Tuesday, June 4, 2013

Troubleshooting Guide for Homemade Natto

I have made many bad batches of natto. Hopefully this troubleshooting guide will help homemade natto makers out there make better natto. If you have any questions that are not listed here, please email me at "Contact Me" or directly at my email if you want to attach pics.
Hi all again, I have updated this as of May-2020, so please take a look if you had visited the guide before.

Before going through the Q&A, here are the most basic requirements to make good natto.

1. Fully hydrate soybeans. 16-20 hours for Summer time and 20-24 hours for Winter time.
-Update: Better to soak for longer than for shorter if time allows. So even in the warmer months, soak for 20 hours. For me, I will wash and soak the beans before I go to sleep and then make natto after coming home the next day. 

2. Cook beans by steaming under pressure. This means putting beans in a basket and steaming them in a pressure cooker making sure that most of the beans do not touch the water. The cooked beans should be soft enough to squish with your thumb and pinky and should have the consistency of a thick paste.
-Update: For my pressure cooker, it takes about 40 minutes, but this may vary with your setup.
-Update: The beans should be light beige in color and not yellow after proper cooking time. 
-Update: If the soybeans are hard after fermentation, the beans did not cook for long enough.
-Update: Boiling under pressure (beans immersed in water while cooking) results in wet beans and can cause a waxy low thread natto and/or high ammonia.

3. Use frozen packaged natto as starter. 
-Update: you can also use spore starter and
but make sure to dissolve the spore in 80 celcius water. Using spore starter for me, tends to result in higher failure rates when compared to frozen packaged natto. Refer to the 'Spore Starter Natto' on Youtube for optimized instructions.

4. Update: Ferment beans and hit at least 42C (108F) earlier in the fermentation, with a temp range of 40-42C (104F-108F). Total fermenation time is 18-22 hours. Fermenting longer will not fix any issues or produce more threads.

Q: My natto is not stringy, what's up?

A: This one is the hardest question and probably deserves its own post.

A: Low temperature will result in the natto not growing properly. It is important to reach 42C (108F) during the fermenation. Shoot for 40C - 42C (104F-108F) for 18-22 hours. Natto is okay with temperature fluctuation and will survive heat spikes up to 45C (113F) and maybe even up to 50C (122F) for short amounts of time. 

A: The soybeans were not cooked long enough. The cooked beans should be easily squished with the thumb and pinky and have a creamy texture. Steamed under pressure takes 40 minutes to reach this with soybeans.
Update: If the soybeans are hard after fermentation, the beans were not pressure steamed for long enough.

A: Another possibility noted on some natto blogs is that the fermentation temperature is too high.
-Update: Usually 9 out of 10, the fermentation temp was too low which made the fermentation fail, not because the fermantation was too high. Natto is okay with short heat spikes up to 113F and maybe higher.

A: I used to think that overcooking the soybeans somehow destroyed a nutrient to make the silky threads, but this is not the case. Overcooking should not be a concern from what I have seen. As a note, I have noticed that boiling soybeans will make the natto have a non-stringy rubbery growth on the beans.

Q: My natto looks white and leathery.

A: This is related to the question above. When the natto is not stringy, it usually turns out leathery and white. This might be related to lower fermenting temps. 
-Update: Make sure you are reaching at least 42C (108F) in the fermenation.

A: The soybeans were too wet which can happen if you boil or pressure boil the beans. Pressure steaming is the best way to cook the beans.

Q: My natto stinks of ammonia.

A: I associate this with temperature problems. One of my earlier batches smelled strongly of ammonia and the natto was not stringy. If I remember correctly this was because the temperature was too low and I left the natto batch fermenting for more than 24 hours waiting for the stringyness to appear.

Q: My natto does not have flavor.

A: Boiling the soybeans is the reason why natto turns out flavorless. Boiling them in a regular pot or boiling them under pressure will do this. Curiously the skin of the soybean will come off when boiled. To resolve this, you must cook the soybeans in a steamer basket or strainer above the boiling water so most of the beans do not touch the water. I use a small glass bowl to suspend the steamer basket over the boiling water.

Q: My boiled soybeans are soft, but the natto is hard.

A: The reason is that the soybeans were not cooked long enough. This is hard to accept when you spend 4-6 hours of your valuable time to steam (without pressure) the soybeans. I have done this and there is that transitional stage when they are almost soft enough, but not quite. The soybeans should be a dark beige color and not yellow. Also, when eaten, it should have an almost creamy texture. I recommend steaming them under pressure which only takes 40 minutes.

