How to Make Natto

Co-authored by wikiHow Staff

Last Updated: August 10, 2022

Natto is a traditional Japanese dish made from fermented soybeans that's known for its pungent smell and strong flavor. It's often served with rice and mixed with egg as a breakfast dish, though it's sometimes topped with soy sauce and Japanese mustard for a mid-day meal. While you can buy pre-made natto in many parts of the world, making it fresh usually provides the best flavor. Making natto is a time-consuming process, though the hands-on time only amounts to about an hour so you just need a little patience to enjoy this Japanese delicacy.

Ingredients

4 cups (800 g) soybeans
Water, for soaking
2 teaspoons (10 ml) water, boiled
1 spoonful Nattomoto powder

Part 1

Part 1 of 4:

Soaking the Beans

1
Wash the soybeans. For the natto, you’ll need 4 cups (800 g) of soybeans. Place the beans in a colander or strainer, and rinse them thoroughly under cold water in the sink. Shake the beans well afterward to remove the excess moisture.^{[1]
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- As you rinse the soybeans, remove any shrunken or discolored beans.
2
Soak the beans overnight. After you’ve rinsed the soybeans, place them in a large pot. Cover the beans with 12 cups (2.8 l) of cold water to create a ratio of 3 parts water to 1 part beans so the beans have room to expand. Allow the beans to soak for 9 to 12 hours.^{[2]
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- During colder months, you may need to soak the beans longer, so it may take as many as 15 to 20 hours.
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3
Drain the beans. When the beans have finished soaking, dump them into a colander or strainer. Shake well to remove all of the excess moisture.^{[3]
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Part 2

Part 2 of 4:

Cooking the Beans

1
Transfer the beans to a large pot. Once the beans are drained, place them in a large pot. Use a stainless steel, enameled, or other non-reactive pot because reactive materials may alter the taste and color of the natto.^{[4]
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2
Cover the beans with water and cook them until they’re soft. Pour enough water into the pot to completely cover the beans. Place the pot on the stove, and bring it to a boil over high heat. Once it’s boiling, turn the heat down to medium and allow the beans to simmer for 9 hours.^{[5]
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3
Strain the beans. When the soybeans are finished cooking, place a colander or strainer in the sink. Pour the beans into the colander and shake well to remove all of the excess water.^{[6]
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Part 3

Part 3 of 4:

Combining the Beans and Nattomoto Powder

1
Place the beans in a sterilized pot. From this point in the natto-making process, it’s crucial that all of the containers and utensils you use are sterilized or mold and bacteria may develop. Boil a pot in water on high heat for 10 minutes to sterilize it. Dry it with a clean towel, and then add the beans to it.^{[7]
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- Boil any spoons or other utensils that you’ll be using to mix as well.
2
Combine the nattomoto powder and water. To make the natto, you’ll need nattomoto powder, which contains natto spores. Use the special spoon that comes with the powder to add one spoonful of the spores to a small sterilized bowl. Add 2 teaspoons (10 ml) of boiled water to the powder, and stir the mixture with a sterilized spoon until the powder dissolves.^{[8]
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- Nattomoto powder is also known as natto spores or natto starter. You can purchase it from Japanese grocery stores and online retailers.
3
Pour the natto spore solution over the beans. Once the nattomoto powder has dissolved, cover the beans with the solution. Use a sterilized spoon to stir the beans and solution together so they’re fully combined.^{[9]
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Part 4

Part 4 of 4:

Finishing the Natto

1
Preheat the oven. To finish the natto, you’ll need to warm the beans in the oven for several hours. Set the temperature to 200°F (93°C) and allow it to preheat fully.^{[10]
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- If your oven temperature doesn’t go as low as 200°F (93°C), use the lowest heat setting possible. You can even go as low as 100°F (38°C) if possible.
2
Add the beans to oven-safe jars. Use a sterilized spoon to add a thin layer of beans to the bottom of 3 to 4 oven-safe glass jar. If any of the beans fall onto the counter or table during the transfer, discard them.^{[11]
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- Make sure that the jars you use have lids.
- Sterilize the jars in boiling water before filling them.
3
Cover the jars with cheesecloth and the lids. When the beans are in the jars, place a piece of sterilized cheesecloth over each one. Next, place the lids on the jars, closing them tightly.^{[12]
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4
Place in the oven to ferment for 24 hours. Once they’re closed, place the covered jars in the preheated oven. Allow the beans to ferment in the oven for 22 to 24 hours.^{[13]
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- You can also place the jars in a food dehydrator to ferment the beans.
5
Allow the natto to cool. When the beans are finished fermenting, remove the jars from the oven. Let them cool for at least two hours.^{[14]
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6
Remove the cheesecloth and recover the jars with lids. Once the beans are cooled, remove the lids from the jars and discard the cheesecloth. Replace the lids on the jars so they’re tightly closed once more.^{[15]
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7
Refrigerate the natto overnight. When the jars are recovered, place them in the refrigerator. Let them chill at least overnight or up to 3 to 4 days.^{[16]
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- Natto are often served as part of a Japanese breakfast. It can also be incorporated into your meals in other interesting ways.

Community Q&A

Question

Can I use instant dry yeast instead?

Community Answer

Yes. You'll want to make sure you allow some moisture during the baking process so the product is fluffier and rises accordingly.