The importance of sifting

Sifting is an important, and often forgotten, element in baking.  Historically, the act of sifting flour came about as a way of removing the lumps from the grinding stones used to mill the flour, insects and insect parts and removing the solid lumps of flour that form when flour was kept in poor, damp conditions.  However, the practise has continued into modern baking for one very good reason - it separates and aerates the flour.  This is  an important step to achieving light and fluffy cakes and muffins.  Aerating the flour allows more space between the flour molecules so the yeast have more space to grow or allows for more air for the reaction that causes baking soda/bicarbonate to create air pockets.  Whether you use yeast or bicarb, sifting clearly helps to create a lighter product.