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Natto is a polarizing food. You either love it or hate it with no in-between.
It has a texture which most in North America are not used to, has an acidic smell and is covered in a slimy coating which tends to through people off when they first see it.
On the other hand if you give it a fair chance it is a delicious and healthy food. It contains a high amount of protein, contains PQQ and nattokinase as well as a host of vitamins and minerals. It can eaten in a variety of ways besides the traditional method of served over warm rice with soy sauce and mustard.
There are three ways to make your own natto you can use a packet of store bought natto, use a starter powder or you can make it from scratch.
Make Natto from a store bought packet
This method of making natto uses backslopping which is a method of fermentation where some of a prior batch is used to inoculate the next batch. With natto this can be done by purchasing a frozen packet of natto from your local grocer and using it to make a batch of homemade natto.
Although natto made this way will work consistently when commercial natto beans are used you should not try to use this method using your own natto beans as the culture can get contaminated quickly and cause the natto beans to go off, get moldy or not produce the sought after slimy coating indicative of natto beans.
The benefits of making natto from commercial natto
Cheap to try
This method will cost you the price of a packet of natto and two cups of soybeans. You will get at least four cups of natto to eat which will be a fraction of the cost of buying it premade.
Easy to do
Natto made this way is really quite simple. You soak and cook the beans then mix the packet of natto into the beans thoroughly and ferment for 12-24 hours depending on temperature and how you like your natto. Click here for a complete recipe in how this is done.
Will taste the same as store bought
The culture which commercial natto is made from is very controlled so there will not be many stray bacteria in your natto to cause the flavor to be altered. You are essentially getting pure bacillus natto cells from the natto package to ferment your soybeans.
How to make natto with a store bought package of natto
Equipment:
- shallow non-reactive pan
- stockpot or some other large cooking container
- wooden spoon
- colander
- bowl large mixing bowl
Ingredients:
- two cups of soybeans (small ones work the best but any will do)
- one package of store bought natto
Prepare the beans
Soybeans are sold dry so they need to be soaked to allow then to rehydrate before you cook them. Place them in a container which will hold at least twice the volume as the beans then fill the container to an inch or so below the lip with filtered cool water. Let them soak for 8 hours or so (usually overnight).
Once the beans have been soaked strain them and rinse them in cool filtered water. Put them in a large stockpot or other suitable container and fill the pot with water.
Boil the beans until they are soft enough to crush with your thumb and ring finger easily. The softer they are the easier it is for the bacteria to ferment the beans but too soft and they will not hold up to stirring.
Once they are done drain the remaining water from the stockpot. Do not rinse the beans!
Inoculate your beans with the natto package
Place the beans in a shallow pan and let them cool to 115˚F.
While the beans are cooling thaw a package of frozen natto.
Once the beans have cooled and your natto package has thawed mix the package into the beans well. Ensure all the beans have been in contact with each other.
Cover the beans with plastic wrap and place the container in your incubator for 12 hours.
After 12 hours you should see a white growth on the surface of the beans. This indicates your natto is ready. Remove the container from the incubator and take the plastic wrap off.
Scoop out the fermented natto into serving sized containers and place in the fridge to cool.
Natto is best once it has a chance to mature in the fridge for two or three days but it can be eaten once it comes out of the incubator.
After two or three days place the remaining natto into the freezer to halt the fermentation process.
Make Natto from powdered bacillus natto spores
These are the packets which are sold by culturing companies for making natto. Bacillus natto is a variant of Bacillus subtilis which is found everywhere, in the soil, on plant’s roots, stokes and leaves and in most mammals gut. They are considered probiotic and necessary for maintaining health.
The benefits of using natto spore packets
Easier than other methods
Making natto this way only requires adding the powder to the cooked beans and letting it ferment in your incubation chamber. The packets are small so they don’t take up any room in the fridge or freezer and can be used immediately when taken out of the packet to inoculate a batch of beans.
Consistent results
The spores are made up of pure bacillus natto spores grown in a commercial lab which may supply commercial natto producers. This ensures that you will get consistent results as long as you follow the instructions.
Don’t need finished natto to make new
Storing finished natto for the purpose of inoculating a new batch has its drawbacks.
- It could be eaten without you knowing or by mistake
- It takes up space which could be used for something else
- The culture in the finished natto may have weakened
When starting with purified natto spores you are going to have the best chance of making consistently tasting natto.
How to make natto from powdered bacillus natto spores
Equipment:
- shallow non-reactive pan
- stockpot or some other large cooking container
- wooden spoon
- colander
- bowl large mixing bowl
Ingredients:
- two cups of soybeans
- Bacillus natto spores
Instructions:
Prepare the beans as you would for the above method.
Strain the beans in the colander and spread them out onto the shallow pan.
Cool the beans to 115˚F/46˚C. Sprinkle the spores over the beans and mix well. Wait five minutes and stir the beans again. This will give the spores a chance to hydrate a little and be mixed more thoroughly into the beans.
Cover the beans with plastic wrap and place into your incubation chamber
Let ferment for 12-24 hours depending on how strong you like your natto.
Take the container out of the incubator and package your natto into serving sized containers.
Store in the fridge for two to three days and then place them into the freezer.
Make natto from scratch
This is where most people think you have departed from reality. Making natto from scratch is a step of faith that the old traditional ways of making fermented foods are still valid today.
The first instance of natto is lost to time and we only have some stories of where it may have been discovered but the method which was used is well known and has been used to make natto for thousands of years.
Benefits of making natto from scratch
No need for any type of special starter
Starting from scratch means that you are going to use the naturally occurring bacillus subtilis found on plant stocks and leaves. Traditionally the stocks which were used were rice stocks but any type of plant stock will do.
