The more protein a flour contains, the higher its gluten content, as the protein helps gluten develop during the bread-making process. Using a flour with less protein, such as all-purpose flour, in place of a flour with higher protein, such as bread flour, affects the texture and quality of your baked good.
High-gluten bread flour helps breads develop structure and texture. It contains between 14 to 16 percent gluten, while all-purpose flour has only 10 to 12 percent. The exact gluten content will change depending on the brand and the country you are in.
The high-protein content of bread flour helps breads develop stronger structure, giving them a pleasing chew, and helps yeast breads rise faster and higher. The more protein -- and thus more gluten -- there is in the flour, the denser and chewier the final product.
Bread flour, like all-purpose flour, can be bleached or unbleached, and is used only for breads, such as pizza crusts and bagels. Breads made with all-purpose flour may be crumbly and less elastic than those made with bread flour.