Most recipes in baking call for unsalted butter. I never really kept unsalted butter on hand, because I prefer salted butter on my toast and when I’m cooking, so I often just used the salted butter, thinking it wouldn’t make that much of a difference; I could just use less actual salt than what the recipe called for. I decided to look into it to see if there really were more benefits to using unsalted butter with baking. I learned that for the most part unsalted butter is preferred in baking because it is more fresh. Salt is used as a preservative, and it can also be used to mask odours, so if cream is not as fresh it is usually turned into salted butter, and that can overpower the natural sweet cream flavour. When you use unsalted butter, you’re getting a fresher cream, which has a better, sweeter flavour, and therefore makes your baking taste more fresh. I also learned that salt can toughen the glutens in flour, which means that baked goods would not come out as light-textured as they would with unsalted butter. Tougher gluten is good for breads, but most people prefer a dessert that is not so dense.
Obviously unsalted butter has a shorter shelf-life because it is missing that preserving salt, so it’s difficult to keep on hand for everyday use unless you’re actually using it everyday. It can be frozen, but that can affect the texture and moisture content. Butter is approximately 80% fat, 15% water, and 5% milk solids, and when it is frozen it loses some of that water, which would subsequently affect the final product, so it’s best to get it fresh whenever possible. Recipes are written with fresh ingredients in mind, and when an ingredient is altered it impacts how the other ingredients work, which is why the chemistry of baking is so interesting and precise.
When a baking recipe calls for butter, but doesn’t specify salted or unsalted, it is generally assumed that it means unsalted. If you’re like me and don’t keep unsalted butter on hand, you can easily just decrease the amount of salt that the recipe calls for. The salt content in butter varies by brand, so it’s hard to know for sure how much to decrease it, but I generally decrease the salt by 1/4 tsp per half cup of salted butter. If you’re using unsalted butter, just use the amount of salt listed in the recipe. Salted butter won’t make a bad product, just a slightly different one. You’ll get a fresher flavour, and probably lighter texture using unsalted, but butter’s main function in baking is in its fat content. And whether you use salted or unsalted, you’re always going to get a better product using butter than if you use shortening or margarine, so I strongly discourage substituting either of those for butter.
Here are a few sites where I got some of my information for this post: