What Is Koji Mold? Everything You Need To Know

Helen Skeates
Helen Skeates
20 min read

Close-up of koji, a samurai warrior.

Adding the word “mold” to the culinary lexicon conjures up images of something disgusting and unappetizing for the majority of people. Mold worship, on the other hand, is a common trait among fermenters, cheese aficionados, and salami curators. Among our micro-epicurean allies, Aspergillus oryzae — or koji, as it has been known in Japan for generations — has one of the most historic and complex associations with humans. Throughout this and the subsequent sections, we’ll go through koji in detail for the nerds in the incubator to learn from. It’s time to find out what koji is, how it produces such a wide range of flavors, and how we may use it in the kitchen.

What Is Koji?

Miso, mirin, shoyu, and sake are all Japanese fermented foods that begin with the preparation of koji, the starter culture used to make them. Koji refers to steamed grains inoculated with koji mold, such as barley, rice, or soybeans.

Rice or other grains are soaked in water and then steamed to create koji. A temperature range of 80 to 95 degrees Fahrenheit is used for the next 36 to 48 hours before the sample is cooled, infected, and incubated.

Koji: An Ancient Mold and Its Modern Renaissance – Fermentation

Koji comes in three varieties. The first is koji rice, followed by barley koji and soybean koji (all made with koji mold and cooked grains).

Although it may seem as if koji has a foul odor and taste, this is not the case at all. Sweet, salty, and nutty flavors are all present in this dish, with a hint of floral aroma.

Some forms of koji mold can be dangerous, even though they are commonly used in foods like grains. To be on the safe side, have a look at this article on “what does mold on oatmeal look like.”

Koji mold

Yes, koji mold is a type of mold that can be found naturally in nature. Typically, it is used to make pickles, alcoholic beverages, and other fermented foods.

It’s a mold that thrives in Japan’s particular climate. In addition to digesting starch and converting it to glucose, it may also break down protein into an amino acid and liquefy fat.

Koji mold is the monarch of the Asian microorganisms because of its incredible properties. It is a mold that is fully safe and edible, unlike any other mold.

If you have koji mold, you may want to read this safety guide to find out what the most dangerous mold is.

3 Types Of Koji Mold

1. Yellow koji mold (aspergillus oryzae)

This sort of koji mold has a powerful ability to decompose material. Soy sauce, miso, and sake, among other Japanese fermented foods, all rely on this component.

2. Black koji mold (aspergillus awamori)

Its name comes from the fact that the spores are black in color. The yellow koji mold’s decomposition power is superior.

However, it has a powerful ability to break down proteins. In Okinawa, awamori is made from millet or rice distilled with black koji mold.

3. White koji mold (aspergillus kawachii)

He who discovered it is named Mr. Kawachi, and hence Aspergillus is named after him. Except for the white spores it shares with the black koji mold, it is nearly identical.

White koji mold can be used in the brewing of sake. The black koji mold is also commonly employed in the brewing of shochu (liquor).

Why should you eat koji?

Koji mold is a helpful enzyme supplement for persons with an imbalanced diet or an enzyme deficiency because it produces about 100 enzymes.

We rely on enzymes to break down, synthesize, transport, and expel nutrients from our bodies. A lack of enzymes may prevent us from metabolizing even if we have adequate minerals, vitamins, and protein, according to some experts.

Additionally, koji is a strong source of probiotics, which aids in enhancing our digestive health and nutritional absorption. It is possible that probiotics have a positive effect on our immune system, cholesterol, heart health, and even our mood.

Foods made from koji

Foods manufactured from koji are included in this list of Japanese koji-fermented foods.

  • Soybean, salt, and koji are combined to make miso. A common ingredient in Japanese cooking, miso may be found in anything from stir-fries to stews and even miso soup.
  • In order to make soy sauce, koji is dusted on soybeans and barley. Another common Japanese seasoning, it’s widely utilized in a wide variety of recipes, much like miso.
  • Mirin is a rice wine that is commonly used in Asian cuisine. Glutinous rice and koji rice are combined with shochu, a clear liquor.
  • Rice wine created from shubo (a blend of water, steamed rice, koji rice, and steamed rice) is called sake. It is also a little sweet since steamed rice is broken down into sugar by the fermentation process.
  • A sweet, fermented rice beverage made from steamed rice and koji rice, amazake is popular in Japan. Winter and summer are the best seasons for drinking amazake because it may be savored hot or cold.

