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Our Feature series this year has introduced various fermented foods of Japan that are considered indispensable to Japanese culinary culture.
This final article focuses on sake, mirin and rice vinegar.

Sake

Foods and wine produced in the same cultural milieu naturally complement each other. Just as grape wines go well with French cuisine, so is sake or nihon-shu (rice wine) the best companion to Japanese dishes.

Unlike other liquors, sake plays a special role in Japanese culture as a sacred offering to the gods. This fermented drink is believed to have been introduced to the Japanese archipelago at around the same time as the practice of rice cultivation. The basic brewing techniques were apparently developed over 1,000 years ago, and the prototype of the brewing methods used today had been established by the late sixteenth century.

The principal ingredients of sake are rice, water and rice koji (fermentation starter). The basic process of sake brewing involves steaming the rice, preparing koji and cultivating shubo (yeast starter), followed by a multi-step fermentation process. Following this, the sake undergoes filtration, heat treatment (such as pasteurization) and storage.

The three most important of these steps are, in order of precedence, cultivating koji, preparing the yeast starter and fermentation. The rice koji provides the enzymes that break down starch into sugar molecules. Koji is cultivated by sprinkling a fungus called Aspergillus oryzae on steamed rice, which is then stored in a special room (koji muro) where temperature and humidity are regulated.

Next, the yeast starter, which initiates ethanol fermentation, is mixed with cold water. Steamed rice is then added to the mixture and stored at a low temperature to cultivate lactobacillus and yeast. Finally, the mixture goes through a three-fold fermentation process, with varying ratios of rice koji, steamed rice and water. Sake is thus produced by two simultaneous processes: ethanol fermentation and the saccharification of starch molecules in the rice.

Sake production begins after the autumn rice harvest and continues throughout the winter. Production is overseen by a master brewer called the toji, and when it comes to the sake being brewed, the toji’s authority exceeds even that of the owner of the brewery.

One of the main ingredients in sake is rice. Brewers use a particular kind of rice grown especially to make sake, which differs from the rice that is the staple of Japanese meals.

An even more important ingredient in the brewing of sake is the water. Brewing water generally contains very little iron and manganese, and is categorized as moderately hard water according to the American measurement scale that determines the degree of mineral concentrations in water. Ideally, brewing water has a higher mineral content than the average drinking water in Japan, and includes potassium, magnesium and calcium, making it well-suited to the cultivation of koji fungus and yeast. As a result, many brewers even relocate in search of superior water. Probably the best-known water for brewing purposes is Miya mizu (Miya water), found in a particular area of Kobe.

Ultimately, sake boasts a clear, pure-brewed quality that is rare among domestic and foreign liquors. It has a distinctive aroma, and can have an alcohol concentration of over 20 percent.

Today, there are some 1,700 sake breweries throughout Japan. Most of these are small-to medium-sized, and because of this a wide variety of sake is produced. In fact there are over 15,000 varieties of sake, each of which has its own unique appeal.

Mirin

Mirin is a sweet and fragrant amber liquor. In the late sixteenth century, mirin was popular among the upper classes who enjoyed it as a sweet sake or liquor. Its culinary uses gradually spread, however, and today it is produced almost exclusively as a flavoring used in cooking.

Mirin is made from glutinous rice, rice koji and shochu (distilled spirits). The addition of the shochu suppresses ethanol fermentation, and thus large amounts of sugars and amino acids are created which trigger an aminocarbonyl reaction during the maturation period. This reaction gives mirin its distinctive amber color. Its flavor mellows and its color turns darker during longer maturation periods.

Mirin is a popular flavoring with various uses—among them as one of the primary flavorings in simmered dishes (nimono). Mirin gives Japanese dishes a subtle sweetness and sheen, helping ingredients to absorb flavor while eliminating unpleasant meat and fish odors. Mirin and soy sauce together provide an enhanced luster to foods and are used in teriyaki sauces for fish and meats.

Rice Vinegar

The other fermented product essential to Japanese cuisine is rice vinegar (su). Called yone-su or kome-su, this vinegar is made from rice and rice koji in a process similar to that of sake. It is widely used in the preparation of sushi rice.

Unlike vinegars made from wheat or corn, which have a more biting, sour taste, rice-based vinegar is known for its mild, umami-rich flavor. Versatile and complex, Japanese rice vinegar is used in a variety of dishes besides sushi, and is a major ingredient in Japanese cuisine.

These three rice-based fermented foods—sake, mirin and rice vinegar—have deep roots in Japan’s diet and have played significant roles in shaping its culinary culture. The fermentation processes of these products have been practiced by generations of professionals whose techniques have sustained Japan’s fermented food traditions.

Author's profile

Hisakazu Iino was born in 1952. A 1975 graduate of the Tokyo University of Agriculture, since 1997 he has been a professor in the Graduate School of Science for Living Systems at Showa Women’s University. As a specialist in applied microbiology, Dr. Iino studies the interaction of human intestinal microorganisms. He also serves as an advisor to the Pharmaceutical Affairs and Food Sanitation Council, Ministry of Health, Labour and Welfare.