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Stephanie is the Head Recipe Tester of Food52.
The difference between cake flour and all-purpose flour is the proteins. Cake flour has less protein so it will develop less gluten, resulting in tender cakes. All-purpose flour has more so that it can be used for a variety of different types of recipes such as cakes, cookies, and breads. I wouldn't recommend using them interchangeably. You can always buy a small package of cake flour and store it in the freezer to keep longer.
Not an answer, but a follow up question...how long does flour keep in the freezer vs pantry? I've never tried that!
If you only have AP flour, use 1-2 tablespoons of a pure starch (corn starch, potato starch) in your cup when filling the cup with AP flour.
Kristen W. is a trusted home cook.
Rachel, I am by no means a baking expert, but due to a chronic moth problem (and a crowded fridge) I've kept AP flour in the freezer and it seems to keep there for a VERY long time.
Stored in the pantry, flour lasts about a year (though whole wheat flours will go rancid sooner than that). I've never had a bag of flour in the freezer go bad before I could use it all.