Yeast is an essential food raw material for making steamed bread and bread. It propagates and grows in dough, decomposes sugar substances in flour, produces gas and fragrant substances, and makes steamed bread fluffy and delicious. As early as 4000 years ago, the ancient Egyptians used yeast to make bread, and our country used it to make steamed bread. It can be proved that yeast is a safe food raw material from its own structure and thousands of years' edible history.

Because consumers do not know enough about yeast, many people regard yeast as an "additive", which is a wrong concept. Yeast is a kind of microorganism, which has the characteristics of life and is rich in high-quality protein, amino acids and vitamins. It is not a chemically synthesized substance, but an organism that can be made into edible food.

Yeast is a food, not an additive. In the use standard GB2760-20 1 1 issued by China, yeast is listed in the appendix of the standard, and the food classification number of yeast is 16.04.

It is also pasta. Fermented steamed bread, bread, rolls and cakes are more nutritious than non-fermented foods such as cakes and noodles. The reason is the yeast used. Studies have proved that yeast not only changes the dough structure, makes it softer, but also greatly increases the nutritional value. Pasta fermented by edible yeast often has the following advantages:

First, yeast is rich in vitamins, minerals and enzymes. Every 1 kg of dry yeast contains protein, which is equivalent to the protein content of 5 kg of rice, 2 kg of soybean or 2.5 kg of pork. Therefore, the nutritional content of steamed bread and bread is 3-4 times higher than that of pie and noodles. Yeast is also a strong antioxidant, which can protect liver and detoxify. After fermentation, phytic acid which affects the absorption of calcium, magnesium, iron and other elements in flour can be decomposed, thus improving the absorption and utilization of these nutrients by human body.

Secondly, the energy of carbohydrates is consumed in the fermentation process, so the fermented pasta is low in calories and is the first choice for dieters. Yeast helps digestion. The calories of steamed bread and bread are lower than that of rice with the same volume, the former is only half of the latter, and the contents of fat and sugar are also lower than that of rice, so it is easier to digest steamed bread as a staple food.

As the "old-faced steamed bread" peddled by vendors, its fermented substance-"old-faced steamed bread" was found to contain a lot of mycotoxins. Experts remind consumers not to be superstitious about "old noodles", a deep-rooted traditional dough mixing method or hidden cancer risk, and call on the public to adopt modern scientific fermentation methods to make steamed bread.

Recently, technicians have taken sampling inspection in some counties and cities in Shanxi and Shandong, respectively, and tested the "old dried noodles" used by businesses using the old dried noodles production method. The results showed that all the old noodles were detected with different amounts of molds and Escherichia coli, and a considerable amount of highly carcinogenic substances-aflatoxin B 1 were also detected.

The results showed that the B 1 of mold, Escherichia coli and aflatoxin reached 2.8× 107 CFU/g, 1 10mpn/g and 5.2ug/kg, respectively. Experts pointed out that the high content of aflatoxin B 1 is directly caused by the fact that "Old Face" has many molds and secretes a lot of mycotoxins.

It is reported that the EU has strict control standards for aflatoxin B 1 in food, and its content should not exceed 2 ug/kg. The results of this mycotoxin test are amazing. Experts reminded that the market urgently needs to strengthen the supervision of "old faces".

"Old dough" is also called old leaven head, flour fat, flour head and leaven head. Put the dough in the air, let the wild yeast in the air absorb and reproduce, form a dry dough or semi-dry dough containing a certain amount of yeast, and add it to the new dough as a primer in the next fermentation to revive, reproduce and ferment the yeast.

Because the "old face" is exposed to the air, it forms a "hotbed" of pathogenic bacteria such as mold and Escherichia coli, and these bacteria also multiply and grow in large quantities, and secrete toxins, which are harmful to human health, among which aflatoxin B 1 can easily cause liver cancer.

Experts say that high-temperature cooking can kill harmful bacteria such as mold and Escherichia coli, but it cannot eliminate the toxins secreted by them. Toxins will accumulate in the human body after being absorbed by the digestive tract, and will cause cancer over time.

Experts from the Fermented Pasta Branch said: Old-faced steamed bread has a different taste, which is actually the taste of edible alkali. Because the dough is usually rancid and tastes sour by using the old noodle method, it is necessary to add edible alkali to neutralize its sour taste. So the steamed stuffed bun has a strong alkaline taste.

The vendor used the old noodles as a gimmick, saying that the taste was different. In fact, they exaggerated the alkaline taste of the old steamed bread. Over time, consumers get used to this kind of alkaline steamed bread. However, from the point of view of nutrition, the vitamins in flour, especially VB2, are greatly destroyed after adding alkali, which greatly reduces the nutritional value of steamed bread.

So, how to get safe, nutritious and healthy steamed bread? It is reported that the country promulgated the national standard of wheat flour steamed bread as early as 2007, which is a product steamed with wheat flour and water as raw materials and yeast as the main starter. In addition, according to experts, yeast is listed as a food attribute in GB2760 in China, and it is not a food additive. Its classification number in GB2760 food classification catalogue is 16.04.

Therefore, the dough fermented by yeast not only adds nutrition to steamed bread, but also decomposes phytic acid in flour and promotes the absorption of trace elements by human body. Therefore, it is best for people to eat steamed bread with yeast dough, and don't be superstitious about "old steamed bread".