Wheat flour used to thicken rather than to build structure. Only about half its weight is starch; the protein and fibre making up the rest are why it thickens less efficiently than a pure starch.
What it does in a recipe: Opaque, stable thickening with a familiar cooked-flour taste that suits gravies and white sauces. Pick the swap that covers that job — the ratios below are written so you can act on them without doing any arithmetic.
Also called: Flour slurry, Beurre manie
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Thickenerscategory
Quick answer
Cornstarch
2 tbsp all-purpose flour = 1 tbsp cornstarch
All substitutes, best first
4 ways to replace flour (as thickener)
Cornstarch
Reliable
2 tbsp all-purpose flour = 1 tbsp cornstarch
Cornstarch is nearly pure starch, so it has roughly twice the thickening power by volume and needs only half as much to reach the same viscosity.
MethodSlurry it into cold water before it goes anywhere near the hot pan, and add it in the last couple of minutes of cooking.
Trade-offGlossy and translucent rather than matte and opaque, which looks wrong in a traditional white sauce or a country gravy. It also cannot be held at a simmer or reheated repeatedly without thinning.
2 tbsp flour stirred in dry = 2 tbsp flour cooked with 2 tbsp butter, then whisked into the liquid
Coating each flour particle in fat before it meets the liquid keeps the starch grains separate, so they hydrate individually instead of clumping — this is the reliable way to use flour without lumps.
MethodCook the flour and fat together for at least two minutes before adding liquid, and add the liquid gradually while whisking.
Trade-offAdds the fat's flavour and calories, and the longer you cook the roux the darker and more toasty it becomes — and the less it thickens.
Allergen checkA butter roux adds dairy. Oil or a dairy-free spread works the same way if milk is the problem; the flour itself still contains wheat either way.
Most commercial blends are built mainly from rice flour and starches, which thicken at broadly the same rate as wheat flour by volume and give the same opaque finish.
Trade-offBlends containing rice flour can feel faintly gritty in a sauce, and any blend that already includes xanthan gum will thicken more than you expect. Check the ingredient list before measuring.
Allergen checkThis is the swap for a coeliac, but blends vary — some contain soy flour, some almond or other nut flours, and some are milled in facilities that also handle wheat. Read the bag rather than trusting the front label alone.
Arrowroot is a pure starch with roughly double flour's thickening power, and unlike flour it tolerates acid well, so it suits a sauce with wine, tomato or lemon in it.
MethodAdd it off the boil at the very end; sustained heat destroys its thickening power quickly.
Trade-offGoes slippery in dairy, so it is a poor choice for a béchamel. Clear rather than opaque.
Flour needs real cooking to lose its raw taste — two to three minutes at minimum in a roux, longer in a stew. Undercooked flour is the most common reason a homemade gravy tastes pasty.
Cooking around an allergy? Diet tags here describe the ingredient itself, not any particular brand. Processed products change formulation without notice and shared production lines are common, so read the label on everything you use. A severe allergy is a medical matter — confirm with the manufacturer or your clinician rather than relying on a substitution chart.