how to make nattō in an instant pot

(Due to the popularity of our post on DIY homemade nattō, there have been requests for us to share detailed instructions on how we make nattō in our Instant Pot.)

Instant Pot Nattō

Healthy, homemade nattō, made using an Instant Pot.
Prep Time14 hrs
Cook Time1 d
Total Time1 d 14 hrs
Course: Side Dish
Cuisine: Japanese
Keyword: ferment, instant pot, natto, soybeans
Servings: 12
Author: Holly White - athomeinpuertorico.com

Ingredients

Cookware

Instructions

Preparation

  • Rinse and drain two cups of soybeans and place in a large mixing bowl.    
  • Fill the bowl with water, covering the beans by about an inch (3 parts water : 1 part beans).
  • Cover with a clean cloth or dish towel to keep out dust and soak overnight (approximately 12 to 18 hours).
  • Drain the beans and rinse with fresh water, removing any broken or bad beans.

Steaming

  • Transfer the beans from the steamer basket into the Instant Pot stainless pot and add enough water to completely cover the beans (about 1 inch above the beans).
  • Set the pressure vent to “seal” and cook the beans on “Manual” for 20 minutes. Allow the pressure to come down naturally for 10 minutes.

Sterilization

  • While the soy beans cook, bring a few cups of water to boil in a small pot or tea kettle.  You'll use this water to sterilize your tools.
  • Lay out anything that will come in contact with the beans on a cooling rack over the sink (large mixing bowl, mixing spoon, thermometer, small glass dish, etc.). 
  • Slowly pour boiling water over everything to quickly sterilize.
    Note: Keep about two teaspoons of hot sterilizing water to activate the nattō cultures in the next step.

Preparing the Beans

  • After 10 min. of natural pressure release, open the pressure release valve on the Instant Pot. (I recommend covering it with a cloth to keep the hot water from splashing). 
  • Using your sterile mixing spoon, remove one soybean to test for doneness.  It should be soft in the center and able to be smashed between your fingers with gentle pressure. If it's too mushy, the beans are overdone and will not be usable for nattō.
  • Place the stainless IP steamer basket into the sink or over a large pot.  Remove the beans from the IP and drain into the IP steamer basket.  Then pour the beans back into your large mixing bowl.
  • Place the steamer basket back into the Instant Pot.

Innoculation

  • Using the spoon that comes with the spores, add one spoonful of the nattō spores to the small glass dish.  Add about two teaspoons of remaining hot sterilizing water to the natto spores and mix with a sterile spoon.
  • Add the nattō starter culture mixture to the beans and stir gently but thoroughly to evenly distribute the natto culture. 
  • Dump the beans back into the steamer basket inside the Instant Pot.

Fermentation

  • Cover the pot with sterilized cheesecloth (or dishtowel) and then cover the pot with the glass IP lid. This will keep the beans moist, but prevent condensation from dropping on the beans.
  • Set the Instant Pot to the yogurt setting ("YOGT") for 24 hours. The temperature should remain between 90 and 104 F (30 - 40 C). Even though the Instant Pot does a good job of maintaining the temperature, I like to keep the thermometer in the pot and check it every so often.
  • The beans may take anywhere from 22-24 hours to ferment. When they are complete, you will see a fine white "fuzz" and stringy strands covering the beans. To test, you can gently stir a small area of beans. If gooey strands form easily, the natto is finished.
  • Natto has a distinct, pungent smell. What you don't want is a strong ammonia odor.  This means the beans have been over fermented and won't taste good.

Aging

  • Once the cycle is finished, let the beans cool for about an hour, then place the beans in the refrigerator to “age” for one to three days. This will slow down fermentation and enhance the flavor.
    diy homemade natto
  • To prepare the natto, add the desired amount of natto to a rice or cereal bowl and mix vigorously with a spoon or chopsticks.  Add soy sauce and finely chopped green onions to taste.  Serve over hot rice, warm mochi, or simply topped with diced toasted nori for a Paleo version.

Notes

We usually put the nattō in two separate containers before aging so that once complete, we can keep one in the fridge to eat within the week and then store the other in the freezer for later.
Also, if you notice your nattō is not very sticky, you may need to get a fresh batch of spores.  Good luck and enjoy!
how to make nattō in an instant pot

As you read and try out our recipe please keep in mind this is a work in progress.  We are still experimenting and trying new tweaks.  Please share your findings in the comments below to help us all in the never ending quest to make that perfect batch of delicious homemade nattō!

13 comments


  • testing review feature…

  • AWesome! Thank you.

  • Excellent, this was my first attempt at making natto and it worked! I mixed these instructions with others that I found online and I now have a nice batch of natto aging in my fridge. I used store bought natto instead of natto spores. It was a tedious process but worth it!

    • Yes, the process can be a bit of work, Tina, but I agree with you…totally worth it! Congrats on your success! Glad you were able to “make it your own.” 🙂

  • Thank you for this and I will definitely try your recipe. One question- How do you sterilize a cheese cloth?

    • Hi Ume! You can sterilize the cheese cloth by simply pouring boiling water over it as in step 3 of the Sterilization step. Honestly, I have a hard time finding cheesecloth here in Puerto Rico, so I usually just use a few layers of dry paper towels instead. That may not be technically correct, but I’ve never had a problem and it works great. 😉

  • I think I posted my question with a wrong email address so trying again – how do you sterlize a cheese cloth?

  • I don’t have a steamer insert and have been making the natto directly in the ss liner, works just fine too. After cooking the soybeans I drain, cool a bit, return to pot, and add starter, cover top with a paper towel then lid, and set on yogurt for 24 hours. I also learned in Korea they make something similar called Cheonggukjang using wild bacillis without the need to buy starter, but fermented almost twice as long, then ground into a paste. Curious to try it someday, sounds like it could make a great non dairy cheese like spread.

    • That’s great, veggietater! I’m glad the stainless insert alone worked for you; I’ll have to give it a try. When I first started making natto (in my pre-IP days), I had read that the beans needed to be quite shallow in the fermenting vessel to allow for maximum exposure to the starter culture (only 3 beans deep). However, with the IP, you run into an issue of space….the steamer basket was my answer to that limitation. Cheonggukjang does look interesting! I wonder if I inadvertently made it once when I had “over-fermented” my natto beans. The aroma and texture sound just like what I got…if only I had known, it was still edible! ;D

  • Where to you get the starter for the natto

    • Cultures for Health sells spores. You can buy natto and use as a starter if you have an Asian Grocery nearby. Amazon also sells spores.

  • Diane Brincaccio

    One question: When you return the cooked, inoculated beans back to the Instant Pot, do you need to have water below the steamer for the 24-hour “yogurt” setting?

  • Can you make a video?

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