What is soft flour?

According to King Arthur Flour, soft flour is made from soft wheat, which contains less protein than hard wheat varieties. Protein produces gluten when agitated, so soft wheat creates a less glutinous batter or dough than other varieties.

The amount of gluten in a baked product can drastically alter its texture. Crusty breads and pizza dough require hard wheat, which contains a lot of gluten that traps carbon dioxide bubbles, resulting in a crisp and chewy texture. Soft flour is better for cakes and cookies to produce tender, crumbly baked goods. All-purpose flour has a moderate protein content, somewhere between hard and soft flours in its gluten production.