Yeast: Baker's yeast is a single-celled plant, belonging to a fungus, and its scientific name is brewer's yeast.
Yeast shape and size vary with the type of yeast, generally round, oval, etc.
The structure of yeast is similar to other biological cells, divided into cell wall, cytoplasmic membrane, cytoplasm, nucleus and contents. Yeast is a kind of biological leavening agent, which is rich in enzymes and has amazing fermentation ability.
Like all living things, yeast is a genetic material composed of unique chromosomes, and chromosomal genes transmit genetic information. Yeast is one of the four main raw materials indispensable in bread production. In pastries, yeast is mainly used for fermented products.
The role of yeast in baked goods:
1. Expand the volume of the bread. Yeast produces carbon dioxide and alcohol during dough fermentation. The presence of a large amount of carbon dioxide can make bread loose and porous and increase its volume.
2. Improve the flavor of the product. The alcohol and organic acids produced during the fermentation of the dough. The esters are formed during baking. A variety of aromatic substances give the bread an ester fragrance.
3. Increase the nutritional value of bread. Yeast is mainly composed of protein. Dry yeast contains 30%-40% protein and a large amount of B vitamins. These nutrients capture the nutritional value of fermented food.
Fresh yeast is also called pressed yeast. Yeast strains are cultured, propagated, and separated in a medium such as molasses, and most of the water is removed to make the dry matter content reach 30%. After homogenization, they are made by pressing.
Fresh yeast has stable quality, high fermentation power, strong fermentation endurance, great stamina, good expansion when entering the oven, and a large bread volume. The product has good flavor and low price. Therefore, the use of fresh yeast should be vigorously promoted for all storage conditions, and the general amount of bread accounts for 2-3% of the flour.
To replace dry yeast with fresh yeast, just use 3 times the amount of fresh yeast. Basically, for sweet bread, it is usually 3~4% of flour, and for toast, it is 2~2.5%. When using, dissolve in 35°~40 Use it within half an hour of warm water.
General traditional dry yeast: It is made by drying fresh yeast at low temperature. Because of its low water content, it can be maintained for one year in an unopened state. Because the yeast in this state is dormant in this environment, it is necessary to wake up the yeast before kneading into the dough to awaken the vitality of the yeast. It is usually called preliminary fermentation. Before use, use about 40°C, 5,6 times of hydration, soak for 10-15 minutes, wait until it becomes a soft paste before use.
Instant dry yeast : It is a fine-grained yeast that is directly mixed with noodles. It has a strong fermenting power, and the usage amount is basically 35-40% of the fresh yeast. However, the fermentation will slow down when it encounters cold water, so it must be stirred Add in 1~2 minutes later. As for dough with a short mixing time, in winter, it is best to use 4 to 5 times the amount of yeast, and use it after boiling in warm water at 34 to 40°.
Storage Conditions
The most suitable storage for fresh yeast is refrigerated at 0-4°C. Because the yeast is in a dormant state at 0-4°C, it has only slow metabolism to maintain life. Fresh yeast can be stored for 45 days at 0-4°C.
If the storage temperature is lower than 0℃, the fresh yeast will start to freeze because the fresh yeast contains about 70% water, and the yeast will stop metabolism and gradually die, resulting in the gradual inactivation of the yeast and the slowing down of the dough. Freezing will swell the yeast cell wall after freezing the water, and the yeast will be damaged. After too much water freezes into ice, it will swell the periphery of the yeast block. After thawing, the yeast will become soft and inflexible, severely becoming a thin paste. , Yeast is completely dead and can't make dough.
If the storage temperature is higher than 5°C, the fresh yeast will begin to recover. If the storage temperature is too high, the yeast metabolism will be vigorous, aging will be accelerated, the live yeast will be reduced, and the speed of dough will slow down or even not. After the yeast dies, it becomes a nutrient-rich medium, which will grow mold and affect the taste of bread.
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