Yeast is a microscopic single-celled fungus that digests sugars present in dough and produces carbon dioxide. This gas becomes trapped within the gluten strands in the flour, giving bread its characteristic airy texture. It also produces small amounts of ethyl alcohol, which contributes to the flavor and aroma of the finished bread. One of the more difficult tasks in baking homemade bread is getting the dough to rise. Proofing the yeast is one way to ensure a successful rise.
Why Proof Yeast?
Yeast is a living organism. If it is too old or is not stored in the right conditions, the yeast will die. Unfortunately, you cannot tell simply by looking at it whether your yeast is alive or dead. Proofing allows you to test the yeast before you use it in your bread dough. If the yeast does not activate during the proofing stage, the dough will not rise later in the baking process. Proofing yeast also allows you to eliminate one of the two most common problems bakers face in getting dough to rise. If you know your yeast is alive and active, and your dough still does not rise, the problem is most likely environmental. The room may be too cold or too dry. Put the dough in a warmer, more humid location and it may begin to rise.
Proofing in Milk
Bread doughs can be divided into two basic categories: lean and enriched. Lean breads, such as French and Italian loaves, contain little or no fat or other additions. Enriched loaves, such as brioche, may contain fat, dairy, eggs or sugar.
Whether you can proof your yeast in milk depends on the type of bread you are making. If you are making a lean bread, such as sourdough, you do not want the added fat or flavor of milk, because it would mask the essential characteristics of that type of bread. If you are making an enriched bread, proofing the yeast in milk will give the dough a little extra richness.
How to Proof Yeast
Use about 1/4 cup of warm, but not hot, milk or water. The temperature of the proofing liquid is crucial to the success of your bread. If the liquid is either too hot or too cold, it will kill the yeast. A temperature range of between 105 and 115 degrees Fahrenheit is ideal. Dissolve a tablespoon or two of sugar, depending on how much sugar is called for in your recipe, into the warm liquid. Sprinkle the yeast over the liquid and stir. Let this set at room temperature for about five minutes. You should see small bubbles forming on the surface of the liquid, and the mixture should have a characteristic yeasty smell.
If the proofing mixture does not develop a yeasty aroma and does not bubble at all, check that the liquid is neither too hot nor too cold. If the water or milk is close to the correct temperature, you can assume your yeast is dead. Buy a new container of yeast and try again. Yeast can be stored in an airtight container in the freezer for up to a year.
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