Natto With Rice

Natto is a traditional Japanese food made by fermenting soybeans with a starter culture, Bacillus subtilis. Unlike lacto-fermented foods such as kimchi and sauerkraut which are preserved through acidification, natto is an alkaline ferment. 

What Does Natto Taste Like?

Alkaline fermentation leads to natto’s unique flavor profile, often described as nutty or earthy. Some people also detect a note of pleasant bitterness, like coffee.

The fermentation process is also responsible for natto’s signature stickiness. As you stir natto, you will notice the strong spider web-like strings that form between the beans. The smell of freshly made natto can be quite mild, but as it ages in the refrigerator it becomes stronger and more ammonia-like, somewhat similar to ripe cheese.

The Origins of Natto

The exact origins of natto are not known. One legend has it that a samurai was cooking soybeans, but was then suddenly called to battle. He quickly wrapped his hot soybeans in straw and tied them to his horse’s warm side, where they remained throughout the battle. Afterwards, he opened the packet to discover a tasty, sticky treasure.

More on Bacillus Subtilis

Bacillus subtilis, the bacteria used to culture the soybeans, thrives seasonally on straw (and tatami mats, the traditional Japanese flooring made of straw). It’s easy to imagine freshly cooked soybeans interacting with straw—either as part of some quiet culinary experimentation or by accident—paving the way for natto to become a part of the Japanese diet. In fact, alkaline bean ferments are found in other parts of Asia and in West Africa where similar bacteria are abundant.

What Are Soybeans?

Types of Natto

The natto section in a Japanese supermarket offers many choices. Most are made with a variety of yellow soybeans that are slightly smaller than those typically seen in North America, while others are made with black soybeans. Another type of natto, hikiwari, is finely chopped. Usually included in the natto package are a soy sauce-based flavoring packet along with a packet of hot mustard, both of which may be stirred into the natto.

Preparing Natto for Eating

Folk wisdom holds that stirring is an essential first step in preparing natto. Stirring increases the flavors and makes the natto even stickier. How long to stir and when to add flavoring is a matter of preference. I stir for about two minutes by which point the natto has become white and frothy. Adding any sauces at this point tempers the frothiness.

How To Eat and Flavor Natto

As a rule of thumb, think about flavoring natto with something creamy, something salty, and something acidic. One of my favorite non-traditional ways to serve natto is to chop equal parts natto and kimchi and mix them together, then serve atop avocado toast.  

Natto is typically enjoyed at breakfast alongside rice, miso soup, pickled vegetables and grilled fish. People who eat a traditional Japanese breakfast likely have a small portion of natto (1 to 2 ounces) most days. Chopped green onions are a usual topping as is a raw quail egg.

Natto is often described as an acquired taste. I first encountered natto in my early twenties and it was love at first bite. Many people who don’t like natto at first soldier on, due to its potential health benefits. In my experience it doesn’t take too long for people to find their own favorite way to prepare natto. If, however, the viscosity remains an issue for you, incorporating unstirred natto into oatmeal or soup may offer a way forward.

Cooking destroys the probiotic bacteria in the natto, but adding it when serving does not. For example, try adding a dollop of natto to a serving bowl, ladle in miso soup, and then gently stir.

Making Natto at Home

If you cannot find natto locally, or if you’re just up for a fermentation adventure, it’s possible to make it at home.  Directions can be found online and in “Miso, Tempeh, Natto,” by Christopher and Kirsten Shockey.

How To Store Natto

Natto has a short shelf life, but it can be frozen to preserve it longer. Most natto sold in the United States comes from Japan and is often sold frozen for this reason. Once defrosted, it’s best eaten within a few days.

Natto and Nutrition

In addition to its probiotic content, natto has a number of other notable attributes. It’s the highest source—and the only significant plant based source—of Vitamin K2. Nattokinase, an enzyme unique to natto, is produced during fermentation as is PQQ or pyrroloquinoline quinone. Vitamin K2, nattokinase, and PQQ are of great interest to researchers studying nutrition and human health.