Buttermilk

Availability and types

What is buttermilk and where does it come from?
Buttermilk sounds like something that only comes from the kitchen. Historically that was the case: when people churned butter from cream, a thin milky liquid remained — that was the traditional buttermilk. Today the name is often used for a similar, slightly sour milk produced intentionally. In many supermarkets you won't find the “residual liquid,” but the modern variant made from milk with specific bacteria.

In which regions is buttermilk common?
Buttermilk is widespread in Europe and North America. In countries like Germany, the Netherlands, the United Kingdom and the USA you can easily find it in supermarkets. On small farms or traditional markets you sometimes still encounter the real, freshly churned variant. In some parts of the world buttermilk is less known and other types of fermented milk products are used.

Important varieties and types
Buttermilk today exists in different forms. Here are the main ones, simply explained:

In summary: buttermilk is available as the traditional residual liquid, as intentionally cultured milk, low-fat or full-fat, fresh or shelf-stable, in powder form, lactose-free and as plant-based alternatives. The cultured variant is the most common in supermarkets, while on markets and small farms you can still find the traditional form. Everyone can choose depending on whether they want it for baking, as a drink or for cooking.

Buttermilk is a fermented dairy product produced both as a traditional by-product of butter-making and intentionally by lactic acid fermentation of skimmed or partially skimmed milk. Chemically and microbiologically buttermilk differs from fresh milk mainly by an increased content of lactic acid, altered protein structures and characteristic aroma compounds such as diacetyl, which give it the slightly tangy and buttery taste.

Historically buttermilk arose as a liquid residue after skimming and churning cream to make butter. In modern food production, cultured buttermilk is mostly produced: pasteurized skimmed milk is inoculated with starter cultures, typically Lactococcus and Leuconostoc strains, and incubated at controlled temperature. During fermentation these lactic acid bacteria convert lactose to lactic acid and also produce aroma compounds (e.g. diacetyl) and sometimes exopolysaccharides that affect texture. After reaching the desired acidity the product is cooled and packaged. Homogenization and standardization of fat content are optional steps.

Fermentation lowers the pH and thereby inhibits the growth of many pathogenic organisms, which is why fermented products have a longer shelf life than fresh milk. Pasteurization before fermentation reduces the risk of pathogens; however, live cultures can remain after fermentation. Exopolysaccharides from certain cultures improve mouthfeel and viscosity without additional fat.

Buttermilk has functional properties used in baked goods, marinades and dressings: the acidity reacts with baking soda to produce carbon dioxide, which lightens doughs; the acidity denatures proteins and promotes tenderness in marinated meat; proteins and fat help emulsify sauces.

Buttermilk provides energy, protein and calcium and can contribute to a lower-calorie diet if it is skimmed. Some fermented products contain live cultures that may support the gut flora; however not every buttermilk has probiotic properties in the strict sense. People with lactose intolerance tolerate it to varying degrees: some lactose is reduced by fermentation, but buttermilk is generally not completely lactose-free. It is unsuitable for milk protein allergy.

Buttermilk should be stored refrigerated; unopened and properly cooled, shelf life is usually days to weeks depending on manufacturing and packaging. Sensory changes such as further souring, off-odors or strong phase separation indicate spoilage.

Overall buttermilk is a nutritionally interesting, technologically versatile and microbiologically stabilized component of milk processing with clearly defined chemical characteristics and established applications in gastronomy and industry.