I love to bake home-made cakes, and I always sift my dry ingredients together three times before adding them into the mixer.  I do this so that I won't have any lumps and so that I am certain the cake will be well mixed.

My mother insists that "over sifting" will make the cake dry and that she has read this in several publications.  I can't seem to find any such warning from any source.  I have never had a problem with a dry cake either.  She says I am just lucky.

So, what is the scoop on this?

--Leigh Ann

I can find no reference anywhere about cakes becoming dry from over-sifting.

It doesn't appear to make any sense, either.  Sifting serves a number of purposes. It adds air which makes the product lighter, breaks up lumps, and removes foreign particles (see Sifting Flour).  With modern milling, the chances of finding foreign particles is greatly reduced.  In baking, sifting can also help to distribute other dry ingredients like baking powder and salt evenly through the flour. 

None of these actions causes any chemical change to the ingredients being sifted, so if there was an adverse effect, it would have to come from one of the above actions, or from some side effect of sifting.  Obviously, distributing ingredients, breaking up lumps and removing unwanted material are all desirable.  In fact, the more the better, so sift on.

Can adding air to flour cause cake to become dry?  I don't believe so, but even if it could, the amount of air that is added happens mostly in the first sifting, or maybe two.  To test this, measure out a cup of flour, unsifted, straight from the bin.  Sift it, and re-measure the volume.  Sift and measure again. And again.  Do this as many times as you wish, but what you will find is that repeated sifting doesn't add more air, after the first couple of times.  Why?  Because the weight of the flour itself force air out, leaving the same result.

So finally, is there some possible side effect?  One might think of heating of the flour or mechanical changes.  The amount of heat generated by sifting would be small, plus the flour falls in a light "rain" from the sifter so it would cool off by any small amount that it was heated.

Perhaps, just maybe, sifting causes starch granules to break up, making it easier for them to absorb water.  Looking at how a sifter is constructed, though, it makes a very poor grinder so there is likely not a lot of damage to the starch granules, if any.

Now, all of this is conjecture.  Frequent readers of KitchenSavvy should know what I'm going to suggest -- make some cakes.  For some, sift only once or twice, for an equal number sift the ingredient maybe ten times and the see for yourself if there really is a difference in the dryness of the cakes.  Invite some of your taste testing friends over to help eat cake, and see if they can guess which is which.

And if any readers have a solid reference that scientifically explains why sifting would cause a cake to dry out, send a note to SpeakOut at KitchenSavvy.com, and I'll let people know.

As a final comment, since not much, if anything, is gained after the first two times you sift the ingredients, there is likely no need for the third time through.