Umami Mart Registry

Natto is the one of those foods that elicits strong reactions. I get overwhelmed with a sense of joy and excitement, but the response I hear from most people (who aren't from or aren't descendants of the eastern regions of Japan) is pure disgust.

I remember how clueless I was junior year in college when I stocked up on natto and brought it back to my fridge that I shared with four other UC Santa Cruzers. As I was innocently devouring a package of natto, my roommate barged in yelling "Oh my god! What is that smell?!" My answer to her was, "Are you talking about your pet rat?" as I gestured my chopsticks (all stringy with natto strands) to point at the corner of the room where her pet rat resided. She shook her head and inched in closer to me to inspect the contents of my bowl.

It never registered to me that cold food could smell -- and up until that point, I never suspected that natto even had a smell.

That was my first lesson in how natto could offend people. From that day forward, I could not eat natto so long as I lived with roommates.

Natto is fermented soybeans that were traditionally made in kotatsus in Japanese homes in the Kanto (Tokyo) region. It's like yogurt in the way that you start with a culture. In the case of natto, the culture used is bacillus subtilis and the medium is soybeans which are left in a humid, warm environment for 24 hours. The result is a mixture of stringy, luscious soybeans that are kind of like a soft cheese in texture with an aroma like no other. Some describe it like smelly French cheese... while my roommates told me it smelled like feet.

Natto is getting some attention because of its health benefits. Eastern regions of Japan have less incidence of osteoporosis. Plus, that sticky stuff apparently contains some enzymes that thin the blood, therefore, preventing heart attacks, strokes and certain types of cancers. I guess they even sell natto in pill form and call it "Nattokinase" here in the west.

My love for natto was evident from my early days -- soon after I exited the womb. But our bond strengthened exponentially when I moved to Tokyo where I could indulge in my love for it with no shame or judgment from my peers. Plus they were regularly priced at a dirt-cheap 30-cents a serving. I would eat a package every morning before dashing off to work. It was like my daily cup of coffee.

So when I came back to the U.S. last month, I braced myself for an environment that would challenge my love affair with natto. It's not that expensive here in California at about $2.00 for three servings, but that's still about twice the amount I was used to in Tokyo. Plus, it's not readily available, say at the local 7-11 or Safeway.

I concluded that the only way I could rely on a steady and affordable supply of natto was to make it myself. My experience with making yogurt for four years, gave me the confidence to try my hand at natto as well.

Here's how I made it:

1) Gather together the following ingredients and supplies: 1 lb of soybeans, a store bought pack of natto, water, glass containers, foil


2) Soak soybeans overnight in plenty of water.


After one night:


3) Drain the soybeans.


4) Steam the soybeans until you can smush them between your thumb and pointer finger.


I used my rice cooker which also can act as a pressure cooker. I ended up steaming the soybeans for 40 minutes.


5) While the soybeans are steaming, sterilize the glass containers you will use to ferment the soybeans in. I set my oven to 250 degrees and placed my glass containers in there for about 30 minutes.


6) Break out the store-bought package of natto.



7) Once the soybeans are done steaming, combine them with the store-bought package of natto.



8) Mix well then place the beans into the sterilized jars. Cover the jars with aluminum foil. Poke holes in the foil so that the soybeans can "breathe" during the fermentation process.



9) Okay, the beans are now ready to ferment. The basic idea for creating an ideal environment is to keep the beans in a humid, warm climate at about 40 degrees celsius (think mid-August Tokyo in a small room on the fourth floor with no windows and air conditioning). So I decided to keep the jars in my Crock-pot filled with a little bit of water on the "warm" setting. People also seem to use ice boxes filled with hot water bottles.


10) Wait for 24 hours.

The suspense got the best of me and I took a peek inside after 12 hours:


And the next morning they really seemed all mature and grown up.


Look at the stringiness!!! I was a very proud parent.


11) But the wait was not over. These beads of joy must be aged for umami in air-tight containers for a few days to one week in the refrigerator.

12) I finally got to indulge today over rice and I experienced a deep sense of pride and accomplishment. With a dash of soy sauce and Japanese mustard mixed into my home-made natto, I knew I had achieved nirvana for my taste buds and wallet.



