Why You Shouldn’t Skip The “Sifting” Step
If you've ever tried baking, you've no doubt come across the word "sift." Maybe you didn't understand what it meant or maybe you didn't have a sifter or sieve, so you might have skipped it altogether.
For most recipes, this may not yield catastrophic results, but for certain recipes, it can mean the difference between your recipe being a successful one or not. Most importantly, if you don't sift in your baking soda and wind up with clumps, it's going to be a nightmare because you can end up eating whole balls of baking soda which taste soapy.
What is sifting?
Sifting is when you pass dry ingredients (e.g. flour, baking soda, baking powder, or icing sugar) through a sifter or a fine sieve also called a strainer. This separates the granules from one another, "fluffing" it. It makes it easier to incorporate into batter, dough, and the like. It also makes sure that you don't get any clumps. Clumps can ruin the texture of your cooking with pockets of dryness or an unpleasant, strong flavor. (Remember the baking soda?)
The typical flour you can buy at the groceries is mostly smooth enough not to have clumps. However, the same cannot be said about icing sugar and baking soda so sifting is a required step for these ingredients.
Add this step: mixing of dry ingredients.
However, you must know that sifting does not automatically evenly mix your dry mixture. It's advisable to mix your dry ingredients together in a bowl, give it a good mix with a whisk or fork, and then sift it together.
How to get away with skipping sifting.
For some recipes, like your typical cakes and cookies, you can get away with just using a whisk or fork to fluff up your dry ingredients. When adding your baking soda, however, it's a good idea to crush any lumps in a separate bowl before sprinkling it all over the surface with your fingers to make sure there aren't any leftover lumps.
When you should NEVER skip sifting.
When you're trying to fold ingredients into a lightened mixture such as meringue, it's essential to sift the ingredients you'll add to it. This is vital for angel food cakes and other delicate sponge cakes. Sifting lets you fold the dry ingredients in easier, and also lets it incorporate better in a lighter form that won't deflate your aerated, delicate batter. It's also a big help to sift powdered sugar into your butter when making icing. The result is a lighter, more delicate frosting to use on your baked goods.
How to measure "sifted flour".
There are recipes that specifically ask for "sifted flour" before measuring and not the other way around. Though a cup of sifted and unsifted flour may look the same, packed in unsifted flour will weigh more. For these recipes, sift a heaping amount before measuring it to get a more accurate measurement.