Alcoholic Fermentation
Alcoholic fermentation requires sugar and yeast. The yeast converts sugar into alcohol and carbon dioxide.
Japan Sake and Shochu Makers Association | JSS
Sake is an alcoholic beverage made from rice, koji, and water. Like wine and beer, producing sake requires fermenting the ingredients. On the contrary to what many people may believe, it is not a distilled spirit. The method of making sake may share similar processes to wine and beer making, yet making sake uses a more complicated method that is completely unique to the beverage.
Alcoholic fermentation requires sugar and yeast. The yeast converts sugar into alcohol and carbon dioxide.
When making alcohol from grain, it is necessary to break down the starch in the grain into sugar first. This process is called saccharification, and enzymes of koji-fungus take care of it in the sake production. For beer, this is done by an enzyme that activates during germination (malting). Saccharification is not necessary for wine, as grape juice already contains a lot of sugar.
What is truly unique about sake brewing is that the process of saccharification (breaking down of starch into sugar) occurs simultaneously with the alcoholic fermentation (converting sugar into alcohol) in the mash. This type of brewing technique called multiple parallel fermentation, is not found in any other alcoholic beverage. It requires highly trained skills, experience, and knowledge for a successful outcome.
Many factors affect the flavor of sake such as the hardness of water, the rice variety and milling rate, as well as the koji and yeast. Even the temperature during fermentation and the processes after pressing sake play an integral part. For more about what produces different flavors, read the sake brewing process page.
The rice is sown around April, then planted in a rice paddy around May. The brewing season from the previous winter ends by June.
The rice continues to grow. In late August, the rice flowers bloom and the rice grains become fuller.
Sake is brewed throughout winter. The manufacturing of top-quality sake often occurs during the coldest months of late January.
The rice is harvested and dried in the sun for a few weeks (or with a dryer) before milling. A new brewing season begins.
The main ingredient used to brew sake is rice. Each brewer decides on what rice or combination of rice strains they want to use for a particular sake. This may also include table rice, but generally includes rice specifically grown for sake production. As of 2020, there are approximately 900 strains of rice, out of which 126 are sake rice.
Sake rice tends to be larger in grain size compared to table rice. It is suitable for sake brewing because of its digestibility and low protein content.
An abundance of clean, high-quality water is a vital aspect of sake brewing. The process of washing and steaming the rice, brewing, and diluting all use this water. Consequently, the sake brewing processes require approximately 10 times more water than rice. Therefore, a good source of water is an indispensable factor when establishing a sake brewery. In the same way, Japanese people see the presence of a brewery as an indicator of excellent natural water in the area.
Generous rainfall and expansive mountain ranges cover Japan resulting in an abundance of underground water. The water found throughout the country contains a small amount of minerals. While some of these minerals being beneficial, others, such as iron and manganese can lead to undesired flavors and colors in the sake. Also, the hardness of the water has a huge impact on the fermentation process. Soft water makes a light flavored sake, while slightly harder water brews a structured and full-bodied sake.
Koji refers to steamed rice that is treated with koji-fungus. This fungus, or Aspergillus oryzae, is a beneficial and safe variety of mold that has enzymes that break down starch into sugar. Since it is this sugar that ferments into alcohol, while starch alone does not, it is essential to use the koji-fungal enzyme to break down rice starch into sugar first. Koji acts as the supplier of these enzymes when added to the mash.
When making koji, the brewer sprinkles spores of the koji-fungus over steamed rice. It is then mixed in and nurtured for a day to innoculate and cultivate. To learn more, read more about the koji making processes and koji types.
Yeast is the special microorganism that converts sugar into alcohol and carbon dioxide gas. Alcoholic fermentation using yeast is universal for the production of alcoholic beverages, including wine and beer. However, the types of yeast used may differ from beverage to beverage. The most commonly used yeast today is cultured yeast, however, some brewers also use wild yeast.
The knowledge and skills of sake brewers are essential for sake production. The experience of the brewer defines the quality of the sake more than the ingredients alone. Experts claim wine is 80% grape quality and 20% winemaker's skill. On the contrary, the flavor of sake is 20% rice quality and 80% brewer's skill.
The processes of sake brewing need close attention and care. Because of this, brewers must monitor it 24/7 during the brewing season. It is because of their skills that such a wide variety of flavors are possible from these simple ingredients.
