Black Bean Natto

black bean 1

Note from Shannon: Please welcome Sarah, CFH Customer Service Representative and Cultured Kitchen-Keeper.

Natto is purported to be one of the most healthful forms of fermented soybeans. But, soybeans are not the only legumes you can make natto from.

With just two pounds of rinsed organic, dry black beans ready for an overnight soaking, you too can get started making your own black bean natto. Here’s how.

In the morning, rinse your beans well and place them in a large pot with fresh water. Bring to a boil and cook the beans until just tender. I prefer my natto with some firmness, but if you like really soft natto, keep cooking longer. I boiled mine for about 30-40 minutes, until they were the tenderness I wanted.

While these are cooking, start another large pot of water. Bring to a boil and start adding any utensils, measuring cups or containers you will use to make your natto. If it’s going to touch the beans, boil it.

Drain the cooked beans and place in your large, boiled bowl. Stir the beans occasionally to make sure they cool evenly. You want to bring them down to 110-115° temperature range. Mix one scoop of the natto spores into 2-3 Tbsp of freshly boiled water that has also cooled. Pour over the beans and stir well to make sure the culture is evenly distributed. If your beans are particularly dry, add enough more boiled water to moisten. This is not a dry culture like Tempeh.

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Yes that teeny little scoop is all the nattomoto you need to make a big batch of natto!

Now transfer your beans to shallow pans that will fit in your culturing appliance of choice. If you are using your oven, go big!. I used my small cooler, so I found some small containers that would hold my beans at a depth of 2-3 inches.

To cover your beans, either boil cheesecloth or muslin and wring out, or use unbleached parchment paper. Lay the cloth or paper over the beans, and then seal the container with a layer of foil. Place the beans in your culturing place that you have confirmed maintains a temperature of about 100°F.

A cube dehydrator works very well. Some people have an oven with a light that will maintain the correct temperature. I use a small cooler and heating pad.

A trick I have learned for making natto with lots of strings is to “heat shock” the natto. For the first 2-3 hours that your natto cultures, try to keep the temperature near 110°F. Then drop the temperature down to 100 for the remainder of the time. My batch of black bean natto took 23 hours to culture.

An important consideration, especially if you live with others, is to find an isolated place to culture your natto. It has a very strong smell while culturing! And during a 23-24 hour culturing time, you are bound to have complaints! A garage, sheltered spot outdoors or even a room with a good ventilating fan are all good options. Culturing near an open window next to a fan would also work.

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As soon as your natto is forming lots of stringy gels, transfer it immediatedly to the refrigerator. After 6-8 hours, it is ready to eat.

I ate mine for breakfast with some rice noodles in spicy sauce with lettuce, green onions and a poached egg.

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I have had some questions from customers about their natto not being as stringy as commercial natto. So here is a comparison. The first picture of the finished beans is just plain natto after being refrigerated for 8 hours.

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This one is with some tamari stirred in. Just a little liquid makes a big difference! If you are comparing your natto to commercial natto, keep in mind the ingredients and that the commercial natto has been aged for a while before making it to your bowl.

Natto will keep for about 4-6 weeks in the refrigerator, though the smell will intensify as it ages. For a mild flavor, it is best to consume it within a week. For longer storage, you can freeze natto for several months. But you will need to consume it within 5-7 days of defrosting.



I live in Oregon with my 4 kids. I hop between my kitchen and sewing room. As the daughter of a ranch-girl turned County Extension Agent, I really believe that with enough ingenuity and know-how, anything can be made. I try to keep some cultured vegetables and condiments on hand, as well as a robust supply of yogurt. What really excites me though is finding old ways of culturing foods from around the world and making it work in my life. “I wonder” is a phrase I utter a lot, and can make my kids nervous! I love to learn and share what I’ve discovered.

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  1. VICKI says

    Thanks for the pictures and the “how to do natto” information.

    I know it came up in my recent research, but I cannot remember the details of its impact on the gut and how it can be used to heal.