Meet the Mold

The filamentous mold known as koji can be seen on bread and oranges. There are two types of molds: fungal and non-fungal (singular: hypha). Fungi have hyphae similar to plants’ roots. The network of hyphae is referred to as a mycelium, while the individual hyphae make up numerous hyphae. The mycelial mat of A. oryzae, a white to yellow-green fungus, grows on the surface of foods. For generations, it has helped the fermentation of rice, barley, and red beans since it prefers grain as a substrate. It is mostly used in Japanese cooking; its name derives from the country’s culture, and its flavor and application are essential to the cuisine. Aside from miso, sake, and soy sauce, koji is a key ingredient in a wide range of Asian dishes. This complex mold opens the door to a world of culinary possibilities in the kitchen.

Jeremy Umansky uses koji in his “vegan charcuterie” experiments. He thinks that mold can be used to make charcuterie out of vegetables in the same way as meat.

Koji has a long and illustrious history that dates all the way back to China. Neolithic pottery from the second millennium BC shows evidence of rice-based fermented wine. The first mention of utilizing mold in food preparation dates back to the Zhou period around 300 B.C., when grain-based wines and bean pastes were being prepared. Because it is a saccarifying mold, the most effective usage of koji is to break down the starches found in grains.

Koji: An Ancient Mold and Its Modern Renaissance – Fermentation

A. oryzae was isolated from other Aspergillus strains and non-related surface molds throughout time by the fusion of koji with yeasts and ash (which was introduced to modify the pH). Koji is one of the few Aspergillus molds that doesn’t create aflatoxins, which are harmful substances produced by certain molds. This resulted in a wide range of color and enzyme variants within the species A. oryzae.

Whenever a fungus injects its hyphae into a substrate, it immediately begins to grow. When koji is added to food, it alters its flavor and texture in this way. To begin, it’s important to know that koji itself has a varied flavor that can range from flowery to cheesy depending on the species variety and the grain (or other) substrate used. Furthermore, Koji creates potent enzymes that impact its “host” – whether it is a pile of rice, a whole parsnip, or a piece of pork belly. Furthermore, the enzymes in koji aren’t interrupted when the mold changes conditions on its own. When it comes to flavor and texture, koji’s enzymes are powerful no matter how old, mature, or even dead the plant is. As a result, one can dry, chill, freeze, heat, or even further ferment koji, and still taste the enchantment of the koji-filled substrates that they are composed of.

Koji produces around 50 enzymes, including amylase, protease, and lipase enzymes, which break down sugar, protein, and fat molecules, respectively. Smaller components become accessible for use in other biological processes, such as lacto-fermentation, as enzymes break down bigger molecules into their smaller component parts.

The Secret in the Sauce

As an analogy, if you think of koji as the trunk of a tree, then the branches, twigs, and leaves are the subsequent foods that koji’s main fermentation helps to produce. Douchi (black beans), miso, and soy sauce are all products of traditional secondary fermentations.

When it comes to feeding yeast, koji has always been a key player. Anything that can be done in any country in the world is to combine yeasts and sugar to make alcoholic ferments. By chewing corn to make chicha, some indigenous people of the Americas were able to accomplish this feat. In the West, brewers relied on malted grains to make their beer. Fungus is also used to make fermented drinks in Asia, the most famous of which being Japanese sake. The ritual, tradition, and lore of sake’s traditional fermentation are woven into its fabric. There are three major stages to the production process: planning, production, and post-production. To begin, koji is only found in rice that has been polished. Sweet amazake, made from the koji, is fermented into sake after the koji has finished maturing. Sake that has been exposed to the elements and germs for a longer period of time can be transformed into rice vinegar.

One of the few Asian ferments that is also a mainstay in Western kitchens is soy sauce, or shoyu in Japanese. But koji isn’t the sole ingredient in umami-rich dark liquids like soy sauce; there are numerous variations on the theme. True tamari is a by-product of miso; it’s the liquid that rises to the top during the process of fermenting. Because a batch of miso only yields a small amount of tamari, ingenious people devised methods of mass-producing tamari centuries ago. Soybeans and water were traditionally used to make tamari. Small balls of soybeans were hung outside to trap wild Aspergillus spores after they had been soaked, cooked, mashed, and shaped into balls. Soybean balls were dried and placed in enormous cedar vats with salt and water after the koji had grown on them. Today’s method is similar, except koji is now grown on steamed beans in a saltwater slurry rather than on rice or other grains. The resulting mash is then fermented for at least a year before the tamari is extracted from the bean paste and crushed under weights.

