About Koji

– This is the RICE KOJI !!  Report of all hand process Rice Koji shop in Niigata



Miso soup for breakfast and dinner, soy sauce that always makes it on the dining table, the evening cup of sake-Japan has a wealth of fermented food products and beverages. The fermenting agent used in many of these foods is koji, a fungus of the genus Aspergillus. But in today’s fast-paced society , natural fermentation is growing rare.

An Unsung Hero in the Japanese Diet

Fermented foods and seasonings are so essential to Japanese food that virtually no Japanese meal is complete without them. The beauty of fermentation is that it enhances the flavor of ingredients and increases their nutritional value while at the same time making them less perishable. The Japanese have traditionally made full use of this technique of harnessing microorganisms to produce and preserve diverse foods. At the foundation of this culture are koji in various forms, including rice koji, barley koji, and bean koji.

The rice koji is finished after three days.

Today, unfortunately, fermented seasonings and foods made using koji face a situation in which “bad money” is on the verge of driving out good. Aimed at producing and preserving foods and beverages, the process of fermentation involves taking vigilant care of living organisms. It is a delicate task that demands much time and close attention. But with the advent of rapid economic growth in the mid-1950s, most of the companies in Japan’s food manufacturing industry cast off laborious methods of fermentation and switched to automated fast fermentation under the mantra of “faster, cheaper, and more.” Mass production of widely used foods by fast fermentation led to the emergence of national brands in the brewing industry. Inexpensive fermented seasonings, sake, and the like became available anytime, anywhere, and to anyone, but at the cost of the subtle flavors and rich nutrients of naturally fermented products. Things that meant less hassle and less time spent in household duties were welcomed in the home as well.

The pursuit of speed thus penetrated even the area of food, so basic and vital to our lives. The upshot has been a trend away from home cooking, excessive dependence on the food service industries, and changes in the Japanese palate caused by frequent use of chemical additives. These, in turn, have brought on grave changes in Japanese home and local cuisines. Regular consumption of fermented foods has been a factor behind the long life spans that the Japanese enjoy, but this dietary habit is now eroding.

A Secret and Sophisticated Tradition

Given this situation, it seems apropos to turn the spotlight on koji-what it is, how it is made, and how the tradition has been handed down. To begin, a few terms are defined below. The word koji can refer both to a fungus and to a food ingredient that is commonly made using rice, barley, or soybeans.

  • Tane koji, literally “seed koji,” are the spores of the fungus Aspergillus oryzae. The fungus is a type of mold that is native only to the humid Southeast and East Asian regions.
  • Koji is made by sprinkling tane koji over steamed rice, barley, or soybeans and cultivating the fungus under temperature conditions suitable for its growth. As the fungus propagates, enzymes break down the grains’ starch and proteins into sugars and amino acids.

Koji can take on a variety of characteristics depending on what kind of seed koji and grains are used to make them. Different koji are employed for different fermented foods, such as soy sauce, miso, sweet rice wine, vinegar, shochu (a distilled alcoholic beverage), amazake (a sweet, mildly alcoholic drink), and pickles. In fact, even with sake alone, the koji for brewing premium sake and the koji for brewing regular sake are made with distinct types of seed koji, as well as distinct types of rice. Highly polished rice is used for the former and less polished rice for the latter.

Seed koji are distributed in the brewing industry by seed koji dealers, who are versed in the qualities, aptitude, and uses of each. The ancestors of the dealers were the jinnin, who served in shrines. Nearly six centuries ago, in the early Muromachi era (1336-1573), the shogunate exempted these people from a tax that was usually levied on those making koji. The jinnin soon formed a union in Kyoto known as the Koji-za, which enjoyed a monopoly on the production and sale of koji in and around the ancient capital.

Producing and storing seed koji require special skills that have been handed down through the generations in the family business. That knowledge has been kept strictly secret by each dealer, making it exceedingly difficult for other industries and newcomers to enter the business. Consequently, only a dozen or so dealers exist in all of Japan.

*Text from Tokyo Foundation*

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