How to Make Natto, Japanese Superfood

I’ve been thinking about making natto for years, but the implementation kept getting put on the back burner. This could be because there was never a shortage of fermentation projects around my house.  After my mom was diagnosed with renal artery stenosis (weighing a whooping 120 pounds on a heavy day, with zero other risk factors), I started doing a lot of research about cardiovascular health. I also wanted to learn what supplementation might be beneficial to go along with a gazillion medications she had to take in order to keep her blood pressure somewhat controlled.

One of the first things that came to my attention was Nattokinase, a supplement used to reduce blood pressure (source) and help control atherosclerosis, among many other things. There is good evidence that Nattokinase can treat progression of atherosclerosis and maybe eventually recommended as an alternative to statins (source). Of course, the next question was – where does Nattokinase come from? And that brought me right back to Natto.

WHAT IS NATTO?

Natto is a traditional Japanese food made of cooked soybeans fermented with the help of a probiotic strain Bacillus Subtilis. Soybeans ferment at warm temperature of around 100ºF for 24 hours. Fermentation results in stringy and slimy coating around the beans and a funny, stinky cheese smell that might be an acquired taste. I personally think the smell resembles most fermented vegetables, and I actually find it pleasant. The taste is like unsalted navy beans, very mild and with pleasant lush texture. Natto is a staple breakfast food in Japan, often served with a bowl of rice, soy sauce, spicy mustard and raw egg. I found that it can be mixed with just about any grain and condiment to make a super easy meal.

NATTO IS EXTREMELY NUTRITIOUS (source)

Natto is high in protein and fiber, and it’s worth noting that natto protein is already predigested via the fermentation, and is readily available for use by your body. Natto is full of vitamin C, calcium, iron, magnesium, potassium, etc.  And of course, natto is the only source of nattokinase. How many other foods can boast such an impressive lineup?

NATTO’s TRUE SUPERSTAR IS VITAMIN K2!

Natto is an outstanding source of vitamin K2. This vitamin helps with blood coagulation, maintaining cardiovascular health and strong bones. Green plant foods contain vitamin K1, which we convert into K2 inside our bodies with the help of our intestinal flora, provided that we have good dietary habits. We can also get some K2 from meat, but no animal or plant products come even close to the amount of K2 found in natto (source). Another cool thing about it is it has no toxicity since we do not store it in our liver. So you can’t have too much of the good stuff!

NATTO IS A GREAT SOURCE OF PROBIOTICS

If you are not impressed by natto so far, consider this – natto is full of Bacillus Subtilis, a perfect probiotic, which thrives in low PH environment (stomach) and easily reaches your colon. It is also a tough probiotic and can survive pretty harsh conditions because it can encapsulate itself with a protective endospore (source). Bacillus Subtilis can stimulate immune system to produce a number of antibodies, which help protect you from gut and urinary tract diseases. According to Wiki, Bacillus Subtilis was used as an antibiotic before actual antibiotics were invented.

FERMENTING NATTO – DOES IT NEED OXYGEN?

Not necessarily! Even though Bacillus Subtilis is classified as aerobic bacteria (need oxygen to proliferate), it looks like it does just fine without any air at all (source). So whether you close the lid tight, like Cultures for Health suggests, or leave air vents, like a lot of online natto recipes recommend  – you would still walk away with a batch of nutritious natto. In this post, I follow the Cultures for Health recipe.

SOYBEANS FOR NATTO

I use regular organic soybeans I get at the bulk section of Whole Foods Market. More traditionally, natto is made with small soybeans. I couldn’t find any that were organic so I went with the larger ones. The health benefits of both kinds of soybeans are the same.

HOW I LIKE TO EAT NATTO

My favorite way is to mix it with grated horseradish, green onions/chives, micro greens and some mustard, with a side of soft boiled egg. I often add sauerkraut as well. It goes really well with quinoa and a splash of soy sauce. My mom, who has to limit her salt, adds balsamic vinegar. Basically, natto is so universal that you can improvise all you want!

HOW TO MAKE NATTO

Ingredients
2 lbs dried organic soybeans
Filtered water for cooking soybeans
1 tablespoon sterilized water (boiled for 5-10 mins, then cooled)
0.1g Nattomoto powdered culture (1 special spoon that comes in a box)

Equipment
Pressure cooker (I use InstantPot)
Large sieve
Large stainless steel spoon
Cheese cloth
4 ovenproof glass containers with lids (like Pyrex shallow baking dishes)
Oven with ‘bread proofing’ setting; or another way of maintaining temperature of 100ºF for 24 hours (the traditional Japanese way is using a warmer called Kotatsu). See more ideas in Notes below.

