Store Your Yeast in the Refrigerator
Yeast should be stored in the refrigerator to prevent spoiling. Stored in this manner, yeast will keep for up to six months. To test your yeast to see if it's still good, combine 1 teaspoon sugar and 2 teaspoons yeast with ¼ cup warm water. If the mixture starts bubbling it's still good. If it doesn't it should be discarded.