Let’s geek out for a second. Gluten is essentially a network of protein strands—think of it as elastic bands. Cake flour has fewer bands, so the cake breaks apart easily. Cornstarch acts like a clean break point, preventing those bands from getting too chummy.
Fun fact: the commercial cake flour you buy is also bleached, which changes the starch’s ability to absorb liquid. Your unbleached AP flour plus cornstarch won’t be exactly the same, but it’s close enough that most home bakers—and their friends—won’t notice the difference.
This hack also works beautifully for gluten-free blends if you swap the AP for a gluten-free all-purpose and add an extra tablespoon of cornstarch. Now you’re a culinary shape-shifter.
Cultural Crumbs: A World of Texture
Think of this trick as the global currency of baking. In Japan, they use a low-protein soft flour called hakurikiko, but when it’s unavailable, home cooks often employ the cornstarch method. It’s a quiet solidarity among bakers worldwide—everyone wants a tender crumb and fewer grocery trips.
Even Martha Stewart has been known to substitute this way in a pinch. If it’s good enough for the queen of domestic perfection, it’s good enough for you on a Wednesday afternoon.
Cake Flour vs. All Purpose Flour: The Key Differences & How to Cook
