Most butter sold in the United States is not fermented. The standard sticks you find in grocery stores are “sweet cream butter,” made by churning pasteurized cream without any bacterial cultures. However, there is a category called cultured butter that is genuinely fermented, and it has a long history in European and South Asian dairy traditions. The distinction comes down to one extra step: whether live bacteria are added to the cream before churning.
Sweet Cream vs. Cultured Butter
There are two main types of butter. Sweet cream butter starts with pasteurized cream that goes straight to churning. No bacteria are introduced, and the cream stays at a near-neutral pH of about 6.0 to 6.7, similar to regular milk. This is the default butter in most American kitchens.
Cultured butter adds a fermentation step between pasteurization and churning. Specific strains of lactic acid bacteria are mixed into the cream and allowed to work before the cream is churned into butter. This fermentation drops the pH to around 4.4 to 5.0, making the butter noticeably tangier. If a label says “cultured butter” or “European-style butter,” it has been through this process.
How the Fermentation Works
The process closely mirrors what happens in cheesemaking. Bacteria such as Lactococcus lactis and Leuconostoc species are added to the cream, where they feed on lactose (milk sugar) and citric acid. As they break these down, they produce two key end products: lactic acid and a flavor compound called diacetyl.
Lactic acid is what gives cultured butter its tangy, slightly sour taste. Diacetyl is the compound responsible for what most people recognize as “buttery” flavor. It’s the same molecule that gives microwave popcorn its characteristic smell. Regular sweet cream butter contains very little diacetyl by comparison, which is why cultured butter tastes richer and more complex to many people.
The bacteria also partially break down milk proteins during fermentation, which can make cultured butter slightly easier to digest for people who are sensitive to casein. Lactose levels drop as well, since the bacteria consume it as fuel.
Why Most Butter in the U.S. Isn’t Fermented
Before refrigeration, virtually all butter was fermented by default. Cream collected over several days would naturally develop bacterial cultures before anyone got around to churning it. The tang that resulted was simply what butter tasted like.
Modern production changed that. With industrial pasteurization and refrigerated supply chains, cream could be kept fresh and churned quickly, producing a milder, more neutral-flavored product. American consumers grew accustomed to this sweeter taste, and sweet cream butter became the industry standard. In much of Europe, cultured butter remained the norm. French butter, Danish butter, and many German varieties are still made with fermented cream.
What About Ghee?
Traditional ghee, the clarified butter central to Indian cooking and Ayurvedic practice, was historically made from cultured cream. The fermentation served a practical purpose: lactic acid bacteria consumed residual milk sugar and partially broke down casein into smaller, more digestible fragments before the butter was slowly cooked down into ghee.
That slow cooking acted as a kind of second fermentation stage. Research has found that the culturing process can convert linoleic acid (an ordinary fatty acid in milk fat) into conjugated linoleic acid, or CLA, a form that has drawn interest for potential health benefits. Most commercially produced ghee today skips the culturing step, but traditionally prepared versions still use fermented cream as the starting point.
How to Tell What You’re Buying
Check the ingredients list. Sweet cream butter lists pasteurized cream (and sometimes salt). Cultured butter will say “cultured cream” or “cultured pasteurized cream.” Some brands also list “lactic acid” as an ingredient. In some cases, manufacturers add lactic acid directly to mimic the tang of true fermentation without actually culturing the cream. This produces a similar flavor but skips the live bacterial activity, so the other changes that fermentation brings, like protein breakdown and diacetyl production, may be minimal.
Brands like Président, Kerrygold (some varieties), Organic Valley Cultured Butter, and Vermont Creamery all make genuinely cultured butter that’s widely available in U.S. grocery stores. They typically cost a dollar or two more per package than standard sweet cream butter, and the flavor difference is most obvious when you eat the butter on its own, spread on bread or melted over vegetables, rather than baked into something where other flavors dominate.
Nutritional Differences
Calorie and fat content are essentially identical between sweet cream and cultured butter. Both are about 80% milkfat. The meaningful differences are subtler: cultured butter contains less lactose, slightly more diacetyl and other aroma compounds, and a lower pH. Some cultured butters contain live bacterial cultures at the time of purchase, though the count is far lower than what you’d find in yogurt or kefir. If you’re choosing cultured butter specifically for probiotic benefits, keep expectations modest. The real reasons to choose it are flavor and, for some people, easier digestibility.