What Is Natto? Ask Paul

Natto is a traditional treat from Japan, consisting of briefly fermented soybeans coated in a stringy, sticky goo. Like soy sauce and miso, it develops complex savory flavor through the action of beneficial microbes.

Unlike soy sauce and miso, which are widely accepted outside Japan, natto hasn’t caught on globally in the same way. 

Natto has been slow to catch on because it has a strong flavor that’s not always easily appreciated: malty, cheesy, sweaty, bitter, and sometimes ammoniacal, like a washed-rind cheese. But more than that, the characteristic that has made it famous on social media is the long, slippery strings of goo that develop in natto during fermentation.

A species of bacteria called Bacillus subtilis, also known as nattokin, is responsible for turning steamed soybeans into natto. During just 18 hours or so at around 100°F, the bacteria break down the beans’ protein into savory amino acids and its fat into buttery, cheesy flavor compounds. They also produce long, gooey chains of polysaccharides (like those in okra) and polypeptides.

In the eyes of natto appreciators, this goo is the point. According to a 2001 Journal of Food Science article, “[S]ilky stickiness feeling due to a high viscosity of the mucilage is the most important criterion of a good natto.” The Japanese term for this texture is “neba-neba”.

Stirring natto before eating it helps the mucilage strands stretch and link up: The more you mix, the more strings of goo you get.

The classic way of eating natto is simple: natto over rice, dressed with soy-based sauce, scallion, and/or a little mustard. That simplicity allows the flavor—and texture—to shine. But for natto novices who want to start with a less natto-forward preparation, it’s awfully good mixed into scrambled eggs: Stir a 2-ounce packet of natto into three beaten eggs with a pinch of salt and then fry and top with chopped scallion.

Once you get to know natto, it becomes extremely craveable. The Western culinary aesthetic has an endless appetite for long strings of stretchy cheese, so why not natto? Anyone for natto nachos?

Natto can be bought refrigerated or frozen at Japanese food markets and is also easily found online.

Store-bought natto typically comes frozen in little polystyrene boxes containing individual servings, often with a plastic packet of optional sauce. If you’re curious, or eat a lot of natto and get tired of tossing out all the packaging, it’s very easy to make your own in a multicooker.

• Cook 1 pound dry soybeans in pressure cooker mode until tender.
• Drain and allow to cool to 100°F or less.
• With a clean spoon, mix in one packet of store-bought natto or powdered natto starter culture.
• Close the pot and set it to 100°F for 24 hours.
• After 24 hours, refrigerate the natto for another 24 hours.
• Enjoy.

Advanced fermenters may want to use a home-built fermentation chamber for this and all sorts of other projects.

_{Photo: Nattō (aka rotten soybeans) by JD is licensed under CC BY 2.0, modified by Rose Flynn}