Unlike tamari, soy sauce is not a byproduct, but rather one of several varieties of fermenting a liquid-y mash made from wheat and soybeans, and soy sauce is one among them. The origins of this method can be traced back to China, although it has since spread throughout Asia. In Indonesia, for example, kecap manis is the country’s version of soy sauce. This sauce is sweeter and thicker than typical soy sauce because it contains fermented soybeans, palm sugar, star anise, galangal, and other aromatics.

As a result of mass production, soy sauce has been able to avoid the lengthy process of achieving its distinctive flavor by using industrialized shortcuts. Increasing salt and using stronger monoculture spores help manufacturers speed up the process. Some soy sauces are prepared from defatted soy grits, a byproduct of soybean oil, while others employ lower-quality components. Rapid hydrolysis or “acid hydrolysis,” in which hydrochloric acid is boiled with defatted soy meal and cornstarch to release the amino acids, is used by the cheapest brands. Buying unpasteurized, organically brewed soy sauce is the best way to appreciate the flavor-enhancing benefits of microorganisms. Not only will the taste improve, but you’ll have a more potent flavoring tool thanks to the enzymes in soy sauce.

Koji is also essential to the formation of the Asian pantry staple of bean pastes. Traditional Japanese paste, miso, is more than just a flavorful addition to your favorite Japanese soup. Fermented paste created from soybeans coupled with rice koji or barley koji has a salty, umami-rich flavor. It is the koji’s job to cut open the molecules and unleash a smorgasbord of taste.

A Culinary Revolution

Traditional methods of fermentation are being adopted and adapted around the world, and fine-tuned to suit local tastes and preferences. The procedures are still complicated, both in terms of how they are used and the results they produce. Experimentation with fermentation with koji is growing in popularity among home cooks due to its ability to enhance and magnify subtle aromas. For the time being, the koji renaissance sticks to the basics:

Koji’s first fermentation. An injected grain or other substrate is used to promote the growth and flowering of the koji mold and is then incubated. The koji-coated food can subsequently be utilized to enhance the flavor of other meals, or it can be employed as an inoculant for further fermentation.

Shio-koji. Koji is well known for its secondary fermentation products, including this one. Koji fermented grains are combined with water and salt and then re-fermented. As with traditional soy sauce, this produces an umami-rich sauce quickly and without adding its own flavor, allowing the food’s natural flavors to come through and bring forth their full potential.

Ama-koji or Amazake. This is another main secondary fermentation product of koji. Koji-fermented grain is combined with water and additional cooked grain, and is then fermented again at higher temperatures. This produces either a sweeter or sour secondary ferment, as opposed to shio-koji’s salty profile.

Koji Charcuterie

Ama-koji, or Amazake, as it’s most often known. One of the main byproducts of koji’s post-fermentation secondary fermentation is this. A mixture of koji-fermented grain, water, and additional cooked grain is then re-fermented. A sweeter or sourer secondary ferment results, as contrast to the salty flavor of shio-koji.

If the phrase “vegan charcuterie” makes you cringe, you’re not the only one who does. Umansky believes that the term “charcuterie” should be used to represent the process of giving vegetables the same texture and mouthfeel as meat through the use of classic charcuterie methods (curing, smoking, and hanging). There are different ways to preserve meats across cultures, and charcuterie is one of them, he claims. The phrase is used to characterize the approach regardless of how it is used.

Traditional cooking methods can’t fully release the taste potential of everyday items, but Koji can. With a little experimentation, you may make a smoked vegetable by cooking a vegetable al dente, then curing it with salt, herbs and spices for a few days, and then smoking it. The hyphae will reach into the vegetable and eat it, secreting their potent enzymes and bringing out flavors you recognize, if you cover it with koji before hanging it. However, the flavors of the vegetables are accentuated. To summarize, koji offers an aroma increase throughout the subsequent hang time, driving in the umami, the fifth flavor we associate with charcuterie. It is the amino acids found in these veggies that allow the proteins to be digested.

Koji isn’t just for vegan charcuterie anymore; it’s also being used with meat in innovative ways. Meats designed for fresh cooking might benefit from the dry-aged flavor of koji, which can be grown directly on the meat to soften normally tough pieces. In addition, it is used as a flavor and cure accelerator, as well as a protective mold, on salt-cured meats. Koji-cured whole muscle and salamis have shown that the active enzymes in koji allow meat to cure in about half the customary timeframe, with heightened flavor, as demonstrated in experiments. Preserved foods can benefit from koji’s capacity to lower water activity and salt content, and koji’s probiotic metabolites can be manipulated to lessen the requirement for isolated starter cultures in fermentation.

