Natto Making FAQ

Here are the various Q & A threads from the previous site.
My apology for not getting every threads back in the site.

29 thoughts on “Natto Making FAQ

  1. Thank you, Natto King, for this website and for instructions on how to make it. My first attempt used organic non GMO soybeans. I tried making it in my slow cooker set on ‘Warm’ with a towel over the lid to keep it dark. In the morning I was worried I’d killed the culture because the temperature was over 140 degrees F. But I decided to let it work some more and in another 12 hours (total about 36) I had a fantastic batch of very stringy, stinky natto! We finished that 3 liters already so I decided to try making my next batch using black beans. (I don’t usually eat any soy products because soy is a goitrogen and I have thyroid disease.) I used the slow cooker again but did not leave it on overnight. I just got it up to about 120 degrees and then wrapped it in a goose down cozy to keep the heat in, then during the day I would turn it on periodically to increase the heat. Again, fantastic results. SO stinky and sticky. I don’t eat any grains so my typical meal for natto is bacon and eggs, natto, nori and grilled tomato. I wrap the natto in a piece of dried seaweed with some scrambled eggs. Yum! Today I added some spicy salsa and sour cream to the black bean natto for a kind of huevos rancheros flavor. We love our natto and we do eat it every day (yes, with fat).

    1. > I have thyroid disease
      I am sorry to hear about it.
      If I were you I’d get rid of all fluoride, including fluoridated water and toothpaste (I’m using baking soda aka sodium bicarbonate and it works wonders, no cavities, no pain. We also filter drinking water using Black Berkey; both has greatly improved my thyroid health).

      Trying Natto next week; starter kit on the way. Thanks again for this great website.

  2. First batch came out, as we say in Texas, “Purdy good”! Double-S (stringy and stinky). I used an oven and a 35-watt incandescent lamp for maintaining the fermentation temp–102F to 112F. The beans were a little dry in spots, so, next time, I’ll add an open dish of hot water at the start to increase the humidity, like I had to do “proofing” sourdough bread, years ago. Tnx for all the help!

    1. Hi Dave,

      Awesome! Thank you for sharing your success story and invative “35-watt incandescent lamp” technique. Best of Luck with continuing Double-S. 🙂

  3. First batch came out, as we say in Texas, “Purdy good”! Double-S (stringy and stinky). I used an oven and a 35-watt incandescent lamp for maintaining the fermentation temp–102F to 112F. The beans were a little dry in spots, so, next time, I’ll add an open dish of hot water at the start to increase the humidity, like I had to do “proofing” sourdough bread, years ago. Tnx for all the help!

    1. What you really want is the PQQ in natto, not so much the nattokinase.
      PQQ is in a league of its own when it comes to health improvements.

  4. It’s a pity you don’t have a donate button! I’d certainly donate to this outstanding blog!
    I guess for now i’ll settle for bookmarking and
    adding your RSS feed to my Google account. I look forward to new updates and will share this
    site with my Facebook group. Talk soon!

  5. I thought I’d purchase a natto/yogurt maker for the convenience of having a way to set the time and temperature. They unfortunately only hold 1 liter maximum-about a quart-and I wouldn’t want to fill it up to the brim, so less than 1 quart. But making the beans ready for the machine is a lot of work for so few beans. Here’s my question: if I make a lot of beans, can I just freeze the ones I do not mix with the natto starter? Then, when ready for more, I would just thaw them out, heat them up, mix with natto starter and put into machine for another batch!
    I’d like your opinion before I attempt this method.

  6. After reading some posts, I saw the idea of a 35 watt light in the oven to keep temperature correct for fermentation.
    Sounds like a great, inexpensive idea!
    What kind of thermometer would I get to monitor the temperature in the oven? I’m not a cook, so I’m deficient in basic kitchen gear information.
    Any generic suggestions?

  7. OK, I found a temperature gauge!

    So, the real question is: can I cook and freeze beans, then defrost them, heat them up, mix with natto starter and make natto?

  8. Hi Natto King,

    I had rinsed my beans and noticed that some of the skins fell off or seemed loose. Should I take all the skins off or leave them on for the entire process.

    Also my beans seem a bit larger than what usually comes in the natto packages. After I steam the beans can I cut them in half? Will that help or hinder the fermentation?


  9. Hi. From your first diy natto post, i noticed that you used the fagor pressure cooker. Did you lower the flame on stove after getting the pressure at 15 psi or did you leave it to simmer? Im trying to figure out the best setting for my fagor duo to get the right texture for my soyabean. Also i live in Singapore where e ambient temperature is 32° c. Do i still need to raise the temp to 40℃ by using a hot water bottle?

