Cooking flour is made from wheat kernels that have been ground into a fine powder. The most common type, white all-purpose flour, is almost entirely composed of the starchy inner portion of the wheat kernel, with the outer layers stripped away during milling. What remains is a blend of starch, protein, and a small amount of fat and minerals, and the specific ratio of those components determines how the flour behaves in your kitchen.
Inside a Wheat Kernel
Every wheat kernel has three parts: the endosperm, the bran, and the germ. The starchy endosperm makes up 75 to 80 percent of the kernel’s weight and is the part that becomes white flour. The bran is the tough outer shell, rich in fiber and minerals. The germ is the small, nutrient-dense core that would sprout into a new plant.
White flour uses only the endosperm. Whole wheat flour keeps all three parts intact, which is why it’s darker, denser, and higher in fiber. The bran and germ contain the majority of the grain’s vitamins, minerals, and beneficial plant compounds, so removing them creates a milder, lighter flour but a less nutritious one.
Starch: The Main Component
Starch accounts for the largest share of what’s in your bag of flour. It’s made of two types of molecules: amylose and amylopectin. In standard bread wheat flour, the ratio is roughly 25 percent amylose to 75 percent amylopectin. This balance matters because amylose forms firm gels when cooled (think of a pie filling setting up), while amylopectin creates softer, more sticky textures. The interplay between the two is what gives flour its thickening power in sauces and gravies and its structure in baked goods.
Protein and Gluten Formation
Protein is the second most important component, and its percentage varies depending on the type of flour. When flour gets wet and you start mixing or kneading, two specific proteins combine to form gluten. One contributes elasticity and strength, giving bread dough its ability to stretch without tearing. The other contributes flow and extensibility, which is why cookie dough spreads in the oven rather than holding a rigid shape.
Together, these proteins make up about 80 percent of the total protein in wheat. The more protein in the flour, the more gluten it can develop, and the chewier or sturdier the final product will be. This is the single biggest difference between flour types:
- Cake flour: 7 to 9 percent protein, producing tender, delicate crumbs
- Pastry flour: 8 to 9 percent protein, slightly sturdier for pie crusts and biscuits
- All-purpose flour: 8 to 11 percent protein, a middle-ground blend
- Bread flour: 12 to 14 percent protein, ideal for chewy loaves and pizza dough
No other common grain produces gluten quite like wheat, which is why wheat flour dominates baking. Rye has some gluten-forming capacity, but much less. Rice, corn, and oat flours form none at all.
How Milling Shapes the Final Product
The way wheat is ground into flour changes what ends up in the bag. Modern commercial flour is produced through roller milling, a process that uses a series of corrugated and smooth metal rollers to crack the kernel open, separate the endosperm from the bran and germ, then progressively crush the endosperm into finer and finer particles. Sifting happens between each stage to sort particles by size.
Stone milling, the older method, grinds the whole kernel between two heavy circular stones. Because it doesn’t separate the kernel parts as cleanly, stone-milled flour tends to retain more minerals and fiber even when sieved afterward. It also produces a wider range of particle sizes, which gives bread a slightly different texture. Roller milling generates less heat during grinding, which helps with consistency and shelf life, and it’s far more efficient at high volumes. That’s why virtually all grocery store flour is roller-milled.
What Gets Added After Milling
Most white flour in the United States is both enriched and bleached, so the bag contains more than just ground wheat.
Enrichment replaces some of the nutrients lost when the bran and germ are removed. U.S. federal standards require enriched flour to contain specific amounts of thiamin, riboflavin, niacin, folic acid, and iron per pound. Calcium is optional but commonly added. This is why the ingredient list on a bag of all-purpose flour often includes a string of vitamin names after “wheat flour.”
Bleaching is a separate process that whitens the flour and alters its baking properties. Freshly milled flour has a slightly yellow tint from natural pigments called carotenoids. Left to sit for weeks, it gradually whitens and develops better baking characteristics on its own, a process historically called natural maturing. Chemical bleaching agents speed this up from weeks to hours. Benzoyl peroxide is one of the most common, acting as an oxidizer that breaks down those yellow pigments. Chlorine gas is sometimes used for cake flour specifically, because it also weakens the gluten structure and helps starch absorb more liquid, producing softer cakes. Unbleached flour skips this step and relies on time or is simply sold with its natural pale cream color.
Self-Rising Flour
Self-rising flour is all-purpose flour with two ingredients pre-mixed in: baking powder and salt. The standard ratio is 1½ teaspoons of baking powder and ¼ teaspoon of salt per cup of flour. It’s designed for quick breads, biscuits, and pancakes where you want lift without adding leavening separately. If a recipe calls for self-rising flour and you only have all-purpose, mixing those three ingredients in that ratio produces the same result.
Non-Wheat Flours
Not all cooking flour comes from wheat. Rice flour is milled from dried rice grains and is nearly pure starch with very little protein or fiber, making it useful for light batters and gluten-free baking but poor at providing structure on its own. Almond flour is simply blanched almonds ground to a fine powder, so it’s high in fat and protein but very low in carbohydrates compared to wheat. Coconut flour is made from dried, defatted coconut meat and absorbs far more liquid than wheat flour, which means recipes need significantly more eggs or moisture to compensate.
Flours made from nuts and legumes, like almond or chickpea flour, sit at the high-protein, low-carb end of the spectrum. Starches and rice-based flours sit at the opposite end, with high carbohydrate counts and minimal protein. None of these alternatives form gluten, so gluten-free baking typically blends two or more non-wheat flours together, often with added binders like xanthan gum, to approximate the structure that gluten provides naturally in wheat.