Store opened yeast in an airtight container in the refrigerator.
To test whether yeast is still potent enough to be effective: Add 1 teaspoon sugar to 1/4 cup warm water and stir in 1 envelope (or 2 1/4 teaspoons) of yeast; let stand 10 minutes — if the yeast foams up to the 1/2 cup mark, it will still be effective.
Sources: For details about data sources used for food storage information, please
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