  10. Am currently fermenting a batch of steamed peanuts and navy, the aroma is as you might imagine, peanuty in addition the natto smell. Can’t wait to try it.

  11. Hello. I live in Ibaraki and have been making natto at home for a couple years now and suddenly the bacteria has stopped working. I’ve changed the bacteria 3 times and still no natto. I’ve changed the beans and still no natto. I use a temperature-controlled yoghurt maker so I know the temperature is okay. Do you know what the problem is? Why after two years of great natto I can no longer make it? I feel like something in the air is killing the bacteria (despite its strength). Any ideas would be welcome. Thanks!

    1. @Mario Leto:
      Can your neighbors make natto?

      You are located about two hours drive from Fukushima:-(

      Your Natto bacteria are being irradiated, as are you and your loved ones. Get out of that place ASAP!!!

    2. One quick fix: change the water you use to hydrate the beans. Your tap water might be contaminated with something that’s killing the natto-moto.

      (I’d still move to another location regardless of the outcome of the above.)

  12. I use a thai rice steamer , for steaming black beans, covered in four layers of folded wet towel, for two to four hours. until firm but easily crushable with fingers. I sanitize fermenting containers and stirring/ scooping utensils using steam, direct flame, or no-rinse sanitizers as used in beer making, like idophor, or better, starsan. After loading beans in fermenting containers (I use stainless steel mixing bowls ignoring the advice I’ve seen to keep the bean layer to 2 inches), stirring once, I let it cool to around 40C after inserting a digital temperature probe in the middle. Then I cover with plastic wrap. I place the bowls in a preheated camping cooler leaving the digital temperature probe to monitor the temperature. To keep the cooler warm I use a night light on an extension cord ( but having two to plug in or our as required might be better) I keep the night light in a glass container to avoid melting the cooler plastic material. I keep it between 35 and 45C for 24 hours stirring once at about twelve hours, and age by refrigerating near 0C for another day. The black beans don’t smell too good after the initial fermentation, but the aging helps. I freeze a couple months supply in 500g containers which I take one by one into the fridge for a few days to a week supply. Doctoring the stirred natto with tamari, fish sauce, dijon mustard, tahini, garlic powder and adding an equal portion of regular beans makes a delectable adjunct to any meal. I’d be interested in any improvements to this method.

    1. @Ken:

      Thanks for sharing.

      > I’d be interested in any improvements to this method.

      > no-rinse sanitizers as used in beer making, like idophor, or better, starsan

      Please read the ingredients list. You don’t want these things anywhere in your home.

      Dodecylbenzenesulfonic acid is toxic to humans.

      “Inert ingredients” 35%??? “Inert” like what? Mercury is supposedly “inert” in an amalgam filling, and it gave me severe Mercury poisoning that took me 20yrs to get rid of. Be smarter than I was. Keep it out of your kitchen and out of your mouth.

      > plastic wrap

      There are no safe plasticizers in commercial-grade plastics (I wasted a lot of precious time researching this topic). Plasticizers are xenoestrogenic hormone distruptors, horribly bad both for men (they ruin testosterone production) and for women (they cause PMS).

  13. Hi Natto king,
    Thx a lot for the sharing! Is there a way to make the Natto kin at home? I prefer making everything from scratch. My sourdough starter was very rewarding after a month of trials and errors!

  14. I’ve been making soy milk and have a ton of okara. I’ve made natto using soy beans (thank you for the info) and am wondering if I steam the okara and inoculate with the natto kin, if I could make natto from the okara.

  15. Great article.

    Just wanted to point out that Bacillus subtilis, also known as hay bacillus, is prevalent in the air, and is abundant on straws. See So, like one Japanese video on youtube showed, you can just add some straws at the bottom instead of natto kin.

    Also, the reason you spray natto bacteria at 80 C is not because it thrives at high heat, but because other germs die at high heat, to prevent contamination.

    Basically, everyone in the U.S. should have an easy access to the making of natto if she has access to soybeans, which the U.S. is the number one producer in the world.

  16. Thank you for sharing your Natto tricks.

    One word of caution, though: **never** use aluminum foil to handle food. Aluminum used to be “safe” (it used to be non-absorbable) but that was before Monsanto gave us Glyphosate, and yes, you and I do have detectable, clinically relevant levels of this toxin in our blood. Glyphosate is a chelator, a really evil one at that, in that it will get Aluminum straight into your brain, where your body can’t get rid of it. This is very serious.

    All the best.

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