Fermentation is a preservation method used in cuisines all over the world. In Japan, fermented foods are essential elements in a meal, which is cooked according to the principle of ichiju-sansai (one soup, three main courses.) A staple dish is miso soup, made from fermented soybeans and dashi broth, which produces beneficial bacteria in the gut to assist the digestive system. It also makes meals more appetizing.
One common feature across all fermented foods in Japan is the use of koji.
What is koji?
Koji is not a yeast, a common misconception that people have. It is cooked rice or soybean inoculated with Aspergillus oryzae (A. oryzae), a fermentation culture. This naturally occurring culture is particularly prevalent in Japan, where it is called koji-kin.
In Japanese, the term kōji (麹) can be used in different ways. It can mean A. oryzae, and sometimes it also refers to all the molds in fermented foods.
Koji was first used in China in 300 BC and in Japan in AD 300. By the 10th century, demand for the mold rose and it became both a preservative and a seasoning.
Just as Japan’s flower is the cherry blossom and its bird is the green pheasant, Koji is the country’s national fungus (kokkin), crowned by the Japan Spirits & Liqueurs Makers Association in October 2006.
To the naked eye, koji is just a layer of white mold that forms on certain grains.
To make it, Aspergillus culture is added to steamed rice, soybeans or wheat, and kept in a moist and enclosed environment. After 50 hours, the mold forms and sticks to the surface of the grains.
Koji is a catalyst in the production of soy sauce, soybeans and alcohol and assists the fermentation process.
Without this mold, we wouldn’t be able to enjoy the essence of traditional sake. Koji whiskies carry umami notes and a soft and elegant texture, compared to other whisky styles.
There are three types of koji: Kome-koji (rice koji); Mugi-koji (barley koji); and Mame-koji (soybean koji).
What are the health benefits?
Like other fermented foods, koji possesses a number of powerful health benefits.
It is an excellent source of probiotics, a type of beneficial bacteria that improves gut health and nutrient absorption. Probiotics have also been linked to improving the immune and cardiovascular systems as well as reducing cholesterol levels.
Koji is rich in Vitamin B1, Vitamin B2 and Vitamin B6. These nutrients are essential to the regeneration of skin, hair and brain cells and keep them healthy. In addition, Vitamin B can balance the immune and nervous systems.
Where can you find koji?
Rice koji is the most common in Japanese products.
It is used to make rice miso, shoyu (traditional Japanese soy sauce), mirin (a kind of alcohol used in cooking), shio koji (a fermented condiment), Amazake sweet wine, Nihonshu rice wine, and vinegar.
It is also cooked into koji rice, a popular Japanese dish. Although people may be concerned that this dish is moldy, it is perfectly safe to eat and has a combination of sweet and salty flavors.
Barley koji is the ingredient for barley miso paste and shochu.
Soybean koji is key to miso, a savory condiment made from fermented beans. It can also be made by using other grains, such as barley, rice, or oats, mixed with salt and koji. It is then left to ferment for several months to years.
Miso is a rich source of vitamin K, manganese, copper and zinc. For thousands of years, it has been a staple of the Japanese diet and is considered safe for most people. A versatile ingredient, it can be used to replace salt and stock powder in some dishes.
Miso contains a large amount of salt and may not be a good option for people with an underactive thyroid (hypothyroidism). If you’re following a low-salt diet or taking a blood-thinning supplement, you should be careful when deciding to consume koji-fermented foods.
Although koji has contributed to the quintessence of Japanese cuisine, many foods inoculated with this mold are high in sodium. Excessive sodium in the diet can cause high blood pressure, even in children, which can eventually lead to heart disease, stroke, and kidney failure. To get the best benefits from koji foods, consult a doctor or nutritionist for a diet plan that best suits your health condition.
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