Wednesday, May 15, 2013

Homemade Natto Using Packaged Natto -Batch #37

Updated May-2020. Please read again if you came before.
Note: Please use the "Contact Me" or email me directly at nattodad[at] if you would like a reply. I will not reply to comments made in the "Comment" section.

Day 0, 9pm
-400gr Kotsubu Laura's Soybean 16-20 hour soak, summer time 25C (77F). 20-24 hour soak, winter time 10C (50F).
Note: I prefer longer soaks over short soaks. So even in the summer, my tendency will be to soak it the night before even if I am steaming the soybeans the next day in the evening.

Day 1, 630pm
-Place beans in strainer and discard hard beans.
-Set up pressure cooker with water and place ramekin/small plate in the pot.
-Once boiling, put soybeans into strainer and place on top of ramekin inside the pressure cooker so the beans are not touching the water.

-Close lid on pressure cooker and build pressure. (My pressure cooker starts to whistle, at 1.5 bars or ~21 psi).
-After it builds pressure, set timer to 40 mins and lower range temp to medium-low. The Taylor thermometer is really handy as a timer and as a thermometer.

-While cooking, set oven temp 104-108F (40-42C) with a heat source (yutanpo, lamps, pre-heat, etc). In my case I use a 150W Ceramic Infrared Heat Emitter (plus a socket power plug) connected to a Digital Controller Thermostat. I now set the temp to 108F (42C).
Note: Due to fire safety reasons, use at your own risk.

Alternatively, you can use a single coil cooking range (like this one) inside on the very bottom set to warm, and plugging it to a Digital Controller Thermostat
Note: Due to fire safety reasons, use at your own risk.

-Place a pot or soup plate with water on the bottom wire rack (for humidity) and leave the top wire rack empty to place the baking dish later.
-Sanitize baking dish for 20 mins with 1 TBL of chlorine and fill to the rim with water. Discard and rinse with water.

Note: Natto fans have suggested other sanitation methods such as Heat, Steam, and Sterisan. Please use the method that fits your needs.Using Boiling water over the trays and draining works well.

-Also boil two spoons in a pot for 10 mins. Dump boiling water into the glass baking dish and discard water after 5 mins.  Alternatively, you can leave the two spoons in the baking dish that is sanitizing with chlorine. You will have to rinse with water afterwards so this is less sanitary. 
-When the 40 mins are up, place pressure cooker aside to cool for 20 min.

-After 20 min, open lid and put cooked soybeans into the glass baking dish. The soybeans should have turned from a pale yellow to a light caramel/beige color.
-Put a cube of frozen packaged natto (1/9 th of a package, will work with 1/12th of a package or 6gr ~ 4gr, 5gr avg.) into the hot soybeans and make a little mound of hot soybeans on top to cover the natto with the sterile spoon. Wait a minute or two until frozen natto cube thaws.
Note: I usually keep the packaged natto in the freezer and cut it into 9 frozen cubes per 50gr pack which are kept in a zip lock bag for later batches. So a 3 pack (150gr) of Okame Natto frozen natto will yield 27 batches of natto!

-Mix the melted packaged natto with the sterile spoon and add 2-4 soup spoons (about ~2-4 measuring teaspoons) of the hot water from pressure cooker. Add enough while making sure it does not puddle on the bottom. Mix the soybeans, packaged soybeans and water with the sterile spoon until well incorporated. 
-Tightly wrap the cling wrap and poke holes with a tooth pick all over the surface of the cling wrap. Then, detach from edges and rest cling wrap on top of the soybeans.

Double Cling Wrap Method: One on top of soybeans, second one on the top tight on dish. Creates an air pocked in the middle slowing drying of soybeans. I poked holes on both wraps with a toothpick.

-Cut one more piece of cling wrap and wrap tightly on the baking dish and poke holes. This will form an air pocket that will maintain the moisture on the beans. Cool until it is luke warm and then place on the top rack of the oven.
-I will leave a soup plate or shallow pan with water on the rack below the natto dish to maintain moisture in the oven. Note: Shown in the pic below is a pot, which is too big and not needed.
-Leave the natto to ferment for 16 to 20 hours at 38C-42C (100F-108F)

Day 2, around 3 pm 
-Take out natto from oven and place at room temperature on the countertop. Cool before putting into fridge. You can leave to cool anywhere from 1 to 5 hours, I usually put it in the fridge after dinner or before going to sleep.

