Did You Know: There is No Butter in Buttermilk
You might be surprised to learn there is no butter, per se, in buttermilk, and it is lower in fat than sweet milk.
Old-fashioned homemade buttermilk is the slightly sour, residual liquid which remains after butter is churned, ie. milk from the butter or buttermilk. It was usually flecked with tiny spots of sweet, creamy butter that did not quite make it to the top to be skimmed.
The flavor of buttermilk is reminiscent of yougurt and most people prefer it well-chilled. You will find it to be slightly thicker in texture than regular milk but not as heavy as cream.
It takes 1 gallon of milk to yield 1/2 pint of true buttermilk.
Nowadays, most commercial buttermilk is made by adding a lactic acid bacteria culture to pasteurized sweet whole milk or, more commonly skim milk or non-fat milk, and it may or may not have added butter flecks.
After the addition of the culture, the milk is left to ferment for 12 to 14 hours at a low temperature (optimum 69 degrees F.). It is usually labeled cultured buttermilk and may be salted or unsalted. Most commercial varieties are salted, so check the label if you are on a sodium-restricted diet.