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What is the difference between the three methods of chemical leavening, old dough fermentation and yeast fermentation?

Chemical leavening refers to the use of chemical leavening agents (commonly known as "baking powder") in flour to expand the dough. The chemical leavening agents produce chemical reactions in the environment of water and high temperature and release gas, which makes the dough leaven.This method is characterized by a quick start.However, the formula of chemical leavening agent usually contains aluminum potassium sulfate or aluminum ammonia sulfate (commonly known as "alum"), which is easy to lead to aluminum residue in the flour, which is harmful to human health. Therefore, the state has issued relevant regulations to restrict the use of aluminum leavening agent in flour food.At present, there are "aluminum-free" leavening agents on the market, which can be used for dough leavening. However, as a chemical method of "instant leavening", they are not recommended by nutritionists.

The leavening agent in the fermentation of old noodles (also called leaven head in some places, dough head or flour fertilizer) is mainly yeast, but this kind of yeast is the wild yeast in the air.This method is the most original method, which is characterized by the inclusion of other bacteria, complex flavor.However, exposure to the environment is also easy to make the old face breeding adverse to human health microorganisms (such as mold, e. coli, etc.), so this method is not sanitary, not healthy;In addition, because the yeast in the old noodle is not pure and the fermentation ability is weak, it often needs a long time to ferment, and the dough cannot be fully fermented, which will easily lead to the sourness of the dough. People often add alkali to adjust the sour taste, which will greatly damage the nutritional value of the dough.At present, this method has been gradually eliminated.

Yeast fermentation is a method of fermenting dough using commercial yeasts specially developed for production.This kind of yeast has high activity and strong fermenting ability. It can quickly absorb the saccharide in the flour and convert it into gas and various flavoring substances.Compared with the old dough method, the yeast fermented dough can be made into finished product in 0.5-1 hour at the soonest, which is convenient, healthy, high production efficiency, time-saving and labor-saving.Compared with chemical leavening agent method, yeast fermentation has advantages of health, nutrition and safety.

Yeast fermentation is now highly respected, not only because it can replace chemical leavening agent, become the best way to eliminate the "aluminum harm" of the flour, but also because yeast in the fermentation process has greatly improved the nutritional value of the flour.

First, yeast fermentation can increase the protein content of pasta by 8% ~ 10%, the content of B vitamins by more than 30%, and the content of calcium, iron, zinc, potassium, magnesium and other minerals by more than 20%.At the same time, yeast fermentation can degrade phytic acid in flour and improve the absorption and utilization of calcium, iron, zinc and other minerals.Yeast also contains rich lysine, can make up for the lack of lysine in flour, improve the nutritional value of flour.

Secondly, yeast contains a variety of active ingredients, such as phytase, amylase and other ingredients in the flour can be decomposed into the human body is easy to absorb amino acids, small molecules of sugar, etc.