Sake brewing

The brewing of sake retains much ritual and tradition. The Master Brewers (the toji) go about their tasks in the kura, brewing in the coldest months of the year. The toji are an elite breed of artisan that can trace their origins back to the Edo period. They develop their knowledge and stature over many years of practical experience, starting with the most menial of tasks and enduring long hours of heavy manual labour.

The brewers lived in kura for all the 100 days of the brewing season in past times and were forbidden to leave the establishment until after the final mash had begun. Nowadays machines are employed for the heaviest work and the toji work alongside university-trained technicians.

The key ingredients of sake are water and rice. Some 25 kL of water are used for each ton of rice.

The water should be colourless, tasteless and odourless and should contain only traces of minerals and organic components. Again as for beer and gin, sake making sprang from locations where the water was highly prized. For sake this was the Miyamizu water from Nishinomiya, a port in Nada. The water here actually emerges from three sources: subterranean water from the local river, an adjacent mountain, and seawater. The waters mix below a thick layer of fossilised shells and are filtered through it as the stream rises to the surface. The mountain water is rich in carbonates, phosphate and potassium. It also contains much iron, but this is not a problem because it is oxidised by acids in the river water. These days Miyamizu tends to be produced synthetically and is further refined by filtration and aeration.

The rice employed for sake production is the short grain japonica variety that becomes sticky when cooked (Fig. 8.7). It is polished more than is customarily the case for food use. Fifteen per cent of the material (the outer layers) is removed to take down the levels of protein, lipid and minerals that would jeopardise clarity.

Rice is either grown by the brewer or is purchased under subcontract. Two-thirds of the rice is yamadanishika, which originated in the Hyogo prefecture. Breeding has led to greatly improved yields and agronomic characteristics in the rice varieties that are available.

The basic techniques employed in sake brewing have not changed since the late sixteenth century. The process comprises multiple parallel fermentations.

Saccharification of starch and fermentation of sugar to alcohol occur simultaneously. For the former, koji mould (A. oryzae) produces starch-degrading enzymes that generate the fermentable sugar. This is converted by the sake yeast (Saccharomyces cerevisiae var. sake) to alcohol. The fact that both processes are occurring side by side rather than sequentially means that the yeast does not encounter such a high initial sugar concentration so as to be inhibited. Accordingly the alcohol content achieved can be very high - perhaps 20% ABV - which is higher than for any other directly fermented beverage. The sake yeast actually tolerates up to 30% ethanol.

In overview, steamed rice and water treated with koji mould are added in three separate stages to a highly concentrated yeast mash (moto). The temperature of the final mash (moromi) is maintained at around 15°C and fermentation is allowed to proceed up to 18 days. Accordingly, the basic sequence is making sake is (1) making koji rice; (2) preparing moto and (3) brewing (tsukuri).

Polishing, steeping and steaming

White rice with a slightly larger grain size than that generally used for food is reduced in weight by 25-30% (or more than 50% for some premium sakes) by the removal of outer layers. The latter jeopardise clarity and flavour and also impact the manner by which the mould grows. The more the polishing undertaken, the cleaner the sake.

The grain is then steeped in water until it reaches around 30% moisture and is then transferred to a large wooden tub (koshiki) with holes in the bottom that admit steam. The mix is placed over a metal tub containing boiling water. This sterilises and gelatinises the rice, rendering it susceptible to the action of koji.

After 50-60 min the rice is removed, divided and cooled depending on which stage in the brewing process it is going to be used in.

Making koji

Koji comprises A. oryzae, which furnishes the necessary hydrolytic enzymes (a-glucosidase, glucoamylase, transglucosidase, acid protease, carboxypepti-dase) for digesting the starch and the protein. The nature of the process is such that organisms other than the sake yeast will also develop. These include film-forming yeast, micrococci, bacilli and lactic acid bacteria. The rice employed for koji is more refined than the bulk of steamed rice. After steaming, one-fifth of the rice is removed from the koshiki and cooled to about 30°C. It is transferred to a double-walled solar-like room that retains heat. Dried spores of A. oryzae are scattered over the surface and kneaded in. Several hours later, the mix is transferred to shallow Japanese cedar wood trays (45 cm x 30 cm x 5.1 cm) that are put on shelves and covered with a cloth. As the koji mould grows, the temperature rises, so the mix is stirred twice every 4h. After 40-45 h, the boxes are removed and advantage is taken of the low temperatures outside to stop the growth of koji. After cooling, the koji mix is light, dry and flaky and has a distinct aroma of horse chestnuts.

Making moto

The koji rice for making moto starter is basically treated in the same manner; however, the process is prolonged in order that even higher levels of enzymes are produced. Moto is the seed mash and represents less than 10% of the total rice.

