Fermentation in Japan – Tradition between craftsmanship and high tech

Hardly any other food culture in the world is as deeply, naturally, and diversely influenced by fermentation as Japanese cuisine. From breakfast to dinner, from rustic village cooking to haute cuisine, fermented foods are not a trend but a fundamental part of Japanese culture. They shape taste, shelf life, nutritional value, and ultimately the Japanese understanding of time, patience, and nature.

A History of Microorganisms

The history of fermentation in Japan goes back a long way. Archaeological finds indicate that alcoholic beverages were already being produced from fermented fruits and grains in the Jōmon period (from around 14,000 BC). By the Yayoi period (from around 300 BC) at the latest, fermentation gained systematic importance with the advent of wet rice cultivation.

A decisive impetus came from China and Korea: along with Buddhism and new agricultural techniques, fermented foods also found their way to Japan. But instead of simply copying them, Japan developed its own methods, adapted to the climate, raw materials, and taste preferences. The warm, humid weather conditions proved particularly ideal for microbial life. While fermentation was primarily used for preservation in many cultures, in Japan it was increasingly used for specific flavor enhancement.

What is fermented in Japan?

In Japan, almost everything is fermented. Classic fermented staple products are soybeans, rice, barley, and wheat. These are used to make soy sauce (shoyu), miso, natto, sake, shochu, and mirin. But vegetables (tsukemono), fish (shiokara, funazushi), tea (fermented awa-bancha), and even sweets can also be fermented.

What is particularly remarkable is the matter-of-factness with which fermentation is used. It is not a special process for individual products, but a way of thinking. A cabbage is not just pickled, it is deliberately fermented. Fish is not just salted, but enzymatically transformed. Taste develops over time.

How is fermentation carried out?

Japanese fermentation is usually based on a finely tuned interaction between molds, yeasts, and bacteria. The process often begins with the deliberate inoculation of a raw material, such as koji. Temperature, humidity, and time are precisely controlled; in the past, this was done through experience and architecture, but today it is often done with the help of modern technology.

Traditional breweries and manufacturers still work with wooden buildings, clay walls, and open fermentation vessels. These environments have been home to stable microflora for generations. Fermentation here is not a sterile process, but a living dialogue with the environment.

Koji – the heart of Japanese fermentation

Koji is at the heart of this culture. This usually refers to the mold Aspergillus oryzae, which is cultivated on steamed rice, barley, or soybeans. Koji is not a food in the traditional sense, but rather a starter, an enzymatic powerhouse.

The koji fungus produces enzymes that break down starch into sugar and proteins into amino acids. Without koji, there would be no sake, miso,shochu, mirin, awamori, or soy sauce. Umami, the famous "fifth taste," would be almost unthinkable without koji. Koji can be used in many ways: to make marinades, fermented butter, chocolate, or even desserts.

Classics of Japanese fermentation

Soy sauce (shoyu): Made from soybeans, wheat, salt, and water. The koji phase is followed by a long fermentation process in brine, often lasting months or years. Regional differences arise due to raw materials, climate, and duration.

Miso: A fermented paste made from soybeans (sometimes with rice or barley). The spectrum ranges from mildly sweet, light shiro miso to strong, aged aka miso, or "red" miso.

Natto: Steamed soybeans fermented with Bacillus subtilis. The smell and consistency take some getting used to, but the nutritional value is enormous. Natto is considered one of the healthiest foods in Japan.

Sake: Japan's national drink made from rice, in which koji converts the starch into sugar, which the yeast then ferments into alcohol. A highly complex, parallel fermentation process.

Shochu: A distillate made from various raw materials, also produced with koji. Strongly influenced by regional characteristics, especially in Kyushu.

Mirin: A sweet sake with intense sweetness, the sugar consists of complex carbohydrates that form during fermentation. Indispensable in Japanese cuisine for shine, depth, and balance.

Amazake: Literally "sweet sake," but actually a mostly non-alcoholic drink made from fermented rice. Amazake is made with either koji or sake lees. Naturally sweet, nutritious, and easy to digest, it is considered a historical energy drink and is now experiencing a modern comeback as a healthy ferment.

Regional characteristics

Japan's fermentation landscape is shaped by regional differences. In cold regions such as Tohoku, saltier, longer-fermented products dominate. A refined, elegant miso culture developed in Kyoto. Nagoya is known for its dark, strong Hatcho miso. Kyushu is considered the stronghold of shochu, while the coastal regions cultivate their own fish fermentations. This diversity is no coincidence, but rather the result of local microflora, climatic conditions, and historical trade routes.

Japan's influence on the world

Many countries have adopted or further developed fermentation techniques from Japan. Koji is now used in European and American kitchens to create new flavor profiles. Modern soy sauces outside Asia are increasingly based on traditional Japanese methods rather than quick chemical processes. The idea of controlled, open fermentation—without complete sterility—is also influencing bakeries, breweries, and fine dining concepts worldwide.

What is used most frequently?

Quite clearly: koji. It is the backbone of Japanese fermentation. Followed by lactic acid bacteria and yeast. But it is not so much the individual microorganism that is decisive as the system: time, temperature, raw material quality, and experience.

Fermentation as a cultural principle

In Japan, fermentation is more than just a technique. It is an expression of a worldview that accepts change and values maturation. Nothing is ready immediately; everything is allowed to develop. Perhaps that is precisely what makes this cuisine so magical: it trusts that patience creates flavor. Those who embrace Japanese fermentation not only discover new flavors, but also a different attitude toward food—and toward time itself.