Yeast promotes bread making: sugar in flour is converted into alcohol and carbonic acid gas. This is fermentation. The generated gas swells the dough, and the generated alcohol and other by-products increase the flavor of bread. ..

There are many microorganisms on the earth. Yeast is one of them. There are many kinds of yeast. At first, they can be roughly divided into two types: chemically cultivated yeast and natural yeast.

The relationship between these two yeasts is that natural yeast is the mother of chemically cultured yeast. People extract the most suitable yeast for bread fermentation from the yeast produced by grains and fruits, and add chemicals in factories to produce a large number of chemically cultured yeasts. Compared with natural yeast, chemical yeast has the advantages of good stability and convenient use.

We often use chemical culture yeast, which can be divided into fresh yeast, traditional dry yeast and fresh dry yeast.

Fresh yeast: Yeast made by simple compression culture must be refrigerated, not frozen. Short storage time. The dosage of fresh yeast is 3 to 4 times that of ordinary dry yeast. It is said that the consumption of fresh yeast in our country varies greatly according to different brands. Please read the packing instructions carefully. What I'm talking about below is the conversion method commonly used abroad. If you want to use fresh yeast instead of dry yeast in the formula, you can use three times the amount of fresh yeast. Basically, sweet bread is generally 3-4% of flour and toast is 2-2.5%. When in use, it should be dissolved in warm water of 35-40 degrees and used within half an hour.

General dry yeast: it is a traditional granular yeast, which needs pre-fermentation. Before use, it should be used within 20 minutes after hydrating for 5 or 6 times. The dosage is less than that of fresh yeast, which is basically 50% of that of fresh yeast. Generally speaking, if it is a dry yeast that needs pre-fermentation, it is basically suitable for low-sugar dough, such as baguette, European bread, toast and so on. According to different yeast brands,

Fresh dry yeast: It is a kind of fine-grained yeast directly mixed with flour. The fermentation ability is strong, and the dosage is basically 35 ~ 40% of that of fresh yeast.

Many foreign baking books use fresh yeast. Then we don't always have fresh yeast on hand. When we want to transform dry yeast, we can transform it by the above method.

Natural yeast: Natural yeast is a wild yeast attached to air and plants. Chemical yeast is purified and contains only yeast. There are other miscellaneous bacteria such as lactic acid bacteria in natural yeast, so natural yeast is slow and unstable, but it has its own unique flavor. There are many kinds of natural yeast, including beer natural yeast, rye natural yeast, grape, pear and other fruit natural yeast. You can do it yourself. You can use rye, wheat and pears.