Most of us, when we think of Oxygen, think of its life giving properties that our bodies rely on continuously. It makes up 20% of the air we breathe where it is second only to Nitrogen. Now a smaller group of you (those who may have actually enjoyed their chemistry courses) may have gone somewhere completely different when I said Oxygen. That’s because you know that these same elements that make up our air have the potential to react with the things they come into contact with (which because its air, is quite a bit of stuff).
When thinking of these reactions, metals often comes to mind. Some of these reactions are positive, like the green patina that forms on copper when it comes into contact with oxygen. This coating actually protects the copper underneath from further damage. One well know example of this is the Statue of Liberty and its green hue. Other reactions, however, can be detrimental. One of these that we are very familiar with is rust. Rust is the result of iron reacting with oxygen to form an iron oxide which will eventually completely replace the iron.
Now another form of rust (or at least some call it that) is the brown discoloration that occurs if you leave your apple slices out too long. This also is caused by oxidation. But one reaction that I had never thought of before was the reaction between oxygen and butter. Oxidized butter, what is that? Well you know that discolored skin that forms on it if you leave it out on the counter for too long (or the stuff that makes your butter takes like feet)? Well that’s oxidation as well. So contact with air is bad for your butter. But there are two other things which accelerate the oxidization process as well: heat and light. So obviously keeping butter in a cool dark place (i.e., the refrigerator or freezer) will also retard the process significantly.
But for those of us who like to actually use our butter as a spread, keeping the butter at room temperature is ideal. However in order to keep your butter fresh at room temperature, you need to do your best to remove as much of the other two elements as possible. So a clear glass butter dish may not be your friend here. My mother in law recently introduced us to something called a butter bell which is designed to solve this problem. The history of this device seems somewhat unclear but the principle is simple. The butter is placed inside a cup which is then inverted and submerged in a larger cup containing water. The water forms a seal preventing additional airflow into the chamber containing the butter. Since these are typically ceramic, they provide the additional benefit of blocking out all light. Ours seems to be working pretty well. Just keep it out of the sun or you will end up fishing for your butter instead of spreading it.