The other day, I came across a recipe calling for active dry yeast. Although I usually just convert the yeast using my yeast converter, I happened to have some active dry yeast in the fridge, so I decided to use it. Since it had been sitting in the fridge for a while, I thought I’d better test it to make sure it was still viable. It’s easy to test active dry yeast, and if you have any doubts if it is still alive, you should take a few minutes to make sure.
To test the yeast, measure 1/4 cup warm water in a one-cup measuring cup. Stir in 1/2 teaspoon sugar; stir until it dissolves. Then stir in 1/2 teaspoon active dry yeast and stir to dissolve.
If your yeast is viable, you should see activity within three to four minutes. Within 10 minutes, the mixture should double and reach the 1/2-cup mark.
As you can see, this yeast failed the test and was discarded.