Originally, buttermilk was the lowfat liquid remaining after churning cream into butter.
It is used as a drink, in baking and confectionery.
Today Buttermilk is made by adding lactic acid-producing bacteria, usually Streptococcus lactis, to pasteurized or ultrapasteurized milk (whole, reduced-fat, lowfat, nonfat) with nonfat dry milk solids under controlled conditions. The product is heated until the desired acidity is achieved, then cooled to stop fermentation. Buttermilk flakes or liquid butter may be added to give cold milk the appearance of churned buttermilk. Salt, citric acid or sodium citrate may be added to enhance flavor.
Today, depending on the level of milk fat in the product, buttermilk may be called cultured buttermilk, cultured lowfat buttermilk or cultured skim (nonfat) buttermilk.