13) To complete the cycle, freeze a portion of the natto to use as the starter for the next batch of natto.
Column: Japanify


  • Thank you for the Wonderful Detailed Instructions on how to make Natto! I ran into problem trying to figure out how to Incubate my Natto for 24 hours? So, I didn’t want to buy a crockpot to Incubate my Natto? Well, i found a Beautiful Stainless Steel deep pan with lid and an opening, which I decided to use as Incubator? It is perfect and i set my electric stove at Low and i will be watching it for 24 hours. Thank you again. 🌺

    Betty FAgan on

  • This is life-changing!!! Family favorite that ends up taking a lot of my money, and now I can make as much as I want for meals! Thank you so much!

    Arisa on

  • Have you tried just putting the beans straight in the crockpot on warm? If so how did that go?

    Guillaume Williams on

  • Excellent presentation and very useful information. To hold a stable fermenting environment, I bought a temperature controller used by home beer brewers (about US$15) & use a 60 watt incandescent lamp, shielded by a tin can with both ends cut out to form a chimney around the lamp, inside a cooler chest. Set the temperature controller for 98 – 100 F. There’s an extra pan of water in the chest to keep the humidity up. If anyone cares,, I’d be happy to send photos.

    Andrew Lyke on

  • where can I buy the natto fresh to use for culturing?

    Gay Richardson on

  • Excellent. After several different ways I started doing similar to yours. I made it simpler, I think. After steaming I do put in a ice chest but I place a heating pad in low temp. Leave them for 48 hours. That’s the way I am doing now. Willing to try more different ways to improve. Also, I steam 60 minutes. Used to do 40 minutes. Enjoy Natto! And stay healthy!!

    Toshimasa Wada on

  • The best description of a doable way to make natto. Thank you, Yoko. Began to use the store bought version $3.99 per in Hawai’i where currently live. Hope to check back and write my results, eventually. Natto is unique, very special, and want to have more than the 1 teaspoon I read contains all the K2 one would need daily. Amounts of K2 are measured in mcg: Natto contains a huge amount – way more than any other source. It also seems to change one’s sensibility – or whatever – meaning that all foods do affect how one feels. Even a very small amount of natto seems to have a positive effect; it’s very subtle.

    Nandarani on

  • For those who use the Instant Pot to pressure steam the soybeans, how long do you pressure steam them?

    Sergio Valadez on

  • oh this might be the BEST post so far. Good job Yoke!

    tomo on

  • Super cool work, Yoko. Otsukaresama.
    …but still disGUSTing!

    Anders on

  • Thanks! It was really fun to do and write about. I can’t wait to make my next batch.

    yoko on

  • i should tell my mom. she constantly buys the $2 packets lol.

    wen on

  • Amaza-craza-cryin-crazy-amaza-cryin-crazy.

    kayoko on

  • Yoko-chan,

    Sugoi! That is such a nice write-up. I cannot wait to try making my own. When I go to Japan, I order Mito Natto made in Ibaraki. It is so good compared to the store bought one.


    keji on

  • Mmmm! Eating Natto with hot sauce sounds SO good! I should try it. Yeah, aging it for a week is kind of torturous… but worth the wait.

    yoko on

  • This is the best way yet! Thank you so much!BTW, my favorite way to eat is with hot sauce and greens. hmmmmmmmm

    Still, I dont know if I have the patience to wait for one week after all the work.

    Laurin on

  • tell us more about Ibaraki natto. what makes it so good?

    Kayoko on

  • Keji, Thank you so much for reading my post! Please tell me how your natto-making goes. Mmm ibaraki natto is the best.

    yoko on

  • I am not Japanese or even close, but I love Asian food. I tried natto because of the heart-healthy reputation and have become quite addicted. It is way better than some other fermented foods like sourkraut or vegemite. Give me natto any day! This tutorial is excellent. I’m going to try to make my own batch.

    caucasion Sandy on

  • Hi Kayoko-chan,

    Ibaraki natto is made the traditional way in Mito City, the capital of Ibaraki prefecture. The prepared beans are fermented in rice straw called wara. The wara has the natural natto bacteria starter. The taste is nothing like the natto that stores sell in the styrofoam packs. If you ever have a chance to try it in Japan, you will be in for a real treat!

    keji on

  • My beans came out sweet, sticky with long strings but did not the strong ammonia smell.
    Also, when they were fermenting, they produced a strong smelling gas that was neither ammonia or sulfur? That you for your website.Susan

    Susan Heinemann on

  • Thankyou for sharing!

