In days gone by, nothing went to waste in the standard homestead, and this included the liquid leftover after churning butter. Combined with natural airborne bacteria, this liquid thickened and soured, taking on a pleasingly tangy flavour. The resulting buttermilk made an excellent addition to biscuits, pancakes, and baked goods.

Nowadays, most commercial buttermilk is made by adding a specific lactic acid bacteria culture to pasteurized sweet whole milk or, more commonly skim milk or non-fat milk. After the addition of the culture, the milk is left to ferment for 12 to 14 hours at a low temperature (optimum 20°C). It may be salted or unsalted, depending on country and producer.