味噌の歴史と発酵・健康Miso: Fermentation, History and Health

Miso, drawing attention today from the viewpoint of probiotics, is one of Japan's representative traditional seasonings, made by fermenting soybeans with salt and koji. Made with fermentation technique accumulated over history, miso is not merely a main element of Japanese cuisine; like yogurt and kimchi, it holds the potential to contribute greatly to modern health. Miso contains vitamins, minerals and protein in good balance, and in the course of fermentation in particular it produces functional components such as antioxidant action, aid to digestion and strengthening of immune function.

Further, unpasteurized miso is rich in probiotics such as lactic acid bacteria and yeast, and draws attention because it works to put in order the gut environment, a problem of modern humanity. Yet, though miso is a fermented food indispensable to modern health promotion, the future of miso in Japan is in fact not so bright.

Looking back first at the history of miso, no trace has been found to this day that miso was eaten in ancient Japan, in the Jomon period for example. Written records on miso go back to the early eighth century. The Japanese court of the time adopted the system of China, by which it was greatly influenced, and the Taiho Code (701), Japan's oldest legal code, enacted then, has a record of miso.

The word “miso” (味噌) is not yet used in this text; it is recorded as “misho” (未醤). Still, it is a seasoning made from fermented soybeans, hardly different from today's. Miso of this age was influenced by China's hishio (醤), so we can see that the roots of Japanese miso lie in China.

Interestingly, the Taiho Code already made miso taxable. That is, at least before then miso had come to Japan and was widely involved in Japanese life. On the other hand, the miso of this age was basically a limited food culture eaten by aristocrats and monks, and may not yet have reached ordinary people. Miso is presumed to have begun to permeate the life of ordinary people around the thirteenth century. The basis is the Azuma Kagami (吾妻鏡, around 1300), the first history by samurai, compiled by the shogunate of the time.

The Azuma Kagami is an important text that records in detail the eighty-seven years from 1180 to 1266, and it describes samurai carrying miso when they traveled and using it constantly. This was an age when wars multiplied across the country with the rise of the samurai, so fermented miso came into wide use as preserved food on the battlefield and was quite widespread. Once a warrior went to a battlefield he could not return home for a long time, and securing food was an important factor in deciding victory or defeat. Miso, a preserved food rich in nutrition, was prized.

Besides this food culture of the samurai, another occasion for miso to spread was the spread of Zen, which became active in this age. Zen monks established and advocated a new style of eating, “one soup, one dish” (ichiju issai), and in this age miso soup became the daily food of monks. Under the influence of this plain, minimal Zen way of life, miso greatly affected the food culture of ordinary people who were not wealthy. Miso spread, then, as a portable food in an age of more travel, carried by samurai and Zen monks, not aristocrats, and became widely common. This means about 1,000 years have already passed since miso spread in Japan.

Miso came to be made across the country, but as a fermented food it varies greatly with the “climate of the place” where it is made and with “the maker.” This is because the “microbes” that the land and the person hold are the key when miso ferments. Most miso today is mass-produced, but when I travel to various places and eat the miso of people who still make it by hand, I feel the taste is entirely different. That is, unless you choose miso that suits your own body, you cannot expect great health benefits, and you must take into account that it may even make things worse.

Particular care is needed with miso produced by modern methods. Traditional fermentation, as noted, uses the climate of the place (natural environment, weather and so on) and ferments and ages over years. From this “umami” (旨味) arises and excellent miso results. Aging miso is patient work taking from half a year to more than a year; the further fermentation goes, the darker the color and the more complex the flavor. It is not suited to mass production, and because the result varies greatly with the season and environment, it takes effort to manage and cannot keep up with a modern lifestyle. Miso made by the traditional method in particular is a “living thing” (a state in which microbes are alive), so its taste and color change during the keeping period after purchase, and its shelf life is shorter than with modern methods.

Modern methods, on the other hand, made mass production possible by promoting fermentation with temperature control and mechanization. Aging can be finished in about four to six months with heat treatment, roughly half the period of the traditional method, and factories have the advantage of managing with steady quality and little variation in taste. But the miso of the traditional method is “living miso,” while modern miso is heat-sterilized before completion to stop fermentation, so useful microbes such as koji mold and lactic acid bacteria die. In addition, since fermentation is finished in a short time, the health benefits from living microbes as a fermented food cannot be expected. Compared with traditional “long-aged miso,” therefore, the taste quality and health benefits of modern miso may not be expected.

In fact, most of the miso used in Japanese restaurants and supermarkets is this “sterilized (heat-treated)” product. Because this sterilizing process loses even beneficial microbes such as yeast and lactic acid bacteria in the miso, it should be noted that almost none of the effect as the probiotic food now drawing attention is obtained. Moreover, in the simplified eating of today, even when “living miso” is used, miso is added to boiling soup, so the living microbes (lactic acid bacteria in particular) die and the effect is lost. The key to making miso soup is to add the miso after turning off the heat. This was commonly known wisdom up to my grandmother's time, but many people now do not know it. With this small practice you can enjoy miso soup that makes use of the power of fermentation.

If you have the chance to stay in Japan for a long time, I think it would be a good experience to set out on a journey to look for the handmade miso still being made in various places, rather than going to restaurants and supermarkets, and to find the miso that suits you.