Why are hard wheat flours used for breads and yeast-raised rolls?

Hard wheat flours are preferred for breads and yeast-raised rolls because of their high protein content, which typically ranges from 12 to 15 percent. This protein is primarily composed of gluten, a mixture of water-insoluble proteins that forms an elastic network when mixed with water.123

This elastic structure is essential for the following reasons:

• Gas Retention: During the fermentation process, yeast produces carbon dioxide gas. The gluten network acts as a framework that traps this gas, allowing the dough to expand and develop a firm, spongy structure.423
• Structural Integrity: Products like bread and hard rolls require an elastic dough that can withstand significant expansion to reach a low density without collapsing.2
• Texture: The "strength" of the gluten in hard wheat flour provides the necessary elasticity to create the desired crumb structure in yeast-leavened products, whereas the "weak," flowy gluten found in soft wheat flours is better suited for products like cakes and biscuits that do not require such expansion.213