Natto [1] originated in ancient China [1] and was made in Qin and Han dynasties (22 BC1-220 AD). Bean products are fermented by Bacillus subtilis, which are sticky, smelly and slightly sweet. They not only retain the nutritional value of soybeans, but also are rich in vitamin K2 and vitamin K2. [ 1]
Rich in various nutrients, it can prevent intestinal diseases such as constipation and diarrhea, improve bone density, prevent osteoporosis, regulate blood pressure in two directions, dissolve old thrombotic plaque, regulate blood lipid, eliminate fatigue and comprehensively improve human immunity. The traditional method is to wrap steamed soybeans with straw, soak the straw in boiling water at 100℃ for sterilization, and keep the temperature at 40℃ for one day. Bacillus subtilis (Bacillus natto), which is common on straws, has high heat resistance because it can produce spores, and the sterilization process is not destroyed. High temperature culture speed can also inhibit other strains, so that soybean will produce sticky silk after fermentation. This sticky appearance mainly comes from glutamic acid, which is considered as natto.
It was not easy to obtain high-quality straws in the late 20th century, and most of them were sold in polystyrene foam or paper containers. Therefore, the modern production method is to mix steamed soybeans with artificially cultivated Bacillus natto, and then put them directly into a container for fermentation. Some foods other than soybeans can also be made into natto.
Modern natto made in factory
Modern natto made in factory
When making sake, if uncooked rice is accidentally contaminated by Bacillus natto, the yeast needed for brewing will be inhibited because of its fast propagation speed. Natto is not allowed to be used in sake brewing, and other fermented foods may have similar situations, so more attention should be paid to the technology.
Bacillus natto is weakly acidic, which will prevent lactic acid bacteria from producing lactic acid. Technically, natto with light odor has been developed, but due to the use of natto strains with low activity, it is easy to create room for other bacteria to breed. In addition, the natural enemy of Bacillus natto is phage virus that can parasitize bacteria. When the phage starts to act, it will reduce the activity of Bacillus natto and may cause other bacteria to start to multiply, so it is necessary to avoid eating natto beyond the shelf life.