Tasting White Miso Paste

In the test kitchen, we generally use two styles of miso: white (shiro) and red (aka). White is fairly sweet and mellow, while red tends to be more robust and salty. We call for white miso more often than red, so we decided to focus there first. Curious which products would deliver the best flavor, we purchased five widely available white miso pastes priced from $4.80 to $7.49 per package ($0.34 to $0.92 per ounce). Panelists sampled them in three blind tastings: plain, in miso soup, and in a marinade on broiled salmon. Throughout, we evaluated the flavor and overall appeal of each product.

As authors William Shurtleff and Akiko Aoyagi explain in The Book of Miso (1977), the first step in making miso is cultivating a mold called koji (Aspergillus oryzae), which is also a crucial component of soy sauce, sake, and fermented black bean paste. (It’s not unlike the unique molds used to make blue cheese and Camembert.) Tiny spores of koji are typically sprinkled over cooked rice and spread across special trays in a carefully controlled environment. There, they incubate for two or three days as the rice ferments and the koji germinates.

Next, the koji is mixed with cooked soybeans, salt, and sometimes water. Here, different varieties of miso paste diverge; producers can adjust the ratio of koji to soybeans to alter the flavor profile. The mixture is left to ferment as the koji produces enzymes that break down the proteins, carbohydrates, and fats in the soybeans. One type of enzyme, called protease, converts the main protein in soybeans to amino acids, including glutamic acid, the source of miso’s trademark umami flavor. At the same time, other enzymes break down the starches into simple sugars, which adds sweetness. Though some kinds of miso ferment and age for as long as two years, white miso is ready for packaging in just a few weeks or months.

The miso pastes in our lineup varied dramatically in appearance. Despite their name, none are actually white. Some were a dark toffee color, and others were a light golden brown. The majority had a smooth-chunky texture that reminded us of freshly ground peanut butter. One outlier, sold in a squeeze pouch instead of a plastic tub, was noticeably smoother and softer than the rest.

Even though it’s one of the mildest types of miso, white miso paste is very complex stuff. Flavor differences among the products were most apparent in the plain tasting, though trends persisted throughout. Most were “deeply savory” and “umami”-packed. Some tasted “funky” and “fermented,” with distinctly “nutty” and sweet, roasted flavors of “browned butter” and “caramelized” sugar. One “fruit-forward” miso drew comparisons to “mango,” “banana,” and “pineapple.” Some were mildly salty, others intensely so. One was sweeter than the rest. Our favorites struck the “perfect balance” of salty, sweet, and savory.

We set out to learn more about the differences among the products, and our first discovery was simple: Color wasn’t a good indication of the strength of a miso’s flavor; the darkest products didn’t necessarily have bolder flavor than the lighter ones. One thing that did matter was the salt level. The highest-sodium misos sometimes tasted “olive-like” or “briny” and came close to overwhelming other ingredients. Another product wasn’t quite salty enough. The sweet spot, we found, was between 550 and 675 milligrams of sodium per 15-gram serving.

The lowest-sodium miso was also the sweetest, which is no surprise given that it’s the only one that contains a sweetener: malted sweet potato extract. The combination of less salt and the extract meant it tasted much more “mellow” and “sweet” than the rest of our lineup. Some tasters thought the mildness allowed other ingredients to shine, but most on our panel preferred more full-flavored products.

Koji is listed on the packaging of only two products in our lineup; however, all the manufacturers told us that they use the mold to make miso. They explained that they don’t mention koji for a variety of reasons, including that it isn’t well understood in America and that it’s considered a “processing aid,” so it’s not required to be listed on the label. 

Other obvious production differences—the length of fermentation and whether misos were domestic or imported—didn’t seem to have a bearing on the rankings. All the products we evaluated are aged for six months or less, with most in the one-to-two-month range, and we didn’t have a clear preference for older or younger products. The second- and third-place miso pastes were made in America; the rest were produced in Japan. Ultimately, we think that the key to a full-flavored yet balanced white miso paste is a combination of proprietary factors, including the individual strain of koji used and the specific ratio of koji, soybeans, and salt.

We’re generally pleased with the range of white miso pastes available at Asian markets and grocery stores, and despite subtle flavor differences, all five products in our lineup made good miso soup and salmon. In the end, each earned our recommendation, but tasters did have a favorite: Hikari Organic White Miso ($0.43 per ounce) has a “caramelized sweetness” and plenty of “funky,” “fermented” flavors to balance its moderate sodium level. A small amount of this miso paste adds intense, complex flavor to miso soup, vegetable dishes, sauces, dressings, and more.