Before you can bake with yeast, you have test it first to make sure it's still alive and well. Here's how to do it.
proofing yeast in a measuring cup
| Credit: Meredith

What is Yeast?

Yeast is a leavener that you add to dough to make it rise as it bakes. No matter what form your yeast comes in — active dry yeast, instant (or rapid-rise), or fresh yeast — it needs to multiply and grow in a sympathetic environment. The correct environment includes moisture, food (in the form of sugar or starch), and a warm, nurturing temperature.

What is Proofing?

Before you bake with active dry yeast or fresh yeast, you must test it first to make sure the yeast is alive. The act of testing to see if yeast is alive is called proofing. (Proofing rapid rise or instant yeast is not recommended.)

If the yeast is dead, no amount of environment will help it become a productive leavening agent.

How to Proof Yeast

  1. We used 1/2 cup water, 1 tablespoon white sugar, and one package of yeast for this test. You can use this method to test active dry yeast or fresh yeast. Fresh yeast is more perishable and should definitely be tested if you haven't used ti in a while.
  2. Heat the water to approximately 100 degrees F (40 degrees C). We recommend testing the water temperature using a thermometer. Once you've done this a few times, you'll get a natural feel for how warm the water should be without being too hot to kill the yeast culture.
  3. Whisk the sugar into the water to help it dissolve. Why sugar? Yeast eats various sugars and excretes alcohol and carbon dioxide. Alcohol and carbon dioxide are what the pockets in bread are filled with as bread bakes. In other words, sugar makes a feast for the yeast.
  4. Once the sugar has been evenly distributed throughout the water, add the yeast. Stir gently and let it sit.
  5. After 5 or 10 minutes, the yeast should begin to form a creamy foam on the surface of the water. That foam means the yeast is alive. You can now proceed to combine the yeast mixture with the flour and other dry ingredients in your recipe. If there is no foam, the yeast is dead and you should start over with a new packet of yeast.

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