From http://www.straightdope.com/mailbag/mcheese.html –
“Butter, now, is a bit different. Butter is typically made of chilled cream or milk, churned lightly to separate the fat from the caseous and serous parts. Those parts become buttermilk and the fat becomes butter.”
Is that so? I thought that removing butterfat from milk would just give you reduced-fat milk. I thought buttermilk was the result of some kind of souring process.
There are two different kinds of buttermilk: the stuff that’s left over when you take butterfat out of cream, and the kind that’s made from letting microorganisms act on milk. The latter is called “cultured buttermilk” and is usually easier to find at the store. Both are sour.
Reduced-fat milk is made by removing some of the cream from milk. Cream contains fat, protein, and water, not just fat.
Hmm … Okay, so how do you separate cream from milk? What is cream, exactly, anyway?
Cream is the fatty part of milk. Being lighter, it tends to float, and in the Good Old Days, it naturally floated to the top. You could skim or pour it off if you wanted, or you could shake the milk up to recombine it. In modern “homogenized” milk, the cream is kept broken into small globules within the milk that won’t float to the top, by a process I am not familiar with. No doubt someonew will enlighten us.