Dry yeast, most of the time our impression of it stays in 'a kind of fermentation powder', and forget that it is also a kind of microorganism, a kind of fungus.
Since it's a fungus, it has life. It's just that the dry yeast we usually contact is the product after compression and drying. The yeast has been 'dormant'. When making bread, steamed bread and other hair food, the dry yeast will 'wake up' and start to grow and reproduce, so that the dough will rise.
Similarly, since it is life, there will be death. If the dry yeast is not preserved properly or the shelf life is exceeded, the yeast will die in large quantities and no longer have the ability to ferment. Using this kind of yeast to make bread, of course, will not have a good effect -- not only wasted energy and time, watching how hard kneaded dough can not rise, but also affect your mood.
1. After the yeast is dissolved in warm water, wait for 5-10 minutes. If the active yeast is good, the surface will float quickly. If there are no bubbles or bubbles, the activity of yeast is not good enough to be used again.
2. Add 1 / 2 teaspoon sugar into warm water to serve as the nutrition of yeast, so that yeast can grow rapidly and be easy to observe.
3. If the dry yeast you buy is in large package, it can be stored at room temperature before opening. After opening, please put it into a sealed bottle and refrigerate it in the refrigerator (5 ℃), the sooner you use it, the better. It is recommended to buy small packages of yeast for home use, so as not to lose activity due to long-term use.
4. It is not necessarily the reason why the dough can not grow. The temperature, oil content and salt content of the dough will affect the fermentation speed and effect. But yeast failure is the most common problem. Therefore, to test whether yeast has activity, we can avoid making the simplest mistake, let us not fail at the beginning.