Butter: Salted vs Unsalted

Butter... Salted versus unsalted. Does it really matter when you're baking? In a word, YES! Butter is a key ingredient in so many baking recipes. It works in conjunction with the sugar, eggs and flour. These are all important baking ingredients that you would never consider substituting, so why should you consider making a substitution for butter? When a baking recipe calls for unsalted butter, there is a specific reason, that really does have more to do than taste. It will affect the end result of your baked good. 

Baking is Science: Butter
Butter is the preferred fat to use when baking. It has a nice flavor, unlike shortening (which has no flavor and leaves a greasy texture). Butter consists of 80% fat (European butter has 82%), the rest is milk solids and water. This fat plays an important role in baking recipes.
Generally, a baking recipe has you mix the butter and sugar together first. This action of mixing these two ingredients creates air pockets. When you add the baking soda or baking powder, this expands those air pockets and makes them larger. Adding the flour increases them even more. These air pockets are what give you a lighter, flakier dough or pastry.  These air pockets locked within the butter expand in the heat of baking and aerate the cookie or cake. Pie dough incorporate pieces of solid fat into the dough, which become flat layers of fat when the dough is rolled out. During baking, the fat melts away, leaving a flaky texture.
Butter that has been salted contains a higher water content than unsalted butter. This affects the formation of the air pockets. The salted butter will toughen the glutens in the flour, thus resulting in a tougher dough. So it is more than the flavor that is affected by the salted butter. It is also the texture.
Some people will tell you that there is a trick to reduce the salt in your recipe by 1/4 teaspoon to 1/2 cup of salted butter. But this trick will really only help with the taste, not the texture.
QUICK TIP: Higher water content, means less air pockets and tougher dough.
Butter labels to help you out at the market:
"Sweet Cream Butter" means that it was made with fresh sweet cream. This could be both salted and unsalted butter.
"Cultured Butter" is made with cultured or soured cream. This is sometimes labeled "European-style", as it is the preferred style in Europe.
"Salted Butter" is an all-purpose butter that is perfect for spreading on toast, topping on pasta or veggies. The salt has been added as a preservative, so it can last for 2-3 months. Salted butter has about 80 milligrams of sodium per tablespoon of butter. Because of the added salt, this type has a higher water content than unsalted butter.
"Unsalted Butter" has a much shorter shelf life than salted butter. It is okay to store in the freezer to preserve it longer. Just be sure to follow the recipe and allow to thaw before baking.
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