Q: My natto is dry.

A: I initially thought that natto needed a lot of ventilation for the natto to breathe and to blow off the ammonia produced in the fermentation. So I covered the natto with paper towels and newspaper and then put it in a paper bag. This was a very long path to a dead end which led to not so tasty dry natto. Turns out that natto does not need that much air. So now I use the Double Cling Wrap Method (scroll down to the middle of the post). I poke holes on the cling wrap with a tooth pick so there is a hole every 1-2 cm (1/2" to 1") apart. This is tedious, but I enjoy this mindless repetitive work.

Q: My fermented natto tastes like boiled soybeans and not natto.

A: The temperature of the fermentation was too low. Make sure you are reaching 42C (108F).

A: I do not have a vendetta against the Mitoku Natto Spore Starter, but the spore starter has given me this result. Mitoku Natto Spore Starter has resulted in leathery white natto or unfermented natto that tastes like cooked beans. Make sure to dissolve the spore starter in 80C (176F) water. Or use packaged frozen natto as the starter.

A: Packaged frozen natto starter was weak. Try a different brand of packaged frozen natto if available.  

Q: How much packaged natto starter should I add?

A: When I use the frozen packaged natto, I chop up the package into 9 cubes. For Okame Natto, one package is 50 grams, so one cube is 5-6 grams. One cube will easily ferment 400 grams of dry soybeans (a little less than 1 lb). So a 3-pack of 150 grams will yield 27 cubes, or 27 batches of natto!

Q: What is the conversion rate of Dry soybeans to fully hydrated soybeans (after 18 hours). 

A: For soybeans, I use x2 as the conversion factor. So 400 grams of dry soybeans will become 800 grams of fully hydrated soybeans.

Note: Please use the "Contact Me" or email me directly at nattodad[at]gmail.com if you want direct replies.


  1. I just made a batch of natto that's not stringy. Can I eat it safely? It smells like natto. I fermented over 48 hours(!) I know I was supposed to do it over just 12 hours or so but the first time I saw the white layer on top but no stringiness, so I put it back .. not much improvement after another 12 hours, so I added more natto kinase hoping this will change ... and so on and so forth. It looks and tastes like natto but when I pull it there is no stringiness. Aaahhg my 48 hour experiment! This is my third time trying to make natto at home and every time it is disappointment .... I wonder what Im doing wrong. I used my oven and I put a lamp inside to keep it warm .. :( anyway do you know if it's safe to eat non-stringy natto?

    1. Hi J,

      This is in addition to my previous response, but would you know how warm it gets with a lamp inside the oven? With the setup I use, I can keep the temp around 98F. If you can keep it around there for the first 12 hours, the fermentation will likely succeed. Ideally keeping it for 16 hours would be great.

      Also, not sure how you are cooking the beans. I advice to steam the beans under pressure so the beans are soft. The natto will have an easier time growing.

      As mentioned below, you could be doing everything right but if the starter is not doing its job, the natto will not turn out stringy. If you can get your hands on frozen Okame Natto at the asian market, that will be your best bet on the starter.

      Feel free to post a comment if you have more questions. And thanks for reading the blog!

    2. Hi J,

      I have eaten non-stringy natto without a problem, although it is not as tasty as stringy natto. My only concern from what you have told me is that you added more natto "kinase" (do you mean more natto "starter"?). Adding natto starter midway might add contaminants, if the water used to dissolve the starter was not sterile. So the only advice I can give you is to eat it at your own risk... If it is strictly about non-sticky natto , I have eaten it many times without a problem... again this too I can only speak from personal experience.

      Good luck with the natto! I am probably close to my 100th batch and the first 20 times or so were not stringy...

      What is the starter you are using? I have not succeeded with Mitoku natto starter. So now I strictly use frozen packaged natto as the starter. I keep it frozen and cut small cubes and use that as starters. I did a comparison of two brands and one turned out not so stringy and the other had wonderful silver stings of natto goodness. Surprisingly, the winner was the cheapest, most commonly available Okame Natto. With a 3 pack of Okame Natto cut up into 9 cubes per pack, you can make 27 batches of natto!

