The specific method of making natto is as follows:

1. Select and clean soybeans: remove foreign matter, insect-eaten beans, immature beans, scarred beans, etc. Wash away sand, stones and soybean stains. Please be careful not to hurt the soybeans when cleaning, and be gentle with your hands.

2. Soaking soybeans: The capacity of the container used for soaking soybeans should be more than 4 times the amount of soybeans. Once soaked, raw soybeans will expand approximately 2 times. Therefore, the amount of water released should be about 3 times the amount of soybeans. The place where soybeans are soaked should be away from direct sunlight and away from places with high temperature and humidity. 15℃ water temperature, soaking time is about 18 hours. There are 250 grams of soybeans in the container, and the amount of water added is 750 ml.

3. Cooking soybeans: Pick up the soaked soybeans with a strainer to control the moisture. When steaming and boiling soybeans, it is best to hold the soybeans between your thumb and little finger so that they can be gently crushed. You can save time if you use a pressure cooker to steam.

4. Release bacteria: Put the cooked soybeans into a sterilized container, immediately add the prepared natto bacteria (about 70-90℃), and use a sterilized spoon to stir. (If the soybeans are cooled before adding the bacterial solution, it will fail). After placing it, cover the container with a sterilized cloth and add a lid.

5. Fermentation: As the fermentation room (heating device for fermenting natto), you can use a yogurt machine to keep the temperature constant, an incubator to keep it warm, etc., but it must be kept connected to the atmosphere. In order to promote fermentation, it is best to adjust the temperature of the fermentation chamber to about 38°C in advance. The standard for mastering the fermentation temperature should be maintained at 40°C and fermented continuously for 22 to 24 hours.

6. Maturation: In order to stop the fermentation and let the aroma of natto come out, it should be placed in the refrigerator below 5℃ overnight to mature it. Fermented natto has a layer of gray-white mucus attached to the surface. When picked up with chopsticks, the silk can be pulled out to a length of more than 20 centimeters. It has a unique smell. Before eating, stir with chopsticks. The longer you stir, the greater the viscosity, the better the taste, and the higher the quality of the product.

7. Storage: It can be stored in the refrigerator for 5 days. It can be stored in the refrigerator for one year.