Buttermilk is a dairy drink made by addinglactic acid bacteria tomilk to produce afermented dairy drink. Traditionally, it was made from the nearly fat-free milk remaining afterchurningbutter fromcream, which wascultured with naturalbacteria prior to and during churning, giving a slight sour taste to the buttermilk. However, with the ubiquity ofrefrigeration in industrialized countries, butter in those areas is typically made from uncultured or "sweet" cream.[1] Therefore, most modern buttermilk is specifically produced by inoculating fresh,pasteurized milk, and is available in different levels of fat content.[2]
Buttermilk is consumed as a beverage and used in cooking. Drinking buttermilk remains common in warmer climates where unrefrigerated milk sours quickly, as the fermentation prevents further spoilage. In makingsoda bread, the acid in fermented buttermilk reacts with theleavening agent,sodium bicarbonate, to producecarbon dioxide. Buttermilk is used inmarination, especially forchicken andpork.
Buttermilk originated before the advent of refrigeration andhomogenization, when fresh raw milk was left to stand for a period of time to allow the cream to separate to the top. During the separation period, naturally occurring lactic acid-producing bacteria in the milk ferments it, which facilitates the butter churning process, because fat from cream with a lowerpH coalesces more readily than that of fresh cream. As this acidic environment also helps prevent potentially harmful microorganisms from growing, shelf life is increased.[3] This traditional method is susceptible to spoilage during the fermenting and churning processes, particularly under poor hygiene standards and when it is not kept cool. Refrigeration and the use of fresh milk in near-aseptically clean dairies largely eliminated these problems.
Traditional buttermilk is still common in many households acrossSouth Asia, theMiddle East, and parts of Europe, includingthe Balkans,Austria,Denmark,Finland,Germany,Ireland, theNetherlands, andPoland, but is seldom found in other Western countries. In Arab culture, buttermilk is commonly sold ice cold with other dairy products. It is consumed duringRamadan foriftar andsuhur. It is a common drink in many Indian and Nepalese homes, and may be served with roastedmaize.[4]
Commercially available cultured buttermilk is produced in the same way as yogurt, where fresh milk that has been pasteurized and homogenized, is then inoculated with a culture ofLactococcus lactis,Lactobacillus bulgaricus, orStreptococcus lactis that produces the lactic acid that sours and thickens the milk, plusLeuconostoc citrovorum to enhance the buttery quality, so as to simulate the naturally occurring bacteria in the traditional product.[4][5] The lactic acid is the product of the bacteriafermentinglactose, the primary sugar in milk. As the bacteria produce lactic acid, thepH of the milk decreases andcasein, the primary milk protein,precipitates, causing thecurdling orclabbering of milk, making cultured buttermilk thicker than plain milk.[6] While both traditional and cultured buttermilk contain lactic acid, traditional buttermilk is thinner than cultured buttermilk.[4]
Cultured buttermilk was first commercially introduced in the United States in the 1920s. It was initially consumed among immigrants. It reached peak annual sales of 517,000,000 kg (1.14×109 lb) in 1960. Consumption of buttermilk has declined since then, and annual sales in 2012 reached less than half that number.[7]However, condensed buttermilk and dried buttermilk remain common in thefood industry.[8] Liquid buttermilk is used primarily in the commercial preparation ofbaked goods andcheese.[9] Buttermilksolids are used inice cream manufacturing,[10] as well as being added topancake mixes to makebuttermilk pancakes. Home cooks can use powdered buttermilk to give baked goods a higher rise, add tang to dips, marinades, and rubs without thinning them out, and as a topping for fruits and vegetables.[11]
Traditional buttermilk has only trace levels of fat — less than 0.5 percent. Modern commercially produced buttermilk made with whole milk is 88% water, 3%protein, 3% fat, and 5%carbohydrates (see table). In a reference amount of 100 g (3.5 oz) (100 ml), whole buttermilk provides 62calories offood energy, and is a moderate source ofvitamin B12 (19% DV) andriboflavin (13% DV, table).
Acidified buttermilk or acidulated buttermilk[18] is a substitute made by adding a food-grade acid, such as distilled whitevinegar or lemon juice, to milk, using 15 millilitres (0.53 imperial fluid ounces; 0.51 US fluid ounces) of acid with 200 to 250 ml (7.0 to 8.8 imp fl oz; 6.8 to 8.5 US fl oz) of milk and letting it stand for about 10 minutes until it curdles. Any level of fat content for the milk ingredient may be used, but whole milk is usually used for baking.[19]
^Burggraaf W (3 January 2017)."Buttermilk". Safe Food Factory. Retrieved25 August 2025.
^"Buttermilk".BBC Good Food. Retrieved16 March 2024.This commercial product can be thought of as a gentler, thinner yogurt, with any buttery flavour likely added.
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