Using Cake Flour + Cornstarch Instead of All-Purpose Flour
Ratio
1:1 (sub 2 tbsp per cup with cornstarch)
Excellent — nearly identical results
Measurement Variance Note
For 1 cup references, this ingredient can vary by about 12% across brands and measuring methods (110g-140g per cup). For the most reliable substitution result, measure by weight and test a half batch first.
What changes when you swap all-purpose flour for cake flour + cornstarch
Pull two tablespoons of all-purpose from each cup and replace it with cornstarch — that 12.5% swap drops the effective protein from around 11% toward the 8% range cake flour lives in, weakening the gluten network and freeing more starch to coat sugar and fat. The crumb in a white birthday cake or chiffon comes out finer and more tender, with a softer break under the fork. It is a workable stand-in, not an exact mirror — chlorinated cake flour also absorbs liquid differently.
- Best in tender bakes — angel food, white layer cakes, hot milk sponge — where the lower protein lets the crumb stay plush instead of stretching into a chewy structure.
- Sift the cornstarch and AP together at least twice before measuring; uneven blending leaves starchy pockets that bake into pale, slack patches in the crumb.
- Skip it for cookies, biscuits, or any laminated work — you want the 10–12% protein doing the lifting there, and the cornstarch dilution leaves the dough too slack to hold shape.