COOKING WITH BUTTER
Butter is made by simple separation of milk fat and some water and protein from milk, or to be more precise, from cream. In principle, if we agitate a milk-derived cream for a long time we will destroy the structure of fat globules contained in it so the fats will leak out and aggregate into butter. Although you could do this at home, the process is really tedious, but fresh butter made from freshly squirted milk is so good! It can be hard to acquire the special churning equipment needed for the process though... Anyway, if you still manage to make your own butter, you will also have the opportunity to taste fresh butter milk as it is drained off the fatty mass. Even if it sounds fat, buttermilk is only 0.5% fat and contains a lot of the proteins that once have coated the fat globules. After the buttermilk has been removed, finished butter should have at least 80% fat, and the rest contains water and some protein.
Butter is very sensitive to air and light. You might have heard or seen and smelled rancid butter? This is a sign that butter has gone bad due to oxidation of its sensitive molecules. Even dark yellow dots or patches on the surface of the butter are rancid and should be removed.
How do we use butter in cooking? When we heat up butter and as it melts, we first see a lot of bubbles form and boil away. This is simply water that has reached its boiling point and evaporates due to the heat. Butter will also change color from yellow to light brown to very brown, as it is heated up. You will see that this transformation of color takes shorter time in lower heat and vice-versa. The different colors also mean different taste of butter, which suit differently in different dishes. We usually like to put melted yellow butter in pasta or on vegetables to add some flavor. Brown butter and dark butter have a more nutty aroma and can be used for fish and vegetables. These brown butter variants can also be enriched with lemon juice or vinegar (added after the butter has cooled off a little to avoid spattering!).
Butter can also be burned, especially when used for frying or sautéing. This happens often if we use high heat! For this reason, if possible, the food can be fried in oil first and then the butter can be added later at the end of cooking, or so it doesn't become burned and still adds the nice buttery taste to the dish.
If you want to make a more heat-tolerant butter you can remove the milk proteins from it (as they cause the butter to become burned). This process is called butter clarification and is simply performed by heating up butter on low heat for less than an hour, during which three distinct layers of butter components are formed. The layer of the interest is the thickest one, and it's in the middle - this is the fat, the golden yellow colored liquid. To get it, we first have to remove the foam off the surface with a spoon and then carefully pour out the clarified fat, without bringing in too much of the milk proteins that have sunk to the bottom of the pan. The fat can also be strained to further clarify it. Another trick is to refrigerate the melted butter and let the solid phases become really solid - then they are quite easy to remove and separate from the liquid butter fat. This fat can be now refrigerated and used in any dish we want - the flavor is still quite buttery and it's heat-tolerant. Because the milk solids have been removed, clarified butter is also very resistant to become rancid.