Staples - about Yeast
Yeast - is a form of leavening that comes in dry, granular form, which can be stored simply in the cupboard, or in compressed cakes, which are more perishable and should be kept in the refrigerator or freezer. Both are equally satisfactory
Yeast is what releases the gases that make the dough rise, thus lightening the bread. It is really a tiny living fungus that thrives on sweetness, warmth, and moisture. Yeast should not be rushed in its activity; given sufficient time it will not only make dough rise but will work on the gluten in the flour to develop good flavor and texture.
Yeast is usually stirred into a small amount of warm liquid and allowed to stand for about 5 minutes to dissolve. If you have any doubt about freshness, "Proof" the yeast by dissolving it in 1/4 cup of warm water and adding a teaspoon sugar and 2 tablespoons flour, if the yeast is active it will be spurred on by the sugar to feed on the flour, and within 10 minutes you will see it begin to expand and foam.
The temperature of the liquid in which yeast is dissolved is important.
Yeast will not grow in a solution that is too cold, while one that is too hot will kill it.
Compressed yeast should dissolve in lukewarm water or milk at about 100-105F,
Dry yeast will tolerate somewhat warmer temperatures about 100-115F
test the water with your fingers or on your wrist and you will soon have a good feel for it.
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