One you use for bread, one you use for all purposes.
*Snarkily brushes flour off hands.*
Wait, but wouldn’t the blanket term “all purpose” also include bread-making?
*Begrudgingly reapplies flour to hands*
At first glance, all-purpose flour and bread flour appear to be the same substance. Their pallor is similar, their consistency consistent with one another. But the two common cooking staples are compositionally unique. (While we’re on the subject of kitchen differences, what’s the deal with brown and white eggs?)
Ultimately, the differentiating factor between the two is protein content. According to Spoon University, all-purpose flour has an average protein content of 11 percent, while bread flour has an average protein content of 14 percent. (Pastry and cake flour have an average protein content of nine and seven percent, respectively.)
Now, why exactly do we use one over the other in certain recipes? What exactly does more protein mean for how each recipe turns out?
Higher protein means beefier baked goods. Protein helps with the development of gluten from the flour, and bread needs that extra heft to rise higher and structure itself more densely. Recipes which call for all-purpose flour tend to be of the lighter variety, your cakes, and muffins.
Although some recipes may survive the flour swap, some turn out just plain peculiar. For example, if you make pancakes with bread flour, the result will still be edible, but they could probably also stop a bullet. The flavors will remain the same, but the combination of tough griddling with a dense structure makes the “P” in “IHOP” stand for “pound cake.”
If protein percentages aren’t really your bag, maybe some of Grandma’s recipes are of interest. They involve flour!