-Natto is finished fermenting! There should be a pleasant natto aroma with a slight hint of ammonia, but should not be overpowering. If eaten at this time, it will have a sharp taste. The threads should be thick, sticky and silky when pulled. They can be eaten at this time.

The threads should be thick, but should form really long threads when pulled.

-Refrigerate and let it rest for 3-5 days in which time the natto will become mellower and will deepen in flavor. It will keep in the fridge for up to 2 weeks. If there is still any left, they can be put in the freezer. Time to eat natto!
Note: After two weeks in the fridge, the natto will form animo acids crystals which are texturally a bit sandy akin of the crunchy bits in aged parmesan cheese. If the sandy texture is not desired, natto can be moved to the freezer  after about a week. 

Natto in its full glory

Natto should have silky threads that are thick when initially mixed. When made successfully, the threads will be silky even after adding liquid seasoning such as shoyu and mentsuyu. I also have made so-so natto which is silky, but looses its threads when shoyu is added. A few thoughts on this on a future post.

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


  1. Thank you. Your blog has helped me make pretty good natto. I also had very little biofilm (neba neba) when I made natto from the spore, but I found that if I then extract the bacilus with hot water from a few natto beans from a previous batch (made also from the spore), the ‘neba neba’ increased drammatically. Also using containers that are hydrophobic like styrofoam, polypropylene, and wax paper seemed to help.

  2. Love your blog!
    Question: if I make too many beans, more than I want to ferment at that time, can I put the excess beans in the freezer, and use them later to make natto?
    Meaning: defrost, reheat, mix natto starter with them, then let ferment per directions. Your opinion is valuable to me.

    1. Hi mz beastle, wow it took me while to reply. Hope your natto making is going well. I have not done this, but I do not see why this would not be possible. My two concerns would be contamination from the reheating and a defrosted texture of the soybeans. Please give it a try and let me know if you have any insights. Thank you for visiting the blog.

    2. Well, I never did do the "frozen cooked" soybeans, because another natto lover said in all probability the freezing would destroy something in the bean, making it not acceptable to the natto bacillus.
      However, your information has helped me a LOT!
      My latest issue was using 3rd or 4th generation natto from my previous batches. For some reason, the finished product was not sticky. So, I broke out the store bought stuff as you suggested, made another batch, and it was out of this world neba neba! I mixed it with the barely sticky batch, and I consumed it. It was still delicious. And stringier!
      Thanks again for your great natto website resource.

  3. I picked up a combo pressure cooker/yogurt maker and was hoping to start making natto by doing the pressure steam in an insert over water, followed by the fermentation with the yogurt setting (100 degrees F) in the main container. Given that this is a semi sealed container, do I still want to cover with wrap and leave semi open? ( I picked up the Instant Pot with Natto in mind)

    1. Thank you for reading the blog! To answer your question, you will know by looking at the surface of the finished natto. It sounds like you have a very nice setup so hopefully you will be able to use it as is. If the top layer looks drier it will be better to put a plastic wrap with holes right over the beans when you start the fermentation next time. You will know if the top layer dried because the beans will look darker or will become hard. In the most ideal condition, the top layer should look the same as the bottom layer.

      Hopefully that helps! Keep experimenting and best wishes on your 2016 natto making!

      Natto Dad

  4. Welp, just to follow up the instant pot worked very nicely. Soak 300-350 grams beans Thursday morning in four cups of water, just drain them from soaker to mesh steamer insert Friday, and pressure steam for 45 minutes with a 20 minute cooldown in 1.5 cups water.

    Then 1) Boil bowl to hold steaming liquid, spoon for same, and wide paddle to stir with
    2) remove steamer, set aside, dump steaming liquid into ramekin, dump beans into Instant pot
    3) dump (lazy here) full package of store bought natto into pot, use paddle to stir and mix well with steamed beans
    4) add three tablespoons or so of the bean liquid
    5) and set the instant pot to yogurt setting for 24 hours.

    That sounds complicated but takes about 20 minutes in all. Finally Saturday morning, boil the lids, a couple spoons and paddles, and the first glass storage tray. Every 5 minutes remove the current tray to cool, drop the next tray in to boil, and load the cooled tray with 1/3 to 1/4 of the beans. Total time elapsed about 30 minutes but with lots of time for chores along the way.

    The output has been fine, three or four glass trays of four servings each. Let them rest in the refrigerator for two days, then freeze all but the next to be eaten.

    I'm not sure I'd bother without the pressure steamer/yogurt maker though. Having it all be one pot with minimal fuss is what beats the local market in Japantown San Francisco at three packages for USD 2.00.

    1. Thanks for the input! I am glad you found your groove with your setup. Natto on!

  5. Hi Natto Dad, Thank you for your website, it has been a real help in making good natto.
    Although it has neba neba, there isn't as much as yours in the photo.
    Wondering about using store bought natto here in Australia as starter. As it is all from Japan, people here worry about it being contaminated with radiation.
    What are your thoughts? Do you know which brand of natto is safe? We use spores made in China.
    Thank you again for taking time to help us all.
    Mary Rose

    1. Hi Mary Rose,

      I totally missed your comment. For a direct reply please use my email written on the top right side of the blog page. I believe the cheaper brands use US/foreign grown soybeans so there should not be any radiation. The ones that are "Kokusan" using Japan grown soybeans mau be an issue. I have not clue how strict the radiation standards are in Japan. Hopefully they are strict enough the keep the Japanese population safe.

      I personally use Okame natto. It gives me the best nebaneba and it is super reliable. I believe it is one of the most common available too. I have used spore started but have never succeeded in making silky natto so my preference is towards the frozen natto.

      Hope that helps and sorry for the late reply.
      Natto Dad

  6. Hello Natto Dad, yourwebsite is very helpful, i want to ask something, is it okay if i make natto with self-made styrofoam incubator? I used natto spore and it was very stingy and had thin string...

    1. Hi Stepfany,

      Yes, I am sure you can use a styrofoam incubator. What is your heat source? Temperature is important so find a method that will give you 100F (~38C) for at least the first 12 hours. If possible for the entire duration of the fermentation ~20 hours. If available in your area, use frozen packaged natto as your starter. I have never produced a silky batch using spore starter. Need to work on it this winter.

    2. Thank you for your reply, i'm very glad because i don't have an oven, i used 15watt lamp, and i had made sure the temperature around 40c

    3. Thank you for your reply, i'm very glad because i don't have an oven, i used 15watt lamp, and i had made sure the temperature around 40c

    4. My only concern would be to take extra precautions with the heat source so it does not touch the styrofoam. I am not sure how flammable styrofoam is but it never hurts to be on the safe side. Hope the ferm goes well and send me pics of your natto! If you need a direct response you can contact me at my email written on the top right of the page. Just out of curiosity, did you get a message when I replied to your comment or did you have to check back to my blog?

    5. I checked back your blog, sure, i'll send you pics

  7. Hey, Natto Dad, this blog is great! It helped a lot.

    I have a question: in your video you talk about that 4 days later is more sticky. This 4 days are continuin fermetation or ir the fridge o at room temperature?


    1. Hi El Favricante, not sure if I had replie to this. So off from the fermentation, it goes into the fridge right away. I like hoe natto tastes between 4 days and a week and a half in the fridge. After two weeks, portion out and freeze. -Natto Dad

  8. Hi Natto Dad,

    Received my Mitoku starter in the mail today (before I found your blog, ugh!) and am about to set out on my first natto-deavor. A couple of questions for you (apologies if you've already answered some variation of them):

    1) Is it necessary to soak your beans if you intend to pressure cook them?

    2) Have you ever used something like a sous vide (water bath) to keep the temperature precise? This would involve sealing the beans up (in a thin layer) of the vacuum packs and placing them gently in the water bath.

    Thoughts on this? Not sure how important the cheese cloth and such are in your set up.

    Thanks for this blog! Good stuff.

    1. Hi! Thanks you for visiting the blog. Please make sure to check my youtube video as well, found by punching in Natto Dad.

      1)When pressure steaming, which is putting the soybeans in a strainer and suspending over the boiling water, the beans have to be soaked for at least 20 hours. I have never tried putting pressure steaming dry soybeans but I think it would not plump up and cook in time.

