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Distinguishing Between Cake Flour and All Purpose Flour

A few weeks ago I stored cake flour and all purpose flour in (separate) containers in the fridge and forgot to label them. Anyone have any idea how to distinguish between them now?

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  1. They have different weights for volume I think.

    2 Replies
    1. re: magiesmom

      That's probably the best way to figure it out.

      Cake flour also tends to be softer more like cornstarch

      1. re: magiesmom

        Yes, one cup of AP flour is about 4 1/2 oz; cake flour about 3 1/2-4. Just make sure they're equally fluffed and measured.

      2. Are they equal volume? I buy my AP in 5lb sacks but cake flour comes in very small boxes. Other than that I wouldn't have a clue how to differentiate them.

        1. Call the King Arthur Flour hotline, or e-mail them. Their order line is 800-827-6836. I'm sure they can transfer your call to the correct person.

          2 Replies
          1. re: greygarious

            I tried calling their baking hotline just now (a different number I got from their website) and the answer was that the weights per volume are the same (which contradicts what I find elsewhere, for some reason) and that there's basically no way to tell, but also for cake it doesn't really matter, so I'm not super concerned.

            1. re: lamb_da_calculus

              Funny that their answer differs from their website. It says here that their AP is 4 1/2 and their cake is 4.


              Is your AP bleached or unbleached? If it's unbleached, cake flour is bleached and looks more refined/white/lighter. I usually buy unbleached ap but it's hard to find unbleached cake flour so mine is bleached.

              If you're making cake, ap will make for a firmer texture but it will work fine.

          2. Is all-purpose flour slightly yellowish, while cake flour is whiter? (In sunlight, not artificial light.)
            I don't know if this is true, I'm just asking.

            1. Try squeezing a sample of each in to a lump, cake flour will form a dense lump that will resist falling apart while a lump of AP flour will fall apart much more easily.

              1. You can tell by feel though it is a subtle differance.
                Cake Flour feels softer and finer than A.P. which is less powdery and a bit grainy in comparison.

                1. I think that cake flour will feel like it's been sifted, if you touch it.

                  However, if that's not working, you could purchase another box or sack of either, then compare the new purchase with the 2 unlabelled and see if one matches.

                  1. Color! (I just compared my King Arthur AP to Swans Down.) If your AP flour is unbleached and you're using real cake flour (which by definition is, and is snowy white), the color difference is quite apparent. I imagine that since most AP flour also contains some barley flour, that makes the comparison easier, too. They look somewhat different in texture as well but color is an easy and accurate way to check. If you're using King Arthur Cake Flour Blend, though, I'm not sure a color check will work because it's not real cake flour.