How to make your Natto
❶ Wash the beans
Put the beans into a bowl and wash them well by rubbing them together. Be careful not to break the skin.
Soil and other impurities on the surface of soybeans has tons of microorganisms that have adverse effects on making Natto. Make sure to wash off all the dirt and debris.
❷ Soak the beans
Soak the washed soybeans in water which is about 4 times more the soybean weight (500g of soybeans uses 2L of water). It is better to use a big bowl since the soaking will make the soybean expand to twice it’s original volume
❸ Cook the beans
Cook the bean until it easily squashes by nipping with thumb and index finger.
The beans will have a slightly tightened texture when fermentation starts, so make sure to boil it to tender at this stage.
It takes approx. 30mins for a pressure cooker to cook. (The result may vary depending on a cooker. Please refer to the instruction manual for the exact cooking time)
It takes 3 to 4 hours to cook using an ordinary saucepan
❹ Dissolve Natto starter into water and make “Natto solution”
Pour 10ml of sterilised water (pre-boiled and then cooled water) in a cup and dissolve 0.1g of Natto starter (one fifth of small teaspoon) in it.
Use this Natto solution to ferment the beans.
It is easier to succeed with more Natto solution. For the first timer, using greater amount than this recipe is recommended. Use up to 1g per 10ml of water.
❺ Pour the Natto solution over the beans
Drain you cooked soybean well and allow to cool 40 degrees. Using a thermometer is recommend.
Then pour the Natto solution and mix thoroughly.
6 Put the soybean mixture in a container
Quickly put the soybean mixture in a container such as Tupperware.
Using a yogurt maker
Transfer the inoculated soybeans to the container which is attached with the yogurt maker. Fermentation needs oxygen. So don’t use the lid or keep vent open.
❼ Keeping it warm for fermentation
Keep the soybean mixture in a warmer for 24 hours to ferment. The best temperature for Natto solution to ferment is 40 to 45 degrees.
It comes in handy if you have a yogurt maker. Keep the temperature steady at 40 degrees and set the timer for 24 hours when using a yogurt maker.
Fermentation requires oxygen. Remember to keep the vent open
❽ Transfer the fermented beans to refrigerator to mature
Transfer the fermented beans to a refrigerator.
By resting the beans in a fridge for a day, amino acid composition of soy protein will enrich the flavour of Natto.
Natto is now ready to be served.
If you are not planning to eat immediately, store in refrigerated for up to five day or keep frozen for up to 2 years.