Sifting flour is a process that is meant to break up any lumps in the flour, which means you can get a more accurate measurement. Sifted flour is also much lighter and airier than unsifted flour and is easier to mix into other ingredients when making batters and doughs. In the past, it was always necessary to sift in order to separate the flour from pieces of husk, seeds, and other debris, including bugs. Thankfully, todays commercial flours are refined well enough that sifting is not called for in everyday baking. However, sifting flour can still be beneficial in certain situations, such as when making angel food or sponge cakes. Sifting flour can also help distribute dry goods such as flour, cocoa powder, baking powder, and salt more evenly, which can result in a more cloud-like and moist product. If a recipe calls for sifted flour, you can use a whisk to aerate the flour before measuring it. However, if your flour has been sitting untouched for several months, it may be necessary to sift it to remove any lumps. Powdered sugar is one ingredient that should be sifted to remove lumps.