Adding alkali to steamed bread will destroy the vitamin B family in the flour, so the old flour steamed bread is not as nutritious as yeast steamed bread.
In the fermentation process of making steamed bread with old flour, other harmful fungi will produce toxic substances, some of which are even carcinogenic, such as aflatoxin. After steamed bread, although fungi can be killed, the toxins produced will not disappear. Therefore, old steamed bread is not as healthy as yeast steamed bread.
In terms of taste, old steamed bread is generally steamed, otherwise it will produce sour taste again, and the second fermentation cannot be carried out, resulting in insufficient fermentation of steamed bread. Steamed steamed bread is generally compact, which is what some people call "chewy". This chewy taste is ok occasionally, and it will be difficult to swallow if you eat it a few times more, so you must eat it with soup.
After the yeast steamed bread is made, it can be fermented again. The steamed bread is soft, waxy and noisy, and tastes good. Moreover, yeast steamed bread is very easy to make the so-called "chewiness" of old-fashioned steamed bread, that is, the initiative is completely in the hands of the producer, and there is no need for secondary fermentation, while old-fashioned steamed bread can only be made solid, not soft.
To sum up, yeast steamed bread has absolute advantages in nutrition, health, taste and simple production procedures. But why are so many people touting the so-called "old-faced steamed bread"? Because habitual thinking holds that "all traditions are good". In fact, this way of thinking can lead to misunderstanding.
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Old noodles were exposed to carcinogenic toxins.
Excerpt from china health care association Net-
The "old-faced steamed bread" touted as a gimmick by vendors has recently been tested and found that its fermentation substance "old-faced steamed bread" actually contains 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 mold and Escherichia coli, and a considerable number of high carcinogens-aflatoxin B 1 were also detected. The results show that the number of molds in a sample is as high as 2.8× 10 CFU/g, and the number of molds in a sample is as high as 2.8×10 cfu/g. Experts point out that there are many "old-faced" molds that secrete a lot of mycotoxins, which is the direct reason for the high content of aflatoxin B 1. 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. Lu Feng, an expert from Fermented Noodles 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. "But from a nutritional point of view, after adding alkali, the vitamins in flour, especially VB2, are greatly destroyed, which greatly reduces the nutritional value of steamed bread." Lu Feng said. 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 Kuang Jinbao, a well-known domestic yeast expert, yeast is listed as a food attribute in GB2760, not a food additive. Its classification number in GB2760 food classification catalogue is 16.04. Kuang experts said: 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".