You must ever hear this old saying about sake brewing which goes “First Koji, Second Moto (sake mash), Third Preparation”. The process of sake brewing also starts with the most important step: Koji making. Why is it important? And how different types of Koji being used in the brewing process? Let’s have a further talk in the article below.
What makes Koji-making important?
The big difference of sake with other kinds of alcohol is the process of koji making. Yeast helps in breaking monosaccharides ( such as glucose, fructose) or disaccharides (sucrose, maltose) into alcohol, that’s why most European or American style of winemaking starts by crushing and pressing (grapes, apples), or by using maltase (hydrolysis of starch to produce maltose) which helps in the process of fermentation. But this saccharification enzyme is absent in sake rice itself, so it is needed to use Koji to provide the enzyme that breaks down starch into glucose. This enzyme later used for the growth of yeast and to produce alcohol.
Besides sake, shochu and awamori also used Koji yeast to provide enzymes that break the starch in main materials ( such as taro, wheat, rice, etc.) into glucose to produce alcohol. In this brewing process, both the method of saccharification and fermentation take place, also called as “Multiple parallel fermentation”, which is considered as a peculiar method by Western people.
Types of Koji-kin
In the process of making sake, there are three types of Koji mainly used: Yellow Koji, Black Koji, and White Koji. Let’s get to know the difference.
Yellow Koji (Ki-koji –kin)：
Yellow Koji is the most common type of Koji used in making sake, with characteristics of strong fruity aroma and low level of citric acids produced.
Because yellow koji produces smooth and elegant sake, some shochu breweries use this type of koji for the process of saccharification.
Black Koji (Kuro-koji –kin)：
It is said that Okinawa is the place of origin for black koji. Okinawa’s awamori also uses black koji for the process of saccharification. Black koji produces a high level of citric acids in this process, using low pH to inhibit bacterial growth, also creating the unique and special flavor of awamori in Okinawa.
Some shochu breweries also use this type of koji in saccharification process to gives strong and impressive flavor of shochu.
White Koji (Shiro-koji-kin)：
The origin place of white koji is Kyushu. It is said that white koji was developed by natural mutation of black koji.
The early usage of white koji in Kyushu for making shochu was to replace the disadvantage of using black koji spores that dispersed easily and stained the workers’ clothes.
Similar to black koji, white koji also produces a high level of citric acids in saccharification process, giving high acidity to sake produced. But sake produced by white koji have milder and sweeter aroma than the one that black koji produced, showing more of its original aroma and flavor.
Koji is the most important enzyme, needed in the process of brewing sake, to breaks down starch into sugar.
The most common type of Koji is Yellow Koji (Ki-koji –kin), Black Koji (Kuro-koji –kin), and White Koji (Shiro-koji-kin), with the different flavor of each sake produced.
Yellow Koji produces the fruity flavor of sake, while Black Koji and White Koji produce rich and strong flavor, with high acidity of sake. Each Koji gives variations of flavor to sake produced in their own way.