  2. I love your commitment but your lack of units when talking about adding frozen natto is frustrating.
    How many GRAMS of frozen beans are you using.

    1. Hey thanks for the comment! Good point on the grams of the starter. I updated the Q&A and Homemade Natto Recipe to include the gram amount. So for Okame Natto, 1 pack contains about 50 grams. I cut it while frozen into 9 cubes, ~5-6 grams each, and put it in a zip lock bag. A 3-pack (150gr) will yield ~27 cubes, or 27 batches.
      My observation is that the amount of starter added can vary without affecting the natto. I have noticed this because in the frozen natto pack, the cubes from the edges of the pack have less amount of natto when cut into 9 cubes. I have used them as starters without a problem. When it bugs me that the cube used is too small, I will use another cube for peace of mind.

      Not sure if I mentioned it, so I added the conversion for Dry soybeans to hydrated soybeans. The conversion is x2 so 400 grams of dry soybeans yields ~800 gr of fully hydrated beans after 18 hours.
      Hope that helps!

  3. Awesome Natto Dad.
    Thanks for making those unit changes.
    I definitely used bought Natto than was required but whatever.

    I've just completed my first batch of Natto and wow. Definitely pungent. I can't believe I slept in my room with that in here!
    In fact the Ammonia smell after 24 hours seems like an absolute relief.
    I had a few temperature control issues but I don't think it was a total fail. One of my boxes had nice sikky strands coming from it, but not the real thick slime ropes that I was watching on Iron Chef.
    It wasn't a thick Natto when I bought it.

    The ammonia smell is reminiscent of some very ripe Brie or Camembert Cheeses.

    I guess could you clarify the consequences of fermenting too cool or too hot, and

    how do you know when you've actually ruined a batch?
    not just not.stringy enough but completely ruined?

    This seems to be far more of a delicate art (except the smell) than yogurt making.

    1. Hi Andrew,

      I agree that natto making nears an art. It took me more than a year and more than 30 batches to get it right. I am easily over a 100 batches and it still does not come out right from time to time. Out of all the fermented foods I have made, it is definitely the most finicky.
      I have come to think that excessive ammonia smell is also a sign of poor fermenting conditions. It should be pleasantly pungent and not nose piercing. The reasons for this may vary.
      As you mentioned, I have also noticed that if I start with a not so stringy natto starter, the fermented natto will not be stringy. The other tricky thing is that I have used my own fermented natto as starter and I've had problems maintaining a stringy starter. I do not recommend this as introducing a contaminant is easy. As for the non-stringyness of my starters, it is a total mystery but I have dug some research papers that there may be a virus that attacks natto in the wild which causes non-stringy natto. It is a big problem in commercial natto producers from what I read until sterile techniques were developed.
      I think that making it at home, fermenting too cool is more of a problem as maintaining close to 40C (104F) for 12+ hours is difficult without proper equipment.
      Fermenting natto too hot may happen but a handy thermostat would show that.
      Also, I cannot stress enough that undercooking the bean will result in weak natto. If the natto bacteria cannot extract the nutrients from the soybean, the natto will not grow.
      Ruining a batch to me would mean poor sanitation and or contamination. If you do not see an even natto growth on the soybean and it does not smell like natto, I would put it in the compost bin.
      Happy natto making and let me know if you have any more questions or need more clarification.
      Natto Dad

  4. Does the Natto still contain Vitamin K2 even though it did not go stringy

    1. That is a very good question! I do not have an answer but will look into the literature to see if that can be answered.

  5. I have been (damn) lucky and have pulled off about 10 good batched of natto...THEN ...the last two batches have been...One batch looked weird and smelled weird. Looked Weird: kind-of a white, moist flaky substance...all through out in between the beans kind-of and it smelled...wrong...not ammonia exactly. I threw it out. Then The next batch came out the same but less of the white stuff and smelled better...I ate that and I was fine But Now I have a batch again that has a lot more white "stuff" again....ever heard of this?? I can;t seem to find any mention of this. I can email a picture! haha! :-) Any help would be greatly appreciated. I had a three foot long clot in my leg last year and it was my second in life and I am only 43. I insisted on getting off the thinners, they were wreaking havoc...But my deal to myself was that the thinners would be replaced with natto. Thank you so much for your time!

