sake

Nigori is a style where fine sediment or lees (Sake Kasu)  has been deliberately left in the sake. This can be achieved via direct bottling or alternatively adding the lees or Kasu back into the brew.

KOSHU - Aged Sake

The colour of Sake deepens and the aroma gains in depth over time, producing a complex and powerful drink. the variety of colour of Koshu Sake varies greatly. Caring factors are predominately related to the different acidities in Sake, namely Amino acids.