Koji is steamed rice that’s had koji mold spores or koji-kin propagated onto it. The scientific name of the mold is Aspergillus Oryzae. It creates enzymes as it matures and they break down the starches in the rice into sugar that’s fermented by the yeast. Carbon dioxide and alcohol are given off. Without koji it wouldn’t be possible to make sake.
Wine is fermented from grapes. The grapes contain glucose, which is the only sugar that can be metabolized by yeast. The yeast in added to the grape juice. Beer and other beverages made from malted barley begin with starches. The brewers utilize enzymes. The barley is moistened and warmed and the enzymes break down the starches to sugars. Some of the sugars feed the yeast and others add flavor.
Sake is brewed from white rice that’s been stripped of its husk. The starch dividing enzymes come from the koji. It’s sprinkled onto steamed rice and provides the needed enzymes for saccharification. There are many different enzymes involved. Some ferment glucose. Others create sugars that don’t ferment, but affect the texture and the flavor of sake. In the making of alcoholic beverages from grains, it’s necessary to convert grain starch into sugar, and then convert the sugar into alcohol by means of yeast. Sake brewing combines these two steps by a simultaneous conversion that results in sake having a higher alcohol content than any other fermented beverage.
Sake is considered the national drink of Japan. The history of making sake dates to the 3rd century AD when literature recorded the manner and custom of taking sake. About the 3rd century BC in the late period of the Jomon Era a method of rice planting was introduced to Japan. It’s believed sake making started about the same time. Sake’s appearance resembles wine and it has a dry sherry-like taste. It’s colorless or pale yellow and contains 12 to 18 percent alcohol by volume. Sake is commonly called rice wine and is usually serve warm.
As defined by the Japanese Liquor Law, sake is made from rice, rice koji and water using fermentation and filtration processes. This refers to the traditional type of sake.During World War II sake manufacturers started adding alcohol to the process to increase the volume to make up for the shortage of sake due to the decrease in the amount of rice grown during the war. Sake is now divided into two types, with or without additives.
Koji is cultivated in a special room in the brewery or kura called the koji muro. Koji production is known as seigiku and is the center of the sake brewing. When the koji is ready it’s mixed with more steamed rice. Initially yeast and water are added. In later stages the koji is transferred into large tanks which contain sake-to-be which is in the process of fermenting.The koji-making process takes 40 to 45 hours during which the koji is checked and mixed constantly to insure the proper moisture and temperature. Heat is generated in the process and different temperatures are ideal at different stages. Variables affecting the final product are the type of rice used, pH and mineral content of the water used.
The best sake comes from using a special type of rice. This rice boasts a high starch content in its core. The rice stays intact longer during the brewing process. This enables excess oil and protein to be removed. Such rice is called Shinpaku-mai in Japanese. The taste of sake is dependent on achieving a balance between sweetness and acidity. This balance is maintained through the proper combination of steamed rice, water, yeast and koji. Skilled artisans with experience have the special insight into the subtleties of minute changes in rice, water and climate.