    1. Hi Emily,

      Yes, I've had the same problem which I wrote under "Q. My natto looks leathery and dry-" above on the Troubleshooting Guide. Not knowing what your fermentation situation is, it is really hard to say. If you have not done so already please read the "Homemade natto recipe" and the "Troubleshooting guide". Ok with that out of the way, did the last two times you make it coincide with winter natto fermentations? I used to get this problem when I could not maintain high enough ferm temps. If you are using a lamp or something that outputs the same energy, the average temp of your ferm will be lower in the winter due to the lower ambient temp. Most ideal will be to maintain it at 38C-40C (100F-108F). You start to get into the low 30Cs and it can start to get funky. Let's keep this conversation going and figure this out! Emily, hope natto will help alleviate the clot. Not being a doctor, I cannot make any medical suggestions but I truly believe in the healing power of foods so please keep searching and discovering foods that will help you. Natto has been a great fit for my health, which led me to write this blog so people like you could make natto at home and find success.

    2. Forgot to mention, please send me pics! Will put it in the Troubleshooting guide and hopefully when we find the solution, that will get posted too!

    3. This comment has been removed by the author.

    4. By the way...How do I get these photos to ya?? :-)

    5. THANK YOU!

      I had an after thought as afar as descriptive words go for the flaky white stuff. It's kind of like ...cheesy...It's not dry in other words and the slime is forming just fine so the moistness of the Natto seems correct. Which incidentally, is what prompted me to ask the question because the DRY flaky thing I did read about.

      I was pondering after I wrote you (which I did after reading your Fantastic and greatly appreciated and VERY helpful trouble shooting page) and it started to occur to me that this started at the seasonal change (this winter).
      Our house is heated by a fireplace and the kitchen can get very cold. I have a standard simple cheap yogurt maker (no temp controls, it's just on or it's just off) that I put the soy beans into after the (Pressure) cooking of them. In the warmer months I checked the yogurt maker to just see if it was working as advertised and it was keeping a steady 114-ish degrees so I didn't think of it again.

      BUT I have not checked to see what it has been doing now, in winter. DO you think it may be colder temps???
      Would it be a waste of time to test this theory in other words. :-)

      Also I am at about 7500 ft, high desert. I don't know if or even why altitude might make a difference but I thought it worth mentioning at least.

      Also I have used the Recipe posted on http://www.naokomoore.com/2012/05/making-natto-fermented-soybeans-from.html and as i said it has been so easy and consistent up until now.

      THANK YOU AGAIN for your time and sharing! I have been using the Natto every day for about 6 months. I did have a laps when I had the bad batch and my routine got broken. ( I am not good with routine HAH) so it took me about a month to get going again. It was really amazing though because I was not paying much attention to time or not eating the Natto and yet I was feeling worse and worse and worse just in every way possible, digestion , aches and pains, tiredness etc. and it FINALLY occurred to me that It had gone almost a month since I ate the Natto. I started back up and with in a week everything started getting better again. I am half Japanese. I do feel there is a bit of genetic familiarity that my body is responding to too but who knows!!! The White half is the half that gives me blood clots. hah!!

      OKAY! Didn't mean to write a damn book here! Thank you again and I will send pictures tonight!


    6. Hi Emily,

      Yes, if the fermentation coincided with the cooler winter temps and you have the same setup, lower temps are a likely culprit. Also, I hope you are able to steam the soybeans in a pressure cooker. At high elevation, it takes longer to cook things, is that right? You should be able to squish cooked soybeans with your pinky and thumb when properly cooked.
      I have also noticed small changes to my diet that have helped me feel healthier. I am not allergic to anything and will eat anything, but I have cut my intake (not stopped eating) simple sugars, unprocessed dairy- milk, unfermented flour foods ie crackers and excessive intake of meats and fats. That seems to have made a difference. Having said that, I love to eat so I still eat everything without any restrictions. I mainly eat a plant based diet.

      You can send me pics to
      (replacing the [at] with @)

      Keep up the natto making!
      Natto dad

  6. I just tried your recipe and so far my natto looks ok, I am letting it cool. I used a dehydrator w/a bowl of water instead of the oven. My question is about the color of the beans. Most of them are pale yellow and a few are the caramel color that natto usually is. I'm using Laura's soybeans and steamed them as you instructed in a pressure cooker.