    There is only one place I know of in Nova Scotia that sells Natto…and they charge 6.00 for 3 packages!I will try this method!

    Abe on

  • caucasion Sandy
    Wow! You are a rare bunch. That’s great that you are getting into natto. It does have many benefits… Personally I just love the taste. Tell me how your natto-making process goes. Is natto in packaged form pretty accessible where you are?

    yoko on

  • I am not Japanese but love natto. I used to make it myself with an incubator but would like to try the crockpot. Doesn’t it get too hot even on the “warm” setting?

    Adrian on

  • Hello Susan,

    Thanks for visiting my post and trying out this natto recipe! You are truly adventurous. What kind of beans did you use? I ask because it is interesting that they turned out sweet. Natto does have a minor element of sweetness but they don’t taste like red bean paste. The smell of natto will not necessarily be a strong ammonia smell but you will smell a curious aroma. Good luck on your next batch!

    yoko on

  • Hey there! I’ve been eating natto every morning for 2 years. I finally decided that making a trip to the asian market all the time for the expensive frozen packets had to stop, so I started making my own. 6 months now, and I have a pretty good system. I put mine in a gas oven with a light bulb in it for the heat. And I use 9″×9″×2-1/2" baking pans, filled to the rim with the beans. I cover tightly with foil right over the beans and poke lots of tiny holes in the foil. There seems to be plenty of air for the critters, but the beans don’t dry out (especially on the edges). Personally I like the natto soft, so I pressure cook the beans for 45 minutes.

    Dennis on

  • The warm setting is not too hot, as long as you don’t place the lid on tight. You also want to make sure there is enough water around the jars so it’s a gentle steam.

    yoko on

  • Hello Thao,

    Thanks for reading my post! Hmmm, what do you mean by 10 minutes? The natto needs to ferment for 24-48 hours. You need to check it to make sure the strings develop. Another culprit may be that you didn’t add enough “kin” or the store bought natto. How many pounds of steamed natto did you use? It’s cold right now, so you may need to add more of the starter natto, perhaps 2 packages of store bought natto. Let me know if this helps.


    Yoko on

  • Hello Yoko,
    Thank you very much for your wonderful web site,very clear direction. I made my batch last 2 weeks.It come out with some thin white film on the surface of beans but no stringiness at all and smell very strong. I don’t know what was wrong. Maybe teperature was too high 190 about 10 minites when I walk away didn’t see to turn off the oven or the soy beans were litte bit hard and dry??? Now it’s less smell strong and the taste not bitter. I don’t know it’s OK to eat. Please help!!!!!!!!

    Thao on

  • Dennis,

    Yes, a good pressure cook for the beans is necessary for the right texture. That’s great that you are making your own natto! Power to you!

    yoko on

  • I tried to make natto by steaming the soy beans using a pressure cooker for 25 minutes and then added a half pack of store bought natto and mixing well then kept in the oven for 24 hours at(104F). Every time I try the natto it smells like ammonia. I am not sure if it is safe to eat so I have been throwing it away. Can you tell me if there is any way to eliminate the ammonia oder? I poured boiling hot water on everything I use to make natto before I start to kill any germs. Please help! Keiko

    Keiko Brown on

  • Sorry for my unclear writting. I mean I kept temperature around 104 F like you said but afer 6 hrs I turned the oven back on ( becau se it went down to 76F ) about 10 minutes later when I remember to turned off it went up to 190 F !!!! I quickly turned off , opened the door took the beans outside wait for oven to cool down and put it back.
    After 24 hrs the beans had some strings and smell little bit like natto and soy beans. I though maybe not done yet so I let it sit for 24 hrs more in room temp (72 F day time, 61 F night time).The next day the white film were still but the strings were all gone, why??? I used 2 lbs bean and 2 packges store bought natto. I will try again next time like you said. Thanks for your help.

    Thao on

  • Great post!!! I’m trying the crock pot method today. :)

    Jenell on

  • Can you make natto with navy beans?

    Tom on

  • Thanks for reading Kath. I have a Sanyo which works great for me. But I know what Zojirushi cookers are great too. Just make sure you don’t get one that is too small in capacity as you will have to be able to steam a good amount of beans for this recipe.

    yoko on

  • Hi. Great post. My current rice cooker does not have a steaming option so I am in the market for a new one. Do you have some recommendations?

