Bread flour is milled from hard wheat varieties selected for high protein content, typically 12 to 14 percent, which forms strong gluten networks when mixed with water. This gluten traps carbon dioxide produced by yeast fermentation, allowing dough to rise and giving bread its characteristic open crumb and chewy texture. It is available as white, wholemeal, and specialty versions, and differs from soft cake or pastry flours that produce tender, crumbly results. Bakers adjust hydration and kneading to develop the gluten fully. Strong flour is the foundation of yeast-leavened breads from sandwich loaves to artisan sourdough.