    1. Thank you for the comment! Let's see as for the color, they should be caramel color. If the top layer is caramel color and the rest is yellow, it might be due to dehydration. If all the beans look yellow, it may be undercooked. After done steaming in a pressure cooker, the soybeans should be soft enough to squish between your thumb and pinky and should almost have a creamy texture when eaten. Please note that when steaming in a pressure cooker, the cooking time starts when you build pressure and NOT when you close the lid of the pressure cooker.

      When done fermenting, the soybeans should smell like natto and should have a white/translucent film on the beans and should be sticky when stirred. I am not sure how hot the dehydrator gets, but should stay between 38C-42C during ferm. If cooler, the natto won't grow and higher will probably dehydrate the beans or kill the natto.

      Hope that helps. Also I would like to know if you get a notice when you receive this comment or if you have to physically check back into the my natto blog again.

      Natto Dad

    2. Thank you for the reply. I think I did not cook the beans long enough,they are soft but maybe not soft enough. I think for a first attempt the natto came out ok but I think I'm going to try again! I didn't get a notice and had to check back to see if you replied.

  7. Can nattou ferment more than 48 hours? Like is it safe? The first two days it had a bad ammonia smell and I decided to leave it for a miracle I came back to it this morning and it's what it should look like and the ammonia smell has died down in just scared I messed it up bad..... any pointers ? Hope to hear from you soon!

  8. Hi Sean,
    -As for fermenting 48 hours, I feel that it is too long. When the fermentation is finished, the soybeans should have a white translucent growth that is stringy throughout on all the beans. This should happen in 24 hours if the fermentation conditions are optimal. At the beginning, I also had prolonged the fermentation hoping for a miracle but it never turned out right. Excess ammonia is a sign ot the natto bacteria struggling. Better to look at your fermentation conditions and find to optimize the process.

    As for the safety of eating it... if it doesn't look like natto, I would not eat it. There is a risk that you are growing rogue bacteria not knowing your sanitizing procedures on the prep stage. So the best I can say is eat at your own risk. Or maybe don't eat it and try again until you make a good batch would be better!

    Please keep trying and hopefully you will make great natto! It took me more than thirty tries to make decent natto so don't loose hope.

    Natto Dad

  9. Hello NattoDad,

    If after you make natto, can you just put the whole glass casserole dish in the fridge with the little holes punched in the 2 layers of plastic wrap or do you need to cover it with more plastic wrap so it doesn't leave an odour in the fridge, ...& possibly spoil other food that is already in the fridge.

    Thank you. ☺

  10. Hi, thank you for the nice instructional youtube video. I managed to make natto from white beans and the taste and stringiness was ok. I left a small batch from the first portion as starter for the next batch but the second batch didn't turn out as stringy as the first one. You use a frozen package as starter, I suppose you have already tried which I just did and you had the same result, am I right? Regards, Jozsef

    1. Hi Jozsef, I have kept natto from a batch and used it on subsequent batches. The most I have made it is three generations, with the first generation being made from packaged frozen natto. It may be due to contamination or weaker natto. I have read that virus contamination used to be a big problem when they started making commercial natto. As for natto becoming weaker, if the first fermentation was not optimum, I could see the natto becoming weaker on the second batch.

      If frozen natto is available, I would keep using that as your inoculum. If not readily available, earlier generations seem to be stronger, so I would freeze enough for a few batches and use that instead of keeping just enough for one successive batch. Hope that helps!

      Natto Dad

  11. Thank you for your reply, I will try to freeze portions of the best batches and see how they perform as starters!

  12. I think I know why Natto doesn't get stringy and snotty but does get sour.
    The Natto bacteria (Bacillus subtilis) is really vulnerable to take over by lactic acid.
    Lactic acid is made by the Lactobacillus bacteria which even come from the air we breathe, hence when making sauerkraut the traditional way there is no need for bacteria starters. The Japanese when making Natto are very careful not to let the Natto even come in contact with skin cells. So sterility is so important to making sure the Natto bacteria grows NOT the Lactobacillus bacteria.

    1. Thank you so much. Just made a batch that after 22 hours smelled like bread yeast... I guess I'll have to discard it. Tried using the previous batch as a starter

  13. Thank you natto dad! I followed your instruction and it came out great! I used the natto starter from amazon since I didn’t have frozen natto. It was stringy, fresh bean flavor, so much better than store bought one.