The longest standing method of moto production is mizu moto (bodai moto). Three kilograms of steamed rice already adventitiously infected with yeast from the air is sealed in a cloth bag and buried within uncooked polished rice (87 kg) to which is added 130 L of water. After 4-5 days, the water becomes distinctly cloudy and bubbly and is sour. It is removed by filtration and the polished rice is steamed. A second mash is then produced with this yeasty water, all of the steamed rice and a further 40 kg of koji rice. The moto is ready for use after 5 days.

The disadvantage of this procedure is the emergence of high levels of lactic acid bacteria, causing the ensuing sake to be sour.

Since the 1920s the kimoto method has become the main approach to making moto. The mix comprises 75 kg steamed rice, 30 kg koji rice and 108 L of water. This is divided in the early evening into 16 shallow wooden tubs, each of 70 cm diameter. Toji stir the mixture every 3-4 h through the night (cooling by ambient chill air) and grind the moto the next day using long bamboo poles to which wooden panels are attached. The rice is rubbed against the bottom of the wooden tubs until the grains are reduced to approximately a third of their size and the mash comprises a thick paste. This procedure accelerates the activity of the koji.

The paste is transferred to a single large wooden vat and left for 2-3 days at 8°C. Then buckets of hot water are dropped into the mash, thereby raising the temperature and stimulating airborne yeasts into fermentation. The mix is maintained at 25°C and 20-25 days later, it is used as a starter for the main mash.

It is understood that in the early stages of the process, lactic acid bacteria prevent the growth of other, less desirable organisms. Later on the alcohol developed by yeast kills the lactic acid bacteria and any unwanted wild yeast.

Two other methods have evolved for making moto. The Yamahi process has the same principles as above, but there is an initial mixing of pure koji rice with water so as to accelerate saccharification before the addition of steamed rice. This has become the most popular method. The Sokujo process again has the same basic principle as for raw moto, but here the koji rice is mixed with water and lactic acid added to 5%. At the same time, a pure culture of sake yeast is added to seed the fermentation. Steamed rice is mixed in before cooling and leaving for 2-3 days. Dakitaru is used to raise the temperature to 20°C. After 10-15 days, the mash is ready to use as a starter for the main mash.


After the koji and moto are prepared, they are mixed over 4 days. This is traditionally in large wooden vats (7-20 kL). Increasingly large amounts of rice, koji rice and water are added to the moto on the first, third and fourth days. The addition rates (relative to moto) are 1 : 1 on the first day, 2: 1 on the third day and 4: 1 on the fourth day. Through the first and second days, the temperature is allowed to rise to 15°C and the whole is left uncovered. The endogenous acidity prevents the growth of spoilage bacteria. On the third day, the temperature is lowered to 9-10° C and this further suppresses infection. After the fourth-day addition, the ensuing 15-18 days represent a challenge for temperature control, unless the facilities are sufficiently modern to incorporate cooling.

Traditional brewers still operate in the winter months, with the use of slatted windows for cooling. In modern facilities, brewing can proceed around the year.

After 15-18 days, the mixture is filtered through weighted long narrow cotton sacks over a wooden 'sake boat' (sakafune). The sake trickles through a spigot at the base of the boat. The residual lees are sold for the pickling of vegetables and for use in cooking.

New sake is held for 10 days at a low temperature, during which time glucose and acid levels are enzymically lowered. Then it is pasteurised at 60°C and transferred to sealed vats, traditionally fabricated from Japanese cedar, where it will be held for 6-12 months. This allows a mellowing of the product which starts as being yellow, harsh and smelling of koji. During ageing, characters are developed in the sake from the wood. After ageing there will be a blending ('marrying') followed by dilution with water to a final strength of 15-17% ABV and bottling.


Mill, steep, steam

Mill, steep, steam

Filter, pasteurise, store, blend, package, pasteurise

Filter, pasteurise, store, blend, package, pasteurise


Fig. 8.8 Overview of sake production.

Modern sake making

In modern facilities, the vessels are likely to be fabricated from stainless steel. Rectified alcohol is likely to be employed as a proportion of the sake alcohol, and glucose, lactic acid and monosodium glutamate may also play a role in 'tripling the sake' (cf. earlier). These are added to the final mash as a fourth addition. There is extensive use nowadays of the premier sake yeast strains, with cross-breeding to combine the best properties in a single strain.

In the latest moto processes at high temperature (koon toka mota), the moto mash is raised to 55°C for 5-8 h. Lactic acid is added and the mix is cooled to 20°C prior to the addition of yeast. The entire process takes 5-7 days. It may be computer-controlled. Activated charcoal may be employed in place of sake boats.

A simplified overview of sake production is offered in Fig. 8.8.

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