Making Miso and Soy Sauce in the Shadow of Zenkoji Temple

Shinshu, the ancient name of modern-day Nagano Prefecture, is one of the best brewing and fermenting areas in Japan. Kuze Fuku & Co.’s main store near Nagano’s Zenkoji Temple is surrounded by a number of sake breweries and miso warehouses, dating back to Japan’s Edo Period. One of these, Mihara-ya, has been making miso in the area for over 170 years, and are experts in making koji, the fermentation starter used in miso, soy sauce and other fermented foods and beverages.

The Basics of Miso Making

When it comes to the everyday challenges to continue to overcome when making quality miso, Kiyotaka Kawahara, owner of the 6-generation Mihara-ya, says, “The technique is really a matter of whether or not we can bring out the best of the ingredients we have.” Mihara-ya began business as a rice wholesaler, while also producing koji, a fermentation starter made from rice and used in the fermentation of soybeans for miso and soy sauce. Going with the flow of the times, Mihara-ya slowly changed over the years into a miso and soy sauce production center and warehouse, while gradually developing and improving the craft along the way.

Koji is born of Rice

Koji is actually a mold, and its domestication in Japan dates back over two-thousand years. To make koji, rice is first steamed and then after cooling down, the koji is seeded and cared for, in a process that takes 44 hours. Eventually, mycelial growth will dig into the center of the rice grain, a development known among koji makers as “hazekomi,” thus completing the creation of koji.

When finished, koji has a fruity, sweet and sour aroma. It is used in the production of sake, miso, soy sauce, mirin, black vinegar, amazake and other products. It contains lot of digestive enzymes.

In recent years, scientific studies have suggested that eating fermented foods, including those made from koji, has the effect of causing the body to absorb more nutrition, while enhancing the taste of the ingredients and aiding with digestion. Yet the makers of koji have known of this long before such studies were ever conducted.

Important Factors in Koji Making

Mr. Kawahara stresses the importance of what he calls “emotion backed by experience.” As examples, he explains that qualities like the richness of fragrance are an important point in determining whether the fermented food will be of good quality or not; that people tire quickly of a food lacking an interesting or surprising flavor; that the creator with a good sense of what makes food delicious would be able to almost instinctively produce a product that fits into the range of what consumers want.

After trying the soy sauce and miso at Mihara-ya, it is clear they have mastered this careful balance between experience and sensitivity.