  14. Natto Dad!!! You are so generous to have made this blog. I really really appreciate it!! Just wanted to say thanks from the bottom of my healthy microbiome :-)

    1. You are welcome Katharine. And cheers to your healthy microbiome! -Natto Dad

  15. Hello Natto Dad. I am Abig Fan of yours. I have this issue: I just made natto and it smells strongly as ammonia. I understand this might be of temperature problem? Even if I used the regular temperature? What else cold be causing this? And also, can a ammonia smelling Natto be eaten?

    Thank you in advance for your help

    1. Hi Natto son, haha nice name. Yes the biggest culprit would be temperature. It is best to hit 108F (42C) at some point in the ferm. The list goes on which can include, if you are boiling instead of steaming the beans and a weak starter. Mark all the points that your method is defferent from mine and you will have to troubleshoot each one. Natto is very fussy so you will have to be mindful on how you are making it.

      Please write me a direct email as I do not think reply to comments are prompted in any way.

      Hope it goes well!
      Natto Dad

  16. This comment has been removed by the author.

  17. Hi there! I find out few things that you don't show in your video tips. Hope you re-film or add it as subtitles ;) Answer to those who fail to make natto from starter. I fail 10 times until i change this in my steps:
    1) After you pressure steam beans, put them in clean tray and cover them by wrap without holes and let them sit until they cool down to 40-50° and only after that add an starter wich you dissolve in 70-80° hot water.
    2) After i put them in fermentator i get my clock on 6hours, then i small down my heat emmiter on 1° because natto start to create it's own heat (dispassionate >39.0° - <39.3° to >38.0° - <38.3°)
    3) Be sure that you pre-warm your incubator before you put it inside to ferment.
    I also keep humidity around 75%.
    4) Don't use LDPE wrap (even you make holes in it)!!! Only PVC for food. Why? Because PVC give food a breathe. Otherwise it getting bad.
    Good luck!
    \\Y. (Russia)

  18. Hello! Thank you so much for your YouTube video and this blog.

    I'm on my second batch of natto that I made after watching your video. Both turned out great! Super tasty, stringy, moist and perfect.

    I don't like plastic to touch my natto, so on the second batch I used cheesecloth in glass containers with glass lids. That worked just as well.

    However, I also made a batch of adzuki beans natto at the same time. This one is stringy but smells like ammonia. So I did all the same steps as I did for soybeans and the adzuki only have the ammonia smell.

    Can the ammonia ones be eaten?

    I read on another site to add vinegar and then it can be eaten. Other than the smell it looks stringy so it fermented. I did taste a few earlier today and I feel fine.

    And a side note, I use my programmable kiln to ferment. It works great because it counts down the hours left and shows the exact temperature.

    1. I ended up just tossing the adzuki bean natto. I tried the vinegar but it tasted bad. Must have been something about using adzuki beans.

      On my third batch of soybean natto making today. Thank you so much, I rewatch the video every time.

      My cheesecloth method works great. I'm glad to not use plastic on my natto. That was one of the reason I wanted to start making natto. I want to reduce the plastic in my life and in my food.

    2. Hi Natto Dad or Saya, Can natto that smells of ammonia be safely eaten? My natto has strings but is a bit soggy. I think I left too much liquid in after the boiling. I let it ferment for about 27 hours on the instant pot yogurt setting with the lid slightly ajar.

    3. I think it's better to just start again. Did you try the vinegar? I've never had it happen with soybeans. I usually ferment for about 20 hours. I don't use the plastic wrap but boil my cheesecloth and cover with that and then a loose fitting lid. I don't want the plastic on my food.

    4. Saya, after putting it in a glass dish, do you wait for the natto to cool down,
      or do you immediately cover it with a cheesecloth and put it in the incubator?
      is cheesecloth wet when you do this?
      do you only cover soybeans or do you cover top of the dish(under the lid) with second cheesecloth as well?
      i'd like to end with plastic too, it leaks to the food.

    5. Hello Skyless, I add the natto bean starter into the beans once they are around the 105 degrees then I put the boiled cheesecloth over the beans. The cheesecloth is squeezed dry. I put two layers of cheesecloth and then the glass lid. I let the cheesecloth hang over the edge so there is a little air flow. Trying to mimic the hole punching in the plastic and not have a tight fitting lid. I use a variety of glass dishes to ferment in. Including ones with a glass lid. I don't think I can put a picture. I hope this makes sense.