Garums are a lineage of sauces derived from traditional fish sauce that are based on meat or animal protein. During the process of making fish sauce, the enzymes in the intestines of fish really break down the meat and produce an amino-rich liquid. Instead of relying on intestinal enzymes to do their function, Koji does it all on its own. Creative animal product manipulations are already appearing in kitchens all around the world, including garums made from grasshoppers and bee pollen.

Beyond the Kitchen

Fungi breeders are attempting to improve koji’s enzyme output to increase and broaden its use in kitchens and labs as koji’s applications are explored in kitchens and labs. Polybutylene succinate (PBS), a biodegradable material found in packaging film, bags, and mulching film, is broken down by Koji. Because it produces lipase enzymes, which break down fats, koji is often utilized in washing formulas.

Even though Aspergillus oryzae and humans have co-existed for millennia, koji’s history and potential are being elevated and disseminated by new epicurean preferences and modern worldwide problem-solving. We’ve only just begun our voyage with this antique mold.

5 Common Koji Uses

Koji rice—steamed rice inoculated with koji mold and allowed to ferment for just over two days—acts as a starter for many fermented foods in traditional Japanese cuisine. Koji is also often used on barley grains and sweet potatoes, and may be found at most Asian grocery stores.

  1. Koji rice—steamed rice inoculated with koji mold and allowed to ferment for just over two days—acts as a starter for many fermented foods in traditional Japanese cuisine. Koji is also often used on barley grains and sweet potatoes, and may be found at most Asian grocery stores.
  2. Koji rice—steamed rice injected with koji mold and allowed to ferment for slightly over two days—acts as a starter for many fermented items in traditional Japanese cuisine. Koji is also often used on barley grains and sweet potatoes, and can be found in most Asian grocery stores.
  3. Traditional Japanese cuisine relies heavily on koji rice, a type of steamed rice that has been inoculated with koji mold and allowed to ferment for about two days. Koji is also often used on barley grains and sweet potatoes and can be found in most Asian grocery stores..
  4. In order to manufacture koji salt, koji rice is fermented in a solution of salt, water, and a starter culture for a period of time at room temperature. In the end, you’ll get a flavorful paste that can be used to replace salt in everything from marinades and stir-fries to soups. Try making a simple stir-fry for dinner this week.
  5. While miso paste uses koji molds to ferment a soybean and salt mash, Japanese-style soy sauce is prepared by pressing and filtering the resulting liquid, which is similar to miso paste’s final product.

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Koji Spores - Aspergillus oryzae - EDIBLE ALCHEMY %


What is koji mold culture?

Cooked rice and/or soya beans injected with the Aspergillus oryzae fermentation culture are known as koji. Koji-kin, a type of naturally occurring culture, is common in Japan, which is why so many Japanese dishes have been made over the ages employing this type of culture.

Are there different types of koji?

Three types of koji can be distinguished based on their primary ingredients: rice koji, barley koji, and soybean koji. KOJI MOLD: That’s a good question. Non-poisonous koji spores, or koji-kin, are a filamentous kind of fungus utilized in the production of koji.

What can you use koji for?

Koji is a strain of Aspergillus oryzae, a fungus that is used for a variety of culinary reasons, including the manufacturing of alcoholic beverages like sake or shch, as well as condiments like miso, mirin, and shyu, which are considered essential to Japanese cuisine (soy sauce).

What are the uses of Aspergillus oryzae?

Sake, shoyu, and miso are all classic Japanese fermented foods made from the fungus Aspergillus oryzae (soybean paste).

What is black koji?

Bacteria cannot thrive in the presence of black Koji. Citric acids are abundant in this black koji compared to other Koji-kin. The hot and humid climate in the southern part of Japan, where Shch is brewed, makes it easier for germs to flourish. That’s why Black Koji is so frequently employed.

Can you eat Koji?

When koji is combined with other foods, the umami flavor is enhanced.

Does Koji contain any allergens?

To prepare popular Japanese cuisine like miso (using fava beans or green lentils, for example) or soy sauce allergen-free, you can use koji, which is free of the 14 allergens identified by the UK Food Standards Agency (using fava beans)

Is Koji vegan?

Koji is, in fact, entirely vegan, consisting just of rice and a fungus.

Leave a query in the comments section if you still have any queries regarding Koji or its application. We’ll do our best to respond.


It’s not every day that we hear about food contaminated with mold. Mold is commonly thought of as a problem and a health threat, yet there is a specific type of mold.

After learning about koji mold and its various uses, you may want to give mold-based meals a try. It’s impossible to rule out the prospect of eating something we’ve never even contemplated eating as technology and living progress.

Helen Skeates

Helen Skeates

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