Short answer
Wheat flour contains both gluten-forming proteins and starch, making it suitable for baking and thickening, while US cornstarch is a purified starch from corn, used mainly to thicken fillings and sauces without adding gluten or significant flavor. 1 2
Cornstarch is a purified starch, while flour contains both starch and proteins; both are used as thickeners, but only flour can form gluten.
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At a glance
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| Question | flour | cornstarch |
|---|---|---|
| Main component | Wheat proteins and starch | Purified corn starch |
| Typical use in US kitchens | Baking, thickening, structure | Thickening sauces, pie fillings |
What each thing is
Flour. Flour, in US home cooking, typically refers to wheat flour containing gluten-forming proteins and starch, used for baking and as a thickener in various recipes, including breads, cakes, and pie fillings. 1 2
Cornstarch. Cornstarch is a fine, white powder made from the starchy part of corn kernels, used in US kitchens primarily as a thickening agent for sauces, pie fillings, and other cooked mixtures. 1
Key differences
The essential difference is that flour contains both gluten-forming proteins and starch, while cornstarch is almost entirely starch. This affects their behavior in recipes, especially regarding texture and gluten development. 1 2
How to tell them apart
Flour is usually off-white and slightly granular, labeled as all-purpose or bread flour, while cornstarch is a very fine, pure white powder. However, packaging can vary and both may be sold in similar boxes or bags. 1
Where they overlap
Both flour and cornstarch are used to thicken pie fillings and sauces in US home cooking. Each absorbs liquid and helps set mixtures, though the resulting texture and appearance can differ. 1
Edge cases
Some US recipes may call for ‘flour’ as a thickener where a pure starch like cornstarch could also work, but the results—such as cloudiness or mouthfeel—will not be identical. Labels like ‘cake flour’ or ‘instant flour’ may further blur distinctions. 1
Why the distinction exists
Wheat flour includes starch along with proteins that can form gluten when hydrated and worked, giving baked goods structure. Cornstarch is processed to concentrate corn starch and lacks gluten-forming wheat proteins. Both can thicken a cooked filling, but the appearance and texture can differ with the recipe. 1 2
Common misconceptions
A common misconception is that flour and cornstarch are interchangeable in all recipes. In reality, their different compositions mean they behave differently, especially in texture, clarity, and gluten development. 1 2
Examples
A US home baker preparing apple pie might use all-purpose flour to thicken the filling, resulting in a slightly cloudy texture, or choose cornstarch for a clearer, glossier finish. Both are available in most grocery stores. 1
Sources
Sources checked October 3, 2026.
- King Arthur Baking — Fruit pie filling thickeners. Wheat flour and cornstarch as thickeners.
- King Arthur Baking — A beginner’s guide to gluten. Wheat flour proteins and gluten formation.