    6. May i know what starter do you use? What company? I've tried nattomotto and never turned well. The same enviroment but used frozen natto and it worked, but unfortunetly i can't longer get frozen natto in my country ;/

    7. My starter is the frozen natto beans from the store. I haven't tried the powdered kind. So I don't know where to buy it. I've also saved my natto to use as starter. Maybe you can find someone to some of their natto to use as starter.

  19. Dear nattodad,
    I followed your youtube video instruction
    My natto comes out with a lot of strings, smells less ammonia, and tastes less bitter.
    I am so grateful for your detailed advices. Thank you
    However, even though there are a lot spiderweb when I stir,the string seems doesn't strong enough to pull all the neighbor beans up.
    Do you know the reason why?
    Thank you

  20. Natto Dad, You state to let the beans cool 20 min. after pressure cooking. Can you please give us a temperature that the beans should be at when we add the starter. My first batch was superb, the second not as good, and I'm wondering if it cooled too much or was too hot. So please give a temperature the beans should be between for the starter to be added.

  21. I just accidentally heated my nearly finished natto to 90 C degrees, shortly and I cooled them off quickly. It seemed like the stringiness increased a lot, right then, I hope that they feel good in the fridge now.

  22. This is such great info. I have had a couple of fails and some OK, but none spectacular, so I will incorporate some of the instructions here. I usually end up with water in there from using other methods than pressure steaming.
    One q I didn't see here--I really like hikiwari natto. So last batch, after the beans were soft, I rubbed off all of the skins (which is as tedious as it sounds) and that got the beans to either shear in half or to crumple to hikiwari size. There has to be a better way. Advice appreciated!

  23. Hello,
    I just started making natto and the nattos didn't not come out sticky but smells just like natto. I am thinking this will not be my first bad batch. But is it still OK to eat? I just didn't want to waste a whole batch. Thank you

  24. When I make natto it doesn't get very stringy but it does get it somewhat. And when u mix it around it gets the slimy texture like the one you buy. So I save some of the home made natto and make more using that. I can get many batches doing this but today it went wrong. I had too much liquid in it, and it smelt way wrong, like other bacteria was in there so I threw it out. I have noticed it gets less stringy with each batch doing this, so I don't know the exact issue. Temp might not be optimal because I basically boil a large pot of water and put that in the oven for heat. It's still very warm after 12 hours but I think maybe overtime using natto from each batch to make more, other bacteria start growing. I think I'll probably just buy natto, it's less guess work, higher quality. Maybe more expensive but hey at least it's supporting japanese workers, they probably deserve it more than some americans.

  25. I saw one of your videos and though "how hard can this be?" - Well, I found out. My errors included:

    Not pressure steaming the beans (I boiled them in a rice cooker)
    Not cooking them long enough. (didn't squish easily enough)
    Using lower temp water to start the spores. (China brand from ebay)
    Setting the incubation temperature at 37C.
    Over incubating. 24-27 hours.

    Results? Not very favorable natto with tiny threads that smell of ammonia. Still I'll eat some until the weekend when I will try again. Your blogs and videos are a great help and inspiration. I am starting to love ballilis subtillis! I am looking forward to making making miso with Aspergillus oryzae - perhaps soy sauce and even sake. If you have experience with these, please post! (Oops, I just now found the koji tab. :^)

  26. I have multiple recipes and had success with: small whole soybeans that I removed hulls from after soaking (very labor intensive, took a long time rubbing/stirring and skimming off hulls), pressure cooker, powdered Takahashi Nattomoto (available through Amazon). The recipe I followed said to add sugar and salt to water that natto powder is dissolved in to kick-start:
    " 0.1g Bacillus Natto bacteria
    ● 1/4 teaspoon salt (natural salt, if possible) A little salt increases stickiness and improves the
    ● 1/2 teaspoon sugar (brown sugar or molasses, if possible) Sugar aids the activation of natto bacteria spores and will help fermentation."
    and watch for white film covering beans, which did happen. The second time I used pre-hulled split soybeans sold as for making tempeh, miso, natto. I also tried different powdered starter: Kawashimaya. Very little white film. This one smelled strong of ammonia and very few beans were brown most same color as when they went in. I used a bread proofing "oven" at 106 F

  27. Hello Nattodad, and thank you for your effort to clear all the problema that could arise. My questione Is about bitterness. What could be the reason of a very bitter natto? Thank you