Instructions
Wash the soybeans and soak for 9 hours in the summer to 12 hours in the winter (I used Instant Pot insert bowl for soaking to wash less dishes).
Drain soybeans in a medium colander.
Place the beans back into the pressure cooker bowl, and add filtered water to cover the beans by an inch.
Use the ‘bean’ setting on Instant Pot, or cook on high pressure for 30 minutes. Let the pressure release naturally when done.
Discard any extra liquid, if any, using a sieve, and place the soybeans back into the bowl of the pressure cooker.
Dissolve 1 special spoonful of Nattomoto powder in 1 tablespoon of sterilized water.
Pour the Nattomoto solution over the beans, and stir them carefully with a spoon.
Divide the soybean mixture between the containers, cover with sterilized cheese cloth,  and cover the containers with lids. I didn’t snap the lids to be air-tight.
Place the containers into a preheated oven maintaining the temperature around 100º-104ºF (38º-40ºC). Let the natto ferment for 22-24 hours.
Remove the natto from oven, and transfer to refrigerator for a night to mature. The next morning, the natto is ready.
Keep it in refrigerator for several months.

Notes
Try to make sure all your equipment is as clean as possible, keep a teapot of boiling water on hand for rinsing.
Cultures for Health recommends covering soybeans with cheese cloth but I didn’t do it the second time, and didn’t notice any difference.
It is perfectly normal to see soft whitish fuzz on the beans after fermentation.
Dr. Mercola recommends using a cold oven with lights turned on; that might work on if you have an older oven, but newer ones have lights that turn off automatically.
If you cut the recipe in half, you could probably fit natto into a yogurt maker like this, it has perfect temperature for natto; just find a round dish to fit inside.
Natto may develop ammonia smell if it’s overfermented.
Homemade natto tastes better and has milder smell than store-bought because of better controlled temperature conditions.
The characteristic smell gets stronger with longer storage.

Print Recipe

5 from 1 vote

How to Make Natto, Japanese Superfood

Homemade Natto, traditional Japanese food, is full of nutrients to keep arteries clean, lower blood pressure, improve digestion & strengthen immune system.

Prep Time15 minutes mins

Cook Time30 minutes mins

Total Time45 minutes mins

Cuisine: Japanese

Author: Valeria - Beets 'n Bones blog

Ingredients

• 2 lbs dried organic soybeans
• Filtered water for cooking soybeans
• 1 tablespoon sterilized water boiled for 5-10 mins, then cooled
• 0.1 g Nattomoto powdered culture 1 special spoon that comes in a box

Instructions

• Wash the soybeans and soak for 9 hours in the summer to 12 hours in the winter (I used Instant Pot insert bowl for soaking to wash less dishes).
• Drain soybeans in a medium colander.
• Place the beans back into the pressure cooker bowl, and add filtered water to cover the beans by an inch.
• Use the 'bean' setting on Instant Pot, or cook on high pressure for 30 minutes. Let the pressure release naturally when done.
• Discard any extra liquid, if any, using a sieve, and place the soybeans back into the bowl of the pressure cooker.
• Dissolve 1 special spoonful of Nattomoto powder in 1 tablespoon of sterilized water.
• Pour the Nattomoto solution over the beans, and stir them carefully with a spoon.
• Divide the soybean mixture between the containers, cover with sterilized cheese cloth, and cover the containers with lids (I didn't snap my lids, so the beans were not air-tight).
• Place the containers into a preheated oven maintaining the temperature around 100º-104ºF (38º-40ºC). Let the natto ferment for 22-24 hours.
• Remove the natto from oven, and transfer to refrigerator for a night. The next morning, the natto is ready.

Notes

• Try to make sure all your equipment is as clean as possible, keep a teapot of boiling water on hand for rinsing.
• Cultures for Health recommends covering soybeans with cheese cloth but I didn't do it the second time, and didn't notice any difference.
• Dr. Mercola recommends using a cold oven with lights turned on; that might work on if you have an older oven, but newer ones have lights that turn off automatically.
• If you cut the recipe in half, you could probably fit natto into a yogurt maker like this, it has a perfect temperature for natto, just find a round dish to fit inside.