      2)I have not used a sous vide to make natto as I do not have the setup to do so. I am aware of this cooking method. You could use the water bath for heat but the natto needs air to grow being aerobic so vacuum sealing it might suffocate the natto bacteria. If the fermenting container could be suspended in the bath, I think it would work nicely.

      Not covering the top with plastic wrap or cheese cloth will dry out the surface and natto does not grown well when dry. So I suggest covering it while allowing a little bit of air to get in.

      Hope that helps! You can also use my as I do not think you get reply notifications when commenting on the blog. Let me know how it goes! -Natto Dad


  9. Hello Natto Dad, congratulations for the blog that is very useful.
    I would like to know: Can I use the yogurt maker as an incubator (instead of the oven) for fermentation of the natto? thank you

    1. Hi Maria, you can. The holding temperature might be different between yogurt makers. Optimum for natto fermentation is between 98F and 104F.

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  12. Hi thanks for your very useful blog!

    I just made natto using mitoku powder, using a yogurt maker ... it tastes like natto, but it is not sticky enough! You say you refrigerate your fermented natto for three days for deepening flavor - does that process also help increase nebaneba stickiness?

    Or was anything wrong with the yogurt maker I used? It's T-fal y232 ... I can't control the temp but I'm assuming it should keep the temp around 40c.

    This is like the 8th batch of natto I've tried over years ... it's always like this, not sticky enough. I dream of tasting those super sticky natto ... mounds of it!

    Next time I will try okame natto ....

    1. Hi J, if you have not done so already please check my youtube video on how to make natto with a spore starter. That may help. I've had the same exact problem. It may be because the spore starter was not dissolved in 80C water. I have always wondered if there are old batches of spore starter floating around in the internet as well which may affect the viability. Storing it unfortunately does not increase the threads. Having said that, my best batches are made with frozen natto. Please email me on the "Contat me" on the top left so you don't have to keep checking the blog for my reply. Happy holidays! -Natto Dad

  13. Thank you! I just watched the video! Your efforts to show the world how to make natto is so completely appreciated!!!!!! And the batch of natto you made in the video is like a DREAM ... I wish I could have that much good natto in my kitchen soon ... THANK YOU THANK YOU THANK YOU!

  14. Hi Natto Dad!I have made my first batch with a yogurt maker:I had put the beans in a big glass jar, After 21 hours of fermentation turned out pretty good (biofilm Neba-Neba) in the 3/4 upper part of the jar (at the top), instead, in the bottom the beans seemed not fermented, no biofilm, no stringiness. So I keep the upper part and discarded the bottom. Can I eat safely this Natto or I have to discard all the batch? And, another question, can I use my DIY Natto as a starter next time or I have to buy It? Thanks you are the best!!!

    1. Hi Allessia, you should be able to eat the fermented part. It sounds like to bottom did not get enough oxygen to get. Next time you can use a shallower container and see how it goes.

      As for using your natto as starter, it might get contaminated after successive generations. So it is better to make a large quantity of gen 1 natto and freeze it. Then use that for any new batches. If you have any questions please email me. Thanks! -Natto Dad

  15. I just want to say THANK YOU. The information you gave are very helpful to me.

  16. Hi Sir. I made a batch, it tastes like natto, little amonia smell, little bit bitter after 20 hours of incubation at 34,5 to 39,5 celcius. But it is not sticky, struggle to use chopsticks. Why is that? The only modification with your method is, I covered the fermentation with double filtering cloth instead of plastic. I have steamed the cloth to sterilize. Also I use beaten soybean for smaller size. Thank you.

    1. Just read it must be the water temperature used to dissolve the starter. So, will making new batch with the first mentioned batch as starter results in stickier natto?

  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. Hi. I have a question. After let natto be cool down in roon temperature, its time to put it in the fridge, so do i need to cover natto with a plastic wrap or must keep small hole for it to breath? Thank you.

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  20. Hi, I have 2 questions:

    1. Will the cooking time different if I use electric pressure cooker?

    2. Can I use dehydrator and set the temperature at 40C, also put a bowl of water durinf the fermentation process?

  21. Hi Natto Dad. I am wondering if I can change your recipe to just 1 Cup Dry Soybeans. If I did, would I use less Natto Spores? (I don't have frozen natto where I live)

    Also, can I make your recipe with Black Soybeans the same way? is it the same soaking and cooking times?

    Thank you. Really love your video and Blog!