A lesson in the processing technology of Japanese sake
Sake rice (preferred rice for brewing sake) has external characteristics such as larger grain than regular short grain rice, larger Shinpaku (opaque area) at its belly, and a shallower surface groove. Internally it has lower protein and fat contents, with better water absorption to dissolve rice malt. Moreover, its hard surface and soft endosperm is ideal for sake brewing. A variety named Yamada-Nishiki, which is grown in Hyogo prefecture well, matches these characteristics and is quite popular all over Japan.
Occasionally, a variety is selected from normal non-sake rice and used in combination with sake rice.
Milling and milling degree
Different types of sake require different milling degrees of sake rice, and different milling degrees require different milling technology. Sake rice millers show their experiences and skills for optimum milling, remove fat from embryo without cracking rice, regardless of variety of rice which affect grain hardness.
Satake offers dedicated control software including various milling patterns according to rice varieties and required milling degree.
Cooling and washing rice
After milling, rice is cooled down to ambient temperature. This process is necessary to avoid cracking rice grains in the washing process that follows to remove fine bran on the surface. Generally, temperature of washing water is less than 10°C, and around 5°C is preferred for Ginjo sake. The washing process drains approximate 30-40 percent of potassium, 20 percent of phosphoric acid, little amount of sodium, magnesium, sugar, protein, amino acid and fat from rice. Washing water quality is important so that rice should not absorb calcium and iron from the water.
The purpose of soaking rice in water is to absorb water into the core of grains. It enables heat to spread around the surface of grains equally during steam heating. It is required to adjust the soaking period according to rice quality, water temperature, and milling degree. Experience and skill of the brewers are needed.
Steaming the rice after soaking will sterilise and pregelatinise the rice. The optimum steam cooking makes rice grains separate easily, hard on surface and soft inside, and less sticky on the surface, which is essential to make the saccharification process easier.
Cultivation of aspergilli
The next procedure is to inoculate pores of aspergilli into steamed rice to cultivate it.
The dedicated cultivation room is air and humidity-controlled. On the flat bed, there are wooden boxes with aerators. The temperature is controlled from the lower part.
Steamed rice is spread and flattened evenly on the bed. Temperature of the rice is controlled at around 35°C and malt is sprinkled on it.
After the process makes the rice temperature rise by 2-3°C by the malt, brewers break up rice into grains and mix in the air-conditioned room.
Air temperatures and rice layer thickness are changed in different stages. In total, it takes approximately 48-50 hours to cultivate Shubo malt and 43-45 hours for rice malt. Shubo malt is one of the ingredients of Shubo. To make it, they culture aspergilli on steamed rice (= rice malt). Then, they add steamed rice and water to make rice glycated. Finally yeast is cultivated.
Produce of Shubo
There are two kinds of Shubo: rapid brewing type and traditional type. Today, the mainstream is the former. Rapid brewing type is also subdivided into several kinds but rapid brewing Shubo is very common.
To make shubo, mother water, lactate acid, rice malt and yeast are put in a Shubo tank. At last, steamed rice is added and all ingredients are in the tank. They are mixed slowly and tenderly by a spatula. That is all for the first day.
On day two, brewers grind the surface of steamed rice slowly in several times so as not to crush rice and stir a mixture intermittently.
On days three and four, they measure the temperature of steamed rice and heat air from the lower part of the tank by stove or electric heater. It is to raise the temperature of steamed rice and the inside of the tank.
Three to four days later, Shubo becomes to contain carbon dioxide with increasing of yeast. After five or six days of the condition, a mixture becomes fizzy (Wakitsuki).
Around the days eight and nine, the temperature of Shubo may exceed setting temperature. Therefore, sometimes a quantity of Shubo is moved to a tub to let it rest. The next day, Shubo is returned to the tank again and matured more for one to two days. Produce of Shubo is completed.
Three-step brewing method - Brewers prepare ingredients in three stages. If they put shubo into a large quantity of water, malt and steam rice in one time, effects of yeast and acid are extremely weakened. It causes bacteria infestation or death of shubo; the three-step brewing method could avoid it.
Hatsuzoe, Nakazoe and Tomezoe
In Hatsuzoe of the day one, they put a quarter to one third of all ingredients in the tank. The quantity of mother water, shubo, and steamed rice are decided in advance.
Hatsuzoe is called "Second shubo" and observed with the same control as shubo. The initial temperature of each ingredient is around 12-13°C. We call ingredients "Moromi" after Hatsuzoe.
The day two is a break. It increases shubo rapidly and starts to raise the temperature of moromi gradually.
The day three is Nakazoe and they put about twice the quantity of Hatsuzoe. They control the temperature of Moromi since the temperature has risen in the tank.
Finally, the day four is Tomezoe. Nakazoe raised the temperature of Moromi (around 13°C), so it is required to watch temperature carefully again.
Process to produce Moromi
In the management of this process, we count the day of Tomezoe (4th day from the start) as the day one for Moromi.
The required number of days depends on the variety of sake. For example, 18-20 days for sake with alcohol added, 20-30 days for pure rice sake, 35-40 days for Ginjo-syu.
The numerical value is measured by each instrument to know the progress of chemical reaction. According to the value, brewers make adjustments such as acceleration of fermentation. This is a significant period, which decides the taste of sake, so there is a large chance to show the brewers" skill. With the end of producing moromi, all preparation is done.
Four step brewing method
Additives and liquid preparation differ depending on the variety of sake. At this point, sometimes "Four-step brewing method" is adopted. Additives such as glucose, succinic acid, lactic acid and syrup are not used for this method. And pure rice sake and pure rice ginjo-syu don"t include additives of alcohol and liquid preparation.
Completion of Japanese sake
1. Joso - Compression, Shibori-
To remove lees from Moromi by using bag or cloth is called "Shiboru" and compressing by the machine is called "Shiboru by Fune". In addition, the sake flowing out from the machine without compression is called "Arahashiri".
At first, Joso sake is white and cloudy because of floating fine particles. Leaving it in a tank for ten hours for precipitation is called "Oribiki".
Sake in the tank is not filtered yet, so powdery sediment and yeast are still in it. Therefore, when bottled, white and cloudy particles will be deposited at the bottom. This sake is called "Nigori sake".
2. Filtering and heating
Joso sake is still keep on being fermented in the tank and fine particles are going to float. They are removed by filtration apparatus, and decoloration, flavor adjustment and coloring prevention are done at the same time. Next, it is heated in a range from 60°C to 65°C in order to sterilise and to prevent deterioration in quality during storage (this process is called Hiire). Depends on a type of sake, hiire is conducted once or twice.
3. Storage and mixing
Sake has been stored in the tank until it is bottled. During storage, the newly made sake has a mild and a smooth taste.
When same type of sake is storage in several tanks, they are mixed to prevent individual unevenness and performed a sensory inspection and ingredient analysis.
In addition, brewers added water to control sourness and adjust alcohol content.
4. Bottling, inspection and shipment
When sake is bottled for shipment, hiire is performed in a consistent process. After bottling, floating substances are checked by a visual observation or an inspecting machine, after that they affixed the labels indicating contents having passed a quality check and ship products.