Miso Classifications Explained

Misaki Iwaki

January 8, 2023
The world of miso can be a confusing one for newcomers, but rest assured that all miso are delicious in their own right. While every miso has its merits and uses, miso fans are encouraged to try the many varieties on offer to find what works for them.
Many Japanese foods, including soy sauce, another fermented Japanese staple alongside miso, must follow the Japanese Agricultural Standard (JAS) in their creation and classification. Miso, meanwhile, has no JAS standard, and there are no clear classifications for this common Japanese food and cooking ingredient.

Reasons for miso falling outside of classification standards are numerous. There are many types of miso, for example, and it’s difficult to classify them; the yeast and lactic acid bacteria in uncooked products remain alive and consume nutrients and change in composition even after shipment, making it difficult to chemically analyze the product and come up with a standard.

Even so, loose miso classifications can help consumers decide on the best miso for them. Here are three key points to keep an eye out for:

1. Kinds of koji

Soy beans, koji and salt each in a white plate arranged in line
(From the left) Soy beans, koji and salt
Miso traditionally contains only three ingredients: soy beans, koji, and salt.

Koji, which breaks down soy beans and promotes fermentation, is an essential ingredient. Diving deeper, three types of koji are mainly used in making miso.

Rice miso, barley miso and soy miso in a white plate
(From the left) Rice miso, barley miso and soy miso
Rice koji, producing “rice miso.”

Rice miso is made from rice koji, which is composed of white or brown rice. It accounts for 80% of the market share in Japan and is the most widely shipped in the industry. It comes in a wide variety of flavors and colors.

Barley koji, producing “barley miso”

Barley miso is made using barley koji, derived from raw barley or naked barley. It is often eaten as-is and features a strong, sweet flavor. In some regions, miso soup produced from barley miso is consumed cold.

Soy bean koji, producing “soy miso”

Miso made with soy bean koji, derived from soy beans. It has a particularly long maturation period of one to three years and is believed to have numerous health benefits. This particular miso is therefor commonly used in health studies.

Mixed miso – many miso products blend the above miso bases.

Mixed miso is prized for its richness of flavor and aroma. Mixed miso containing soy miso is referred to as “aka-dashi” in many markets.

2. In addition to type of koji, miso can also be classified by its saltiness.

Miso can also be further classified based on its overall flavor. Miso generally contains a complex combination of sweet, salty, umami, sour, bitter, and astringent flavors and are classified into three main categories: ama-miso (sweet), amakuchi-miso (medium sweet), and karakuchi-miso (dry) in general miso products. These three profiles are also often used in breaking down miso categories for competitions.

More salt makes miso more “dry” on the palate, and more koji lends miso sweetness. Recently, a sweet flavor with more koji has been preferred on the overall market. Sweet miso is good for eating as a topping, and dry miso is recommended for cooking because its salty profile allows cooks to adjust salt and umami levels in a dish.

Understanding sweet vs. “dry” miso

Low 5-7% salinity sweet miso is often referred to as “shiro-miso.”

Shiro-miso (or “white miso”) is eaten in the Kansai region, and Edo sweet miso is traditional in Tokyo.

In the Kansai region, there is a culture of eating “o-zoni” New Year’s celebration soup with white miso.

7-11% salinity sweet miso is often called “amakuchi” miso and comprises most of the miso sold in Japanese supermarkets. There is a wide range in this category, combining certain levels of sweetness and saltiness.

11-13% “High Dry” miso is the saltiest of these categories. It is characterized by its clean flavor and was historically the most mainstream type of miso available. Now, it’s more of a Northern regional specialty in Japan.

Is there a “medium-dry”?

There is no unified definition, but a layman might define medium-dry as miso with a salinity of around 10% and a high koji ratio. This particular style is increasingly common. In the past, dry miso with high salt content was often produced with the specific intent of food preservation, but now that the modern preservation environment is better, the amount of medium-dry miso for table consumption is increasing.

3. Classification by color

Four different miso each in a white plate
Another classification method for miso also exists: By color. Miso is often classified into white, light, and red.

The color varies depending on the variety of soy beans used, whether the beans are cooked or steamed, the amount of koji used, the temperature control process during the fermentation and ripening process, whether or not the beans are mixed during the process, and many other factors.

Miso that has been aged for a short period are considered white, while those that have been aged for a more extended period become light (beige to yellow, in terms of actual visual color) and red, and those that have been aged for an even more extended period, although not classified as such, can also even take on a black appearance.

The Maillard reaction, seen everywhere in cooking, is responsible for the deepening of color in miso varieties. This reaction takes place between the protein in the soy beans, koji, and sugars in a miso. Shiro-miso (white miso) is made by boiling the beans to weaken the Maillard reaction so that the white color remains.

The definitions of miso’s different colors

Period of fermentation and ripening:

Shortest: Shiro-miso (about one month)
With its beautiful white color, Shiro-miso requires the shortest amount of time to mature. Generally, it has a strong sweet flavor, but there are also products with high salt content.

4-8 months: Light-colored miso
Yellow miso is distributed nationwide in Japan. Recently, it’s become more prevalent in supermarkets in Japan.The specific maturation time varies depending on the brewer and manufacturer.

More than one year: Aka-miso
Miso, aged for more than one year, becomes darker in color. Rice miso, barley miso, and soy miso that have been aged for a long time belong in this category. As mentioned above, some of these extremely dark miso can almost appear black.

The environment during fermentation and ripening also affects the color of miso.

If miso fermentation takes place in high temperatures, or if the ratio of koji in the ingredients is high, the speed of decomposition will accelerate, and the color will become darker as a result.

The darker the color, the drier the miso.

The color of miso changes with the maturation time, as described above. It is often thought that the darker the color of miso, the drier its flavors are, but the darker color does not necessarily mean a higher concentration of the individual ingredients.

The world of miso can be a confusing one for newcomers, but rest assured that all miso are delicious in their own right. While every miso has its merits and uses, miso fans are encouraged to try the many varieties on offer to find what works for them. Whether used in cooking or as a condiment, miso is versatile, packed with umami, and is a quintessential fermented product with the power to delight in many dining scenarios.

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