APF stands for all-purpose flour, the most common flour used in home baking. It’s a refined white flour milled from a blend of hard and soft wheat, with a moderate protein content of 8 to 12 percent. That middle-of-the-road protein level is exactly why it’s called “all-purpose”: it produces enough gluten to give structure to bread but not so much that it makes cookies or cakes tough.
What All-Purpose Flour Is Made Of
All-purpose flour comes from the endosperm of wheat kernels, the starchy interior. The bran (outer shell) and germ (nutrient-rich core) are removed during milling, which is why it’s classified as a refined flour. Manufacturers blend hard wheat, which is high in protein, with soft wheat, which is lower in protein, to land in that 8 to 12 percent sweet spot.
Most all-purpose flour sold in the U.S. is enriched, meaning vitamins and minerals lost during milling are added back in. Federal standards require each pound to contain specific amounts of thiamin, riboflavin, niacin, folic acid, and iron. Some brands also add calcium or vitamins A and D. It’s usually sold pre-sifted and ready to use straight from the bag.
Why Protein Content Matters
The protein in flour forms gluten when mixed with liquid. Gluten is a stretchy network that traps gas bubbles during baking, which is what gives bread its airy crumb and muffins their lift. More protein means more gluten, which means chewier, sturdier results. Less protein means a softer, more tender texture.
All-purpose flour sits between two extremes. Bread flour runs 12 to 14 percent protein and creates the strong, elastic dough you want for sandwich loaves and pizza crust. Cake flour drops to 5 to 8 percent protein and produces the delicate, crumbly texture of layer cakes. APF handles both jobs reasonably well, even if it’s not the absolute best choice for either one. That versatility is its entire selling point.
Bleached vs. Unbleached
You’ll find both bleached and unbleached versions on store shelves. Bleached flour has been treated with agents that whiten it and slightly alter its starch, producing softer, finer baked goods. Unbleached flour ages naturally and tends to have a slightly higher protein content, which can make results a touch denser or chewier. In most recipes, the two are interchangeable. The difference shows up most in delicate bakes like angel food cake, where bleached flour yields a lighter, whiter result.
APF in Different Countries
If you’re following a British recipe, “plain flour” is the equivalent of American all-purpose flour, but the two aren’t identical. UK plain flour typically runs 9 to 10 percent protein, while U.S. all-purpose flour trends higher at 10 to 12 percent. That gap can make a real difference. Using American APF in a British cake recipe may produce a denser result because the extra protein develops more gluten. If you notice this, reducing the flour by a tablespoon or adding a splash more liquid can help compensate.
Substituting Other Flours for APF
If a recipe calls for all-purpose flour and you only have bread flour, you can swap them one-for-one. The result will be slightly chewier, which is barely noticeable in most recipes. For yeast-based doughs like pita, adding about a teaspoon of extra water per cup of bread flour helps balance the higher protein’s thirst for liquid.
Going the other direction, you can mimic cake flour by replacing two tablespoons of each cup of APF with cornstarch, then sifting the mixture. This lowers the effective protein content and produces a more tender crumb. For whole wheat baking, substituting half the whole wheat flour with APF keeps the flavor while preventing a dense, heavy loaf.
Measuring APF Correctly
One cup of all-purpose flour weighs 120 grams, according to King Arthur Baking. That number matters because scooping flour directly from the bag can pack it down and give you significantly more than a recipe intends. The standard method is to spoon flour into your measuring cup and level it off with a straight edge. Better yet, use a kitchen scale. Consistent measuring is one of the simplest ways to get reliable results every time you bake.
Storage and Shelf Life
Stored properly, all-purpose flour keeps for six to eight months at room temperature. “Properly” means in an airtight container, in a cool, dark, dry spot. Warmth and humidity encourage insects to hatch and cause flour to clump. Flour also absorbs odors easily, so keep it away from anything with a strong smell, including soap, onions, and spices.
For longer storage, move flour to an airtight, moisture-proof container and freeze it at 0°F. Stored this way, it lasts several years. If you live in a warm climate, even short-term storage in the refrigerator helps maintain freshness. Let refrigerated or frozen flour come to room temperature before baking, since cold flour can throw off rise times in yeast recipes.