In the fungal family, there is a brewing "doctor" named Aspergillus, and the delicious sufu was successfully developed by it. Aspergillus hyphae have septa, belonging to multicellular mold. Its colonies have various colors. Aspergillus such as Aspergillus flavus, Monascus and Aspergillus Niger are named after the colors of the colonies. Interestingly, in the Zhou Dynasty in China, in order to dye the yellow dress-Quyi for the queen, people were specially sent to cultivate Aspergillus flavus.

Of course, people at that time didn't know the names of microorganisms, let alone the concept of colonies. The ancients just called them "five-color clothes", "yellow clothes" and so on by intuition. As early as more than 2,000 years ago, our people knew how to rely on Aspergillus to make sauce. For example, Douchi, a unique concoction in China, is also a masterpiece of Aspergillus decomposing soybeans.

The main raw materials for making soy sauce are beans and salt, and Aspergillus obtains nutrition by decomposing organic matter, so protein in beans can be decomposed into sugar and small amino acids, and these substances can be absorbed by people after being dissolved in water, so as to increase their nutrition.

However, there are some scum in the Aspergillus family, such as soybeans or peanuts that have been placed in the shade for a long time often grow "yellow hair", which is a kind of Aspergillus flavus containing toxins. Aflatoxin can not only cause poisoning and even death of poultry and livestock, but also induce human cancer, especially liver cancer. Therefore, beans or peanuts that have been moldy for a long time must not be eaten or used as feed.

Some Aspergillus can produce mycotoxins harmful to human body, such as aflatoxin B 1, which can cause cancer; Others cause mildew rot of fruits, vegetables and grain.

Now Aspergillus is an important strain in the fermentation industry and food processing industry. At present, nearly 60 species have been used, which are widely distributed in grains, air, soil and various organic items. Because Aspergillus has a unique trick to decompose complex organic substances such as protein, Aspergillus is mainly used in sauce making, wine making and vinegar making.

The ingredients of the sauce can be summarized as follows: nitrogen-containing substances include protein, polypeptide and peptide. Amino acids include tyrosine, cystine, alanine, leucine, proline, aspartic acid, lysine, arginine, histidine, glutamic acid, etc. In addition, there are putrescine, cadaverine, adenine, choline, betaine, tyrosol, tyramine and ammonia. Sugar is mainly dextrin and glucose, but also contains a small amount of pentose and pentosan.

Soybean contains about 18% fat, which basically does not change in the process of making sauce, so the fat contained in sauce is basically stored in douban. The acids contained in the sauce are formic acid, acetic acid, propionic acid, etc. Non-volatile substances include lactic acid, succinic acid and kojic acid. Other organic substances include ethanol, glycerol, vitamins, organic pigments, etc. In addition to a large amount of water and salt, inorganic substances also include sulfate, phosphate, calcium, magnesium, potassium and iron brought in with raw materials.