    Kath on

  • Very nice photos! Fermented foods have been of my interest lately and natto was very hard to find. I found some recipes in but this was indeed very helpful. Thanks!

    doreen on

  • bbgg. Wow, that sounds really good. I will try it next time.

    yoko on

  • The way I enjoy natto best is to mix it with a dish of “Spaghetti aglio e olio” (spaghetti, garlic, chili, olive oil). Now I am addicted!

    bbgg on

  • Thanks for the great instruction page!
    I am interested in trying to make this! I just read about the specific health angle eating this can offer involving vitamin K2. Without K2 as a regular part of the diet Calcium can end up killing you because K2 is needed to direct it into the bones. (it is actually more complicated than this involving vitamin D and E too but….) Suffice it to say that otherwise too much gets stuck to your blood vessels! Natto provides what would have to come from dairy or meat or eggs and none of these have vitamin K2 anymore unless the diet of the producing animals are truly pasture raised!! Good luck finding pasture raised anythig anymore at a reasonable cost.

    Abe Liever on

  • Can you please tell me if it is possible to make natto with any other beans then soy?

    eva on

  • I just finished today a batch of chickpea-natto. The smell in the container under the plastic wrap was like ammonia. At the moment it’s outside to get rid of it, afterwards I put it in the fride.
    When I tasted it, it’s like heaven, the smell disapears and it’s nice and slimy :)
    Actually, I seem to like chickpea natto better than the soybean natto.
    Though, the chickpeas didn’t get the wrinkles as the soybeans did even though I had them more than 50 hours in the oven at the recommended 40° Celsius. The slime looks normal.

    My first batch was soybean natto, but that didn’t had this strong ammonia smell. After 30h it was really wrinkly and had lots of the slimy stuff.

    I only use like a small portion of a packaged natto, like 20 beans (over here the cheapest 3 portion package costs almost 6$).
    I put it in 1dl of luke warm boiled water and added 1 tablespoon sugar and a little salt (as I do to make yeast grow to bake bread) then I poured it over the cooked beans and stired them.
    That seems to produce lots and lots of the slimy stuff :-)

    susanne on

  • Thank you so much for a great recipe. I was always afraid to try to make it myself but it was a snap following your directions. I used an oven with a 60 watt bulb and a tray of water for the incubation period and it turned out super. Now I can eat as much as I have always wanted but could not afford.

    Robert Mueller on

  • I am so excited to try making my own natto. My Japanese mother would have been so proud. Domo aarigato gozaimashita.

    Marrietta on

  • Way too much work to make it. It’s so cheap to buy it in Canada. It’s only 1.99$ on sale for a pack of 4 styryfoam.
    I add condiments and green onions among other crunchy things like croutons with my natto in the morning.
    I wrote an article on my natto experience here. Check it out.

    hogtownmark on

  • I’m in hour 12 or so of making my natto. I tried this method with the natto spores and I’m concerned that I may have killed off the spores before I even put my jars in the crock pot to keep warm. I’m also hoping that my warm setting didn’t kill off all of my culture by being too warm. Does this method only work with the package natto as a starter? Will the packaged natto still work if it was frozen? Thank you for your awesome blog!

    Cindy on

  • Do I need just one styrofoam pack of natto? Or all three packs? Thanks in advance!

    Betsy on

  • I’m starting to make natto, I saw a posting by using google. It involves steaming by pressure cooker, then using a machine available only in Japan(100V), brand is Yogurtia by Tanica Ym-1200. it’s available in Amazon but pricey upward of $110. I’ll try yours since i’ve already the pressure cooker & crockpot. I think its more economical to use as starter the fermentation package than the natto .

    Taneo-San on

  • If you don’t like the ammonia smell/taste, (yes, it should smell or taste a little bit like ammonia – like a strong brie mould!), then prepare your natto by mixing with a little vinegar befare adding to anything else. Vinegar neutralizes the pungency and makes it more palatable if you don’t like it. My Japanese friends use rige wine vinegar, but if you mix it in Italian food, for instance, you use balsamic – whatever vinegar is appropriate to the cuisine.

    gloria on

  • Betsy, just use one styrofoam pack!

    YOKO on

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