We made natto!

Upon arriving in his laboratory four days ago, Shen Lirong, the professor I am working with, announced that I would be making natto. I think it was a preliminary experiment so that I could get used to the equipment in his laboratory, but the language barrier between us is such that I can never be completely certain.

Natto is a traditional Japanese food, which is made by fermenting steamed soybeans with the bacillus subtilis var. natto bacteria. The result is a slimy, sticky mass of soybeans, which has a pungent odor that I liken to a mix of snot and permanent marker. Natto is chock-full of nutrients and good probiotic bacteria, and many attribute regular consumption of natto as one of the reasons why the Japanese have such long lifespans. However, most likely due to its unusual taste and mucus-like consistency, natto has not gained a foothold in the American palette, or Chinese palette, for that matter.

While I’m skeptical of calling anything a “superfood,” natto comes pretty close to deserving that moniker. Natto is one of the few foods that is high in Vitamin K2, a vitamin which has been linked to promoting healthy muscle function and bone strength. Additionally, natto contains a special enzyme called nattokinase, which is not found in any other foods. This enzyme has been directly identified as having fibrinolytic properties— in other words, nattokinase helps reduce blood clotting and helps prevent heart disease. Not to mention it is a live-culture food, so it also contains all the health benefits of eating foods with probiotic bacteria.

It was a rather strange experience using test tubes and fume hoods in a laboratory to make food—I distinctly remember one of the main tenants in high school chemistry lab was NO FOOD IN THE LABORATORY. Natto can be made in your home as well, but I’m glad that we made it in a laboratory for the first time, because even a little bit of bacterial contamination, from, say, your fingers, can make the whole batch go bad.

We began by mixing salt, yeast, and a peptide mixture called tryptone, which in addition to the yeast is another type of “food” for the bacteria to feast on. After dissolving the mixture in water, we steam-pasteurized it, as to kill any bacteria floating around. Next we added the bacillus subtilis var. natto culture to half of the mixture, and a bit of previously made natto to the other half of the mixture, as to compare results.


In come the soybeans. After soaking the beans for 24 hours, and washing the thoroughly, we put them in the steam pasteurization machine, as to simultaneously rid them of bacteria, and also to cook them! Traditionally, the beans are steamed for around 6 hours, but since our machine was at a constant temperature of around 150°C, the beans took around 45 minutes to cook through.

After adding the yeast mixture infused with our two mediums of bacillus subtilis var. natto (one liquid, one from the previously made natto), we put them in the oven to ferment at a lower temperature— around 33°C, I believe— and set the clock for 24 hours.


Upon arriving at the laboratory on Sunday, the natto was ready to be eaten! Mixing it with a spoon produced the long, sticky strands that are characteristic of natto. I brought half of the batch home to the family I’m staying with and we ate it for dinner with our rice and other vegetables. It’s a few days later, and we’re all still alive, so I think the natto was made correctly! I look forward to making natto back in the states— when eaten with rice and some soy sauce, it’s satiating, very umami, and delicious.



One thought on “We made natto!

  1. “even a little bit of bacterial contamination, from, say, your fingers, can make the whole batch go bad.” Given how awful it smells, how can you tell if it has gone bad?


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