I have seen recipes using cabbage leaves, rice stocks and oat straw. All of which will work.
Natto has a more earthy complex flavor
Natto made this way will have different flavors which are not found in the other methods. This is because at the start the bacillus subtilis bacteria do not dominate the culture on the leaves. Other species are also growing in the same environment.
When you place the beans in an environment which favors the growth of bacillus subtilis it will grow rapidly and dominate the others quickly but not instantly. This lag time gives the other bacterial strains a chance to grow and produce additional flavors in the natto. This makes it a more complex and interesting flavor.
You will have a feeling of adventure and discovery
This is a fringe activity. Wild fermentation is not a mainstream idea in this highly regulated and safety orientated society. Today with farmed food and commercialization of our food supply we are made to believe that if we make our own fermented food we are somehow poisoning ourselves.
The fermentation is done in a controlled environment to provide to encourage the growth of the wanted bacteria and inhibit the unwanted ones. Once the bacillus subtilis has dominated the culture the other bacterial strains cannot grow.
How to make natto from scratch
Equipment:
- shallow non-reactive pan
- stockpot or some other large cooking container
- wooden spoon
- colander
- bowl large mixing bowl
Ingredients:
- two cups of soybeans
- Some type of plant stocks or leaves
Instructions:
Prepare the beans as usual
Separate the leaves from the stocks
Blanch the stocks or leaves you are using in boiling water for 10 seconds
Spread a layer of stocks or leaves on the bottom of the container
Place the hot beans on top and put another layer of stocks or leaves on top
Cover with plastic wrap and place in your incubator for 12 hours
Remove the stocks or leaves from the beans and scoop into serving sized containers
Store in the fridge for two to three days. After that freeze the containers until use.
Why this method works
The bacillus subtilis bacteria is very tough. It has been studied in all sorts of extreme conditions including space. The spores are resistant to heat damage and will grow in all sorts of conditions.
By blanching the source of the spores you are destroying most of the other microorganisms which are on the source which gives the spores the upper hand in the fermentation. The warm humid environment helps to encourage their growth.
As they grow they produce a biofilm (the slimy texture on the beans) which further inhibits the growth of other bacteria in the beans. The movement of the other bacteria is slowed when they get caught in the biofilm and cannot reache their food source.
This method of fermenting natto has been used for centuries and is a valuable method to improve the health benefits of soybeans.
Can other beans be used to make natto
Let’s be clear. Natto is a fermented product made by inoculating cooked soybeans with bacillus subtilis or the strain bacillus natto. Most other beans and seeds fermented with bacillus subtilis are made in Africa using a wide variety of beans and methods.
Some of the other foods fermented with bacillus subtilis
Dawadawa
Dawadawa is traditionally made with locust beans in their natural state are inedible. The beans go through several processes and are fermented for a longer period of time before they are mashed and formed into balls to dry in the sun.
It is traditionally made by the women in Ghana as a means of support.
Sumbala
Sumbala is a fermented condiment made with nere seeds in West Africa. They are prepared much like dawadawa.
iru
Iru comes from Nigeria and is made similarly to that of dawadawa. It can be made from nere seeds soybeans or locust beans.
It is eaten fresh or dried into flat cakes for sale.
Ogiri
Ogiri is made from sesame, castor oil seed, melon seed or fluted pumpkin seed. Each type has a different flavor. The seeds are not crushed and formed into balls or cakes like the bean fermentations but rather left whole and added to dishes to enhance the flavor.
The seeds are cooked, rinsed and wrapped in banana leaves to ferment for four days. Once the fermentation process is complete they are either used immediately or dried for later use.
Bacillus subtilis can be used to ferment other beans or seeds in the same manner as that of natto. The flavor will be different. They may not have the slimy coating but they will be easier to digest and add a funky flavor.
Ways to incubate your natto
The key to making good natto is to maintain a temperature between 100˚F/40˚C for at least 12 hours. To do that you will need an incubator.
Potential ways to incubate your natto
Hot water bottles and a cooler
- Pre-heat the cooler by placing the hot water bottles in the cooler a half hour before you put the natto in.
- Ensure the hot water bottles are above the required temperature (120˚F/48˚C).
- Place a towel over the bottles to slow the heat transference and place the container holding the natto beans on top of the towel.
- Secure the lid and wait for 12 hours.
Warm oven using the pilot light
Some ovens are lighted using an incandescent light bulb. These ovens can be used as an incubator if the temperature can get above 100˚F/43˚C. You may have to use something to cordon off some of the oven to allow the small heat source to raise the temperature within the wanted range.
You can do that by using silicone mats or cookie sheets on the top rack set just below the light. Place the natto beans in the top rack and close the door.
Make sure you place a sign over the controls to prevent others from using the oven and cooking your beans rather than fermenting them.
Adjustable yogurt maker
Some yogurt makers have a temperature gauge. To use these you have to either make smaller batches or load the fermenting beans into individual containers. This is because the bacteria needs some oxygen to grow and making the depth of the beans too thick prevents their growth.
Heated incubation box
These can be bought or made depending on your preference.
They can be made from plywood, Styrofoam insulation or plastic. With a heat source on the bottom controlled by a thermostat.
Thermostats designed for terrariums are great for this just as long as they will reach the right temperature.
Hot water bottle and towels
- This is a last resort but it can also work well if you have a warm enclosed space.
- Place you hot water bottles in the center of one bath towel
- Place another on top of the water bottle
- Put the natto bean container in the center of the towels and fold them up
- You can place additional towels on top of the whole bundle to help maintain temperature.
- Close the door of the space
- This will limit the heat loss from the room and help keep the beans at the correct temperature.
- Check the temperature after six hours if it is too low add a fresh hot water bottle.