Flour is made by grinding wheat kernels into a fine powder. Standard white flour is mostly starch (around 70–75%), with 10–12% protein, 12–14% moisture, and just 1–2% fat. But the type of wheat, the part of the kernel that’s kept, and what happens after milling all shape the flour you find on store shelves.
What’s Inside a Wheat Kernel
A wheat kernel has three parts: the bran (the outer shell), the germ (the seed’s nutrient-rich core), and the endosperm (the starchy interior). White flour comes almost entirely from the endosperm. Whole wheat flour uses all three parts, which is why it’s darker, denser, and more nutritious.
The endosperm is where flour gets its two most important components: starch and protein. Starch provides structure and absorbs water during baking. The proteins are what make wheat flour unique among all flours, because when mixed with water, two specific wheat proteins combine to form gluten. One of those proteins gives dough its stretchy, flowing quality. The other provides elasticity and strength, letting bread hold its shape as it rises. No other grain produces gluten quite like wheat does, which is why wheat flour dominates baking.
How Wheat Becomes Flour
After harvest, wheat goes through a resting period called sweating before it’s ready for the mill. The grain then passes through quality control to remove stones, sticks, and stray material. Next comes tempering: moisture is added to the grain to toughen the bran so it separates cleanly from the endosperm during grinding. Once tempering is complete, the wheat berries are milled between steel rollers and then sifted (a step traditionally called bolting) to separate the fine white endosperm flour from the coarser bran and germ particles.
The more bran and germ that get sifted out, the whiter and finer the flour. Millers measure this using something called ash content, which is simply the mineral residue left when you burn a flour sample. Bran is mineral-rich, so a lower ash content means more bran was removed and the flour is more refined. It’s a quick way to gauge how “white” a flour really is.
Why Protein Content Varies by Type
Different wheat varieties contain different amounts of protein, and millers blend them to hit specific targets. That protein level is the main thing separating the types of flour on your grocery shelf.
- Cake flour: Around 10% protein. Less gluten means a softer, more tender crumb, ideal for cakes and delicate pastries.
- All-purpose flour: About 11.7% protein. A middle-ground blend designed to work reasonably well in most recipes.
- Bread flour: Roughly 12.7% protein. More gluten development gives bread its chewy texture and helps dough trap the gas produced by yeast.
Those differences sound small, but even a percentage point or two changes how dough handles and how the final product feels in your mouth. If a recipe calls for bread flour and you substitute cake flour, you’ll notice: the loaf will be flatter and softer, with less structure.
Bleaching and Enrichment
Freshly milled flour is slightly yellow and produces somewhat sticky, unpredictable doughs. Given time, flour naturally oxidizes, turning white and becoming easier to bake with. Chemical bleaching shortcuts that aging process. The FDA first approved flour bleaching in 1921, and today benzoyl peroxide is the leading bleaching agent in the United States, widely adopted since the 1980s. Chlorine gas is another common option, particularly for cake flour. Unbleached flour simply skips this step and ages naturally, which is why it has a slightly off-white color.
One bleaching agent worth knowing about is potassium bromate, which improves dough strength. It has been linked to kidney damage and cancer in animal studies, leading to bans in the European Union, Canada, and Brazil. It remains legal in the United States, though many American bakers and flour brands have voluntarily stopped using it.
Enrichment is a separate process. When white flour is milled, the bran and germ are removed, and with them go most of the vitamins and minerals. U.S. regulations require enriched flour to contain specific amounts of added nutrients per pound: 2.9 milligrams of thiamin, 1.8 milligrams of riboflavin, 24 milligrams of niacin, 0.7 milligrams of folic acid, and 20 milligrams of iron. Calcium can also be added optionally. The folic acid requirement, in particular, was introduced to help prevent neural tube defects in newborns and is considered one of the more successful public health interventions in the U.S. food supply.
Self-Rising Flour
Self-rising flour is simply all-purpose flour with leavening and salt pre-mixed in. The standard ratio is 1½ teaspoons of baking powder and ¼ teaspoon of salt per cup of flour. It’s popular in Southern U.S. baking for biscuits and quick breads because it saves a step. If a recipe calls for self-rising flour and you only have all-purpose, you can make your own by whisking in baking powder and salt at those proportions.
Flour From Sources Beyond Wheat
Not all flour comes from wheat. Dozens of plants can be dried and ground into baking-ready powders, and many of these are naturally gluten-free. Rice flour and corn flour are the most common alternatives worldwide, used in everything from tortillas to rice noodles. Almond flour (ground blanched almonds) and coconut flour are popular in low-carb and grain-free baking. Buckwheat, despite its name, is not related to wheat and contains no gluten. Chickpea flour is a staple in Indian and Mediterranean cooking.
Less familiar options include amaranth, quinoa, millet, lupin, tapioca (from cassava root), chia, and flax. Some of these, particularly chia, flax, buckwheat, and amaranth flours, are notably rich in minerals like iron, calcium, and magnesium, often exceeding what you’d find in wheat flour even before enrichment. The tradeoff is that none of them form gluten, so baking with them requires different techniques: binding agents like eggs or xanthan gum, blends of multiple flours, or recipes specifically developed for their properties.
Each alternative flour has a distinct flavor and texture. Almond flour produces dense, moist baked goods. Rice flour yields a lighter, slightly gritty crumb. Coconut flour absorbs far more liquid than wheat flour, so recipes aren’t interchangeable one-to-one. If you’re experimenting, look for recipes written for the specific flour you’re using rather than trying to swap it into a wheat-based recipe.