Ingredients and their particular qualities affect bread’s texture, density and crust. Understanding the job of each ingredient will help you to understand the science of yeast breads.
Flours: Wheat flour contains an elastic protein called gluten, which is developed during kneading and gives bread its structure. Flours with high gluten content (hard flours), such as bread flour or all-purpose flour, yield the best results. Whole wheat and rye flours (soft flours) have less gluten; used alone, they make an extremely dense loaf. These flours are often used in combination with bread flour or all-purpose flour to achieve lighter, airier results.
Yeast: This microorganism consumes sugars in sweeteners and flours and produces carbon dioxide gas that stretches gluten strands to give breads a light, airy texture. Store yeast in the refrigerator or freezer.
Sweeteners are the food for yeast; they also tenderize, add flavor, promote browning and lengthen shelf life. White or brown sugar, molasses, honey and maple syrup are common sweeteners used in yeast breads.
Salt controls the yeast’s growth. Use the amount given in the recipe—too much salt will prevent the yeast from growing, but not enough will let the yeast grow too fast too soon, and then collapse.
Liquids: Water and milk are the primary liquids used in bread. Water gives a crunchy crust; milk gives a softer crust and a more tender crumb. Always warm liquid to the temperature stated in the recipe. Too cold, and the yeast will be slow to activate; too hot, and it will kill the yeast.
Fats (and eggs) tenderize, add moisture, carry flavor and give richness to breads.