White flour is one of the more difficult ingredients to measure accurately by volume, because its tiny particles not only vary in shape and size, but also have a tendency to pack. In addition, the various white flours differ in density, ranging from 100 grams per cup in cake flour to approximately 150 grams per cup in all-purpose flour. This influences the number of cups obtained from various flours of the same weight. Although there is no standard weight for a cup of flour, 1 pound of all-purpose flour averages 4 cups.
Professional bakers and chefs avoid the discrepancy in volume measurement by always weighing the flour.White flour should be sifted before being lightly spooned into a fractional measuring cup and leveled with a spatula. The cup should never be tapped or shaken down, because doing so can pack the flour particles tightly, which may result in too much flour being used. To avoid shifting and still get consistent baking results with regular white flour, one technique is to remove 2 tablespoons from each cup of un-sifted flour.
Not all flours are sifted prior to being used. Whole-grain and graham flours and meal should not be sifted, because sifting will remove the bran particles. These flours should simply be lightly stirred before being scooped into a fractional measuring cup. Pre-sifted or instant flours have already been processed into uniform particles and should not be sifted. Instant flour should not be used in baked products.
