All about Koji mold

In the realm of the human food history the concept of fermentation has played a vital role. In general there is stigma attached to what we call “MOLD,” which exhibits eeriness somehow. However, throughout Asian countries the fermentation technique utilizing “mold” has advanced tremendously because of the warm and humid climate. And it is important to note that there is one mold very peculiar to the Japanese fermented food culture that is called Koji Mold, also known as “Aspergillus oryzae” in the scientific name.

What is Koji mold?

Koji Mold is only found and exists in Japan and is considered to be a valuable asset and more like cultural heritage that has been managed and nurtured by our ancestors in the past. In 2006 The Brewing Society of Japan has officially recognized Koji Mold as a national mold. Koji Mold is classified as Aspergillus genus, filamentous (stringlike) mold with a spore whose size is 5-10 μm. Its weight is so light that 1g of Koji mold contains 10 billion spores. Different from plants, Koji Mold is non-photosynthetic and asexual (no distinction between male and female).
Koji mold is basically broken down to three families: oryzae, awamori, and kawachii. At the same time alternatively it can be grouped in terms of color; oryzae as yellow Koji Mold, awamori as black Koji Mold, and kawachii as white Koji Mold (see below).

safety of Koji mold?

Speaking of the safety of Koji Mold, because of being mold, safety concern, especially on mycotoxin or aflatoxin, rises sometimes. But the latest genetic technology revealed that koji mold does not produce any toxic substances during the corse of propagation. FDA now recognizes koji mold as GRAS (Generally Recognized As Safe).

Difference between Koji Mold (aspergillus), Koji starter, and Koji

What Koji Mold is already explained in the above section. So what is Koji starter? Koji starter refers to Koji spores that are produced for the purpose of the commercial use and used by the brewers to start the fermentation process. Although Koji Mold has been the cornerstone for the Japanese fermented foods, the commercial production of Koji starter has been around only since 1860s. The commerce involving Koji starter was very secretive and monopolistic in the old days so Koji Mold-impregnated grains (rice barley, and soybeans) – we call it “KOJI”- were sold to the brewers instead. Koji contains a wide variety of enzymes also known as the storehouse of enzymes and these enzymes will help breaking down the grains; this process also known as fermentation. Also Koji is something very nutritious that is full of vitamins, minerals, and essential amino acids.

The important function of Koji Mold is to secrete hydrolysis enzyme to break down grains and beans to low molecular level so human body can easily digest. Specifically Koji Mold produces enzyme called amylase and protease. Amylase breaks down carbohydrate or starch to glucose and protease breaks down protein to amino acids.

Delicate process of Japanese Koji Making

Comparing alcohol brewing method between the West and Asia, both share the alcohol fermentation promoted by yeast but precedent sacchraization process bears big difference. Saccharaization is the process where carbohydrate or starch is being broken down to sugar by enzyme. The difference is that microorganism play a role in creation of enzyme or not; in Asia this enzyme is produced by microorganism propagated on grains but the enzyme used in the West is produced when barley is germinated. Even within Asia, say between Japan and China, there is a difference in terms of type of microorganism which plays a role for the creation of enzyme; in Japan we use mold known as Aspergillus Oryzae, and in China they use mold belonging to the genus of Rhizopus or Mucor. Speaking of Koji making, its process differs from Japan and China. In Japan Koji spores are sprinkled on grains or beans whose surface serves as culture media where Koji Mold propagates itself. In China mold is mixed with raw grains or beans to make a block type Koji.
More elaborating steps involves in the Japanese Koji making than the Chinese way of Koji making. Especially, in old days, sake brew master took his great pride to master the art of sprinkling Koji spores evenly on steamed rice.

safety of Koji mold?

Fermentation and decomposition are assimilated to each other in a sense that microorganism is involved in both process. But they are completely different from each other in the point of view of being beneficial to human beings or not. We call the process resulting in producing something good and beneficial to us "fermentation." On the other hand, the process resulting in producing something harmful or poisonous to us, such as getting food poisoning or stomachache, is called "decomposition." Most importantly, fermentation such as alcohol fermentation, lactic fermentation, or acetic fermentation is something on which we human beings have the control. Fermentation is definitely the technique of making preservable food which we have mastered in the course of the long human history.
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