homemade natto

How to Make Natto

Natto is a traditional health food in Japan made from fermented soybeans. Highly nutritious and rich in protein, natto is a popular breakfast dish. Natto can be an acquired taste because of its slippery texture (similar to cooked okra) with a pungent smell.

Commonly served over steamed rice with a few drops of soy sauce, natto can also be used to make various cuisines such as natto spaghetti, natto rolls (sushi), natto fried rice, natto pizza, etc.

Before you pour the natto over rice, stir it well with chopsticks or a fork until it gets very sticky for at least 30 seconds. Some people like to add karashi mustard as well.

Yield: Makes approximately 150 g.
Timing: 12 hours to soak the beans, 7-8 hours in a covered pot in Proofer on Slow Cook mode, 18-24 hours on Proofer mode.


Table header 0U.S. Volume
U.S. Weight
Dried whole organic soybeans½ C3 oz
Natto starter (measuring spoon included)--
Ingredients of Natto, dried soy beans and natto starter

Equipment: Brød & Taylor Folding Proofer, 1 large bowl, 4 – 8 quart covered stock pot, and six 1-cup heat-resistant glass containers.

Soak the Soybeans. Place the rinsed soybeans into the stock pot, and cover with enough water to submerge all of the beans. We use about 1 part soybeans to 3 parts water. Soak the beans overnight for 12 hours. The beans will triple in size.

Cook the beans in the Proofer on Slow Cook mode. Place the soybeans in the covered stock pot in the center of the Proofer directly on the aluminum base plate (remove the rack and water tray). Close the lid to the Proofer. Cook at 195 °F / 90 °C for 7-8 hours, or until the beans are soft enough to easily break with your fingers. Drain and place the cooked beans in a large sterilized bowl.

Prepare the natto solution.
Dissolve one special measuring spoonful of natto starter in 2 teaspoons / 10 ml of pre-boiled or sterilized and then cooled water.

Add the natto solution to the cooked soybeans. Pour the natto solution over the warm beans and stir them carefully with a sterilized stainless steel spoon. Note: Make sure the beans are still warm.

Cultured soybeans in glass containers placed in the proofer

Spoon the natto into glass containers. Place a thin layer of soybeans in each of the 5 to 6 sterilized glass containers and loosely put lids over each container. Do not tightly seal the containers.

Culture the soybeans on Proofer mode at 100 °F / 38 °C for 18-24 hours. Place the glass containers on the wire rack in the Proofer. When the natto is completely done, it should show some white filaments. (Do not use water tray in Proofer.)

comparison before and after fermentation

Stop the fermentation. Remove the glass containers from the Proofer. Store the covered containers in the refrigerator at least overnight before eating. The natto can also be aged in the refrigerator for 3-4 days.
Note: Natto with a strong ammonia smell should be discarded.


  • Make sure that all pots, bowls, containers, and utensils that are used while making natto are sterilized.
  • Be sure to only place a thin layer of soybeans in the container when culturing.
  • Leave finished natto in the refrigerator for at least 12 hours before eating.
  • Aged natto can be stored in the freezer and thawed for later use.
Natto served on a bowl of steamed sushi rice

Frequently Asked Questions

What is natto?

Natto is a traditional health food in Japan made from fermented soybeans. Highly nutritious and rich in protein, natto is a popular breakfast dish.

Where can I buy natto starter?

Natto starter culture can be purchased at traditional Japanese and international food stores. It can also be purchase online. Cultures for Health.

What kinds of containers can I use?

Either plastic or glass containers will work. For each batch of natto it is best to use the same sizes and type of containers so that each container will complete fermenting at the same time.

How long does it take to make natto?

It can take up to 2 days. However, most is inactive time. 12 hours to soak the beans, 7-8 hours in a covered pot in the Folding Proofer on Slow Cook mode, and then 18-24 hours with the Proofer set on Proofer mode.

How will I know when the natto is finished culturing?

With a clean utensil and clean hands, look for very small white gelatinous filaments forming across the surface of the beans. Stir a small section of the the fermented beans. You will see filament strands if it is done. Remove from the Proofer, cool and refrigerate.

How should I store natto?

Natto can be stored for several months in the freezer. Place a piece of parchment directly on top of the beans and then seal with an air tight lid before refrigerating.1-3 days of aging in the refrigerator will result in an improved flavor. After 3 days the flavor will become stronger. Natto can also be frozen but is best if eaten within 5 days after it is thawed.

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