White Miso vs. Red Miso: What to Know
White miso and red miso are color labels, not recipes. White miso is a pale, sweet rice miso, while red miso runs from sweet to salty, so check the style name on the tub as well as the color.
The English words "white miso" and "red miso" are color names. Japanese Taste says white miso is known as shiro miso in Japanese, and red miso as aka miso. Marukome USA says miso is "visually categorized into red miso, light-colored miso, and white miso according to the finished color." The word on the label names a finished color, not one fixed recipe.
Neither color is better. MAFF, Japan's agriculture ministry, sorts rice miso into three salt styles. White miso appears in only one of them, and red miso appears in all three. So two tubs that both say "red" can sit at opposite ends: one sweet, one salty. Look for a style name next to the color to tell which end you are holding.
How Miso Color Works
MAFF says miso is made by mixing koji and salt in steamed soybeans. Koji is rice, barley or soybeans grown with koji mold, and JETRO calls it a fermentation starter. The grain in the koji sets the base: rice koji makes rice miso, and barley koji makes barley miso.
The Umami Information Center names the main reason for the color difference: the aging period. It says, "The longer miso is left to age, the darker its color becomes through the Maillard reaction." Aging is the main reason, not the only one. The same source also lists the soybean variety, boiling or steaming the soybeans, the amount of koji, the fermentation and aging temperatures, and whether the miso is mixed.
Sweetness depends partly on the koji rate. Marukome USA says the koji rate is the ratio of rice or barley to the soybeans. It adds, "If the salt content is held constant, the higher the koji rate, the sweeter the miso will be."
Color can keep changing after you buy the tub. Marukome USA says miso changes color over time and according to the temperature, and that this can happen even in an unopened pack. It traces the change to a reaction between sugar from the rice and protein and amino acids from the soybeans. Stored in a hot place, the color gets darker.
The words on the label
- Shiro miso: The Japanese name for white miso, as Japanese Taste gives it.
- Aka miso: The Japanese name for red miso, as Japanese Taste gives it.
- Koji: Rice, barley or soybeans grown with koji mold, used as the fermentation starter for miso.
- Ama-miso: The rice miso style MAFF glosses as sweet miso, made in white and red.
- Amakuchi-miso: The rice miso style MAFF glosses as mildly salty miso, made in light-colored and red.
- Karakuchi-miso: The rice miso style MAFF glosses as salty miso, made in light-colored and red.
- Saikyo miso: A white ama-miso from Kyoto, one of the well-known examples MAFF names.
White Miso
MAFF describes white ama-miso as clear light yellowish-white, with a distinctive flavor that comes from rice koji. It names Saikyo miso from Kyoto, Sanuki miso from Kagawa Prefecture and Fuchu miso from Hiroshima Prefecture as well-known examples. Marukome USA says white miso is also a type of rice miso. So on an ingredient list, look for rice next to the soybeans and salt.
The Umami Information Center says Saikyo miso has a very high ratio of rice koji and strong sweetness. It also describes white miso as a miso with a shorter fermentation period.
The Umami Information Center also says Saikyo miso is indispensable for kaiseki, a cuisine that developed along with the tea ceremony. It also says Ozoni, a New Year's soup, is eaten with this white miso in the Kansai region. If a recipe names Saikyo miso, reach for a tub labeled white or shiro rather than a red one.
Red Miso
Red is the wider category. In MAFF's list, red rice miso appears in all three salt styles: ama-miso, amakuchi-miso and karakuchi-miso. MAFF also says barley miso has two types, light-colored miso and red miso. A red label alone does not tell you the salt level.
At the sweet end, MAFF describes red ama-miso as brownish-red and glossy, represented by Edo-style ama-miso. The Umami Information Center says Edo sweet miso is made with plenty of rice koji over a short period of up to 10 days. It lists Dojo-nabe, a pond loach hot pot, among the Edo dishes that use it. So a red color does not always mean a long aging period.
At the salty end sits karakuchi-miso, which MAFF says is made over a long brewing period. MAFF names Shinshu miso and Sendai miso as representative of this type. The Umami Information Center calls Tsugaru miso a strong red miso aged over a long time, with a low ratio of koji-mold and high salt content.
For miso soup, either color works. The Umami Information Center says that whether miso is white or red, all of the miso varieties can be used in miso soup. When a tub names Sendai or Shinshu, read it as the salty karakuchi side of MAFF's list. If you swap a salty red in for white, start with less paste and taste before adding more. For tubs of each color with specs confirmed on the shop page, see The 5 Best Japanese Miso Pastes for Your Kitchen.
FAQs
Is red miso saltier than white miso?
Not always. MAFF places white miso in the sweet ama-miso style, and red miso in the sweet, mildly salty and salty styles alike. A red karakuchi-miso is in the salty style, while red Edo-style ama-miso is in the sweet one. Read the style name, not only the color.
Can I use white miso instead of red miso?
For miso soup, yes. The Umami Information Center says all miso varieties, white or red, can be used in miso soup. If the recipe was built on a salty red miso, taste as you go and adjust the salt.
Why does miso get darker over time?
Marukome USA says miso changes color over time and according to the temperature, even in an unopened pack. A hot place makes it darker. Marukome USA advises storing miso in the refrigerator or freezer to preserve its flavor.