Many people labor under the misconception that buttermilk is basically a buttery, high-fat milk. This couldn't be farther from the truth. Not only is there no butter, per se, in buttermilk, but it's actually lower in fat than sweet milk. The "butter" in the word buttermilk is not a reference to its butteriness, but rather an explanation of where this versatile fermented beverage comes from.
Origins of Buttermilk
Old-fashioned homemade buttermilk is the slightly sour, residual liquid which remains after butter is churned. It is usually flecked with tiny spots of sweet, creamy butter that did not quite make it to the top to be skimmed. The liquid is left to ferment overnight, which converts the milk sugars into lactic acid. The lactic acid is what makes buttermilk so desirable for baking, and what gives it a tangy flavor.
The Flavor of Buttermilk
The flavor of buttermilk is reminiscent of yogurt 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.
Commercially Made Buttermilk
Nowadays, most buttermilk is made by an industrial process that has little to do with making butter. First, a bacteria culture is added to pasteurized sweet whole milk or, more commonly, skim or non-fat milk. Flecks of butter may or may not be added as well. After the addition of the bacteria, the milk is left to ferment for 12 to 14 hours at a low temperature (optimum 69 F). Salt, stabilizers, and sugar may be added to the buttermilk as well. Processed this way, it is usually labeled cultured buttermilk.
Uses of Buttermilk
Buttermilk was prized by older generations for its tangy flavor and remarkable properties in baking. When paired with baking soda, as it is in recipes such as buttermilk pancakes and buttermilk biscuits, the buttermilk's lactic acid reacts vigorously, creating a great rise and exceptional crumb. In addition, the lactic acid can be used to tenderize meats, as it is often called upon to do in fried chicken recipes.
Buttermilk and Digestive Health
Buttermilk made the old-fashioned way is a rich source of probiotics. Like yogurt or kefir, buttermilk that contains active cultures can introduce or reintroduce gut flora that may have been lost due to antibiotic regimens. These bacteria enhance digestion, aid in nutrition and combat digestive issues from flatulence to Crohn's disease. Those suffering from indigestion or reflux may find that the richness of buttermilk soothes an inflamed esophagus. Be sure that the buttermilk contains live cultures; pasteurized buttermilk will have killed off the bacteria after they produced all that tangy acid.