    It appears that I have a BUNCH to learn! :-)


    • Sarah says

      The Vitamin K levels should be fairly similar. However, I’ve not seen a study yet on the results with different beans and cannot answer that definitively.

  2. Dwight says


    • Sarah says

      While vegetables can be cultured with natto, there is a bit of a trick to getting them cooked enough to remove other bacteria and not cooking so much that the vegetables are mushy. All fermentation will result in vitamin K, so I recommend lacto-fermenting vegetables. They are much more pleasant to eat this way!

  3. aa says

    Great write up. I just finished making Natto out of black beans and they came out really well. I sprouted mine, and cooked them until they were very soft. (at least with sprouting you can be sure the beans are vital, unlike some Adzuki beans I tried to sprout – didn’t work – the were sitting in a warm shop too long.) Anyhow, my previous batch were not nearly as soft and no strings resulted. The bacteria have to be able to penetrate the bean easily, so the outer skin must be broken and the inside should melt in your mouth (just my experience.) Another important thing is humidity when fermenting. It needs to be very humid, and there still needs to be airflow.

  4. Brandon says

    Wow, I just discovered Natto and its health benefits, and can’t wait to give making it a try. I try to limit the amount of soy I eat so this recipe is perfect. I have a couple questions maybe you can help me with.

    Do you know if the culture would produce nattokinase when using beans other then soy? and if so would it be at a similar level?

    Also I’m a little confused as to how long the natto will keep once prepared, in this recipe it says 4-6 weeks in the fridge but I read Q&A section under the spores that they are good for no more then a week in the fridge?
    And finally are you just cooking the beans until tender before they are inoculated?

    I’m excited to get started, thanks for providing such an awesome resource.

  5. Thomas says

    Thank you for the great info. I was wondering if it’s possible to use the natto beans as a starter to inoculate other batches of beans.

  6. Dwight says

    just made natto with adzuki beans. noticed that the sticky strands were much shorter and did not know why. I have started shocking my natto for the first 2-3 hours at 110 degrees. I have to turn the oven on every few hours because my heating pad does not keep temp at 100 degrees. I did this once at about 2 hours and forgot to turn it off after 15- 20 seconds. Temp got to 120. Went back to links and found this;

    “Temperature – This is the most critical factor in making Natto and any fermenter will probably agree. During the fermentation cycle, the temperature of Natto should be kept in the range between 38 – 45 C (100-113 degrees F). While many “How To” documents says around 40 (104 F), it is OK to keep it higher. Important is not to get below 38 degrees. However, if you keep it too high (more than 45 C), your Natto will be less sticky.”


    I am noticing that the smell is less intense with adzuki beans.

    Also I am not boiling my utensils – beans are cooked in crock pot – then starting with the large bowl they cool in I wipe any surface that will contact the beans with a clean paper towel after I spay the area with 90% alcohol. I repeat this with the spoon I am using and the glass baking dishes I use for incubation. I do cover the beans while the are cooling in the bowl because I find that most contaminants are floating in the air. I also just use aluminum foil only to cover the glass dishes while in the warm oven.

  7. Jeff says

    Thank you for blogging about this. I just started eating packages of natto from Japan. When I open a package I don’t smell anything offensive. It just smells a little like soy sauce perhaps? Anyway, I don’t like the idea of consuming a lot of soy, so two days ago I decided to try making black bean natto using the culture from a package of soy natto. Immediately after fermenting for 24 hours as well as after 2 days of aging in the refrigerator, it stinks like dirty feet. Is it because I used black beans? So they do something in Japan that tames the odor? Any thoughts?

  8. Adrian says

    Dirty feet sounds about right. When I have the strong odour and plenty of slime I am confident of a successful fermentation. I have nattified green peas, chick peas, black turtle beans and soy beans and I would recommend people start with chick pea until they are used to the natto experience. They are the mildest in odour and taste and will receive the least objections from other family members. Happy nattoing.

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