There are many advantages, and some points to remember, when baking with buttermilk. It can add an interesting sharp and sour note to food into which it is baked. The acidity of buttermilk also can react differently with some baking ingredients, sometimes in beneficial ways. Very often, buttermilk is used as a substitute for milk, especially for those following a gluten-free diet. The unique properties and long refrigerator life of buttermilk have made it a staple ingredient in some cuisines.
When purchasing buttermilk, most of the products that are available are reduced-fat varieties. This is because they are made from skim milk, or fat-free milk. The taste of buttermilk is not reliant on the fat content; unless a recipe requires a certain amount of fat for the final product, there is no reason to choose a higher-fat variety.
Buttermilk will have an expiration date on the carton. Once opened, it can be stored in the refrigerator for up to two weeks. If the expiration date passes, it still usually can be used for another week afterward. This is primarily because of the preservative aspects of the acidity of the buttermilk.
When baking with buttermilk, it is important to be aware of the acid content. This is one of the defining features of buttermilk and it might cause it to have a different effect on certain ingredients, especially if being used as a substitution for milk. Buttermilk will react to baking soda by creating carbon dioxide. This gas will help to cause baked goods to rise more and be lighter in texture.
The acid content of buttermilk also can interact with the glutens in flour. It will relax the glutens and allow them to expand more than usual. The result is baked goods that are much softer and more tender. Replacing milk with buttermilk in a recipe can improve the texture in this way. It also can help with the browning of the sides and surface of the baked item.
If baking with buttermilk as a substitution for milk and the recipe calls for baking powder, one should reduce the amount of baking powder and add a bit of baking soda. This is because the buttermilk needs the baking soda to rise; it will not react to the baking powder in the same way.
If a recipe calls for more buttermilk than is available, it can be made quickly by adding vinegar or lemon juice to regular milk. The mixture will thicken over time. Once thick, it can be used just like buttermilk.
If there are times when baking with buttermilk that it is inconvenient to keep a supply on hand, then a product known as buttermilk powder can be purchased instead. This is a dehydrated form of buttermilk that can be reconstituted in water. Powdered buttermilk lasts a long time in the pantry, even after it has been opened.
If a recipe calls for baking soda and buttermilk, be certain the baking soda is still good. Over time, baking soda can lose its potency. This would mean that the batter would not rise while baking with buttermilk, because there would be nothing with which the buttermilk can react.