Yes, cultured milk sold commercially in the United States is pasteurized. Federal regulations require that the milk be pasteurized or ultra-pasteurized before live bacterial cultures are added. This means the heat treatment happens first, and fermentation happens second, so the beneficial bacteria in the final product are never exposed to pasteurization temperatures.
How the Process Works
The sequence matters here, and it’s the key to understanding this topic. During manufacturing, raw milk is first heated to at least 72°C (about 162°F) for 15 seconds in what’s called high-temperature short-time pasteurization. This kills harmful bacteria like Salmonella, E. coli, Listeria, and Campylobacter. The milk is then cooled down before bacterial starter cultures are introduced.
Once those cultures are added, fermentation begins. This is the stage where the milk thickens, develops its tangy flavor, and becomes what we recognize as cultured milk. The bacteria convert lactose into lactic acid, which gives the product its characteristic taste and texture. The final product must contain at least 3.25% milkfat, at least 8.25% milk solids not fat, and a titratable acidity of at least 0.5% lactic acid, per the FDA’s standard of identity under 21 CFR 131.112.
Yogurt production uses an even more intense heat treatment than regular milk pasteurization. Yogurt milk is typically heated to 85°C for 30 minutes or 90°C for 1 to 2 minutes. This higher temperature isn’t just about safety; it changes the protein structure of the milk in ways that help the yogurt set into a thicker, more stable gel.
Live Cultures Survive Because of the Timing
A common source of confusion is how cultured milk can be both pasteurized and contain live bacteria. The answer is simply that pasteurization comes before the cultures go in. The bacteria are added to already-cooled, already-pasteurized milk, so they’re never subjected to the heat that would kill them. By the time you buy the product, those cultures are alive and active in the container.
Some products, however, are heat-treated again after fermentation. These do not contain live cultures, and the FDA requires them to say so on the label. If yogurt has been pasteurized or sterilized after fermentation, it must be clearly labeled with a phrase like “pasteurized after fermentation” or “does not contain live and active cultures.” So if live cultures matter to you, check for labeling that says “contains live and active cultures.” The FDA now sets a minimum culture count for yogurt that carries this claim.
Other Cultured Dairy Products
The same basic principle applies across cultured dairy products. Buttermilk, kefir, and yogurt all start with pasteurized milk that is then fermented with specific bacterial (and in kefir’s case, yeast) cultures. The milk is pasteurized and cooled before kefir grains or starter cultures are introduced. Buttermilk follows the same pattern: pasteurized milk, then bacterial culture addition, then fermentation.
Each product uses different combinations of microorganisms that produce distinct flavors and textures, but the underlying food safety approach is the same. Heat first, culture second.
What About Raw Cultured Milk?
Raw (unpasteurized) cultured milk does exist, but it occupies a legal gray area. The FDA banned the interstate sale of raw milk in 1987, and 20 states explicitly prohibit intrastate raw milk sales as well. The remaining 30 states allow raw milk sales in some form, which means raw cultured products like raw milk kefir or raw milk yogurt can be found at some farms and specialty retailers depending on where you live.
The safety record of raw milk is concerning. Since 1987, there have been 143 reported outbreaks of illness linked to raw milk and raw milk products, including cases of kidney failure, miscarriages, stillbirths, and deaths. The elderly, children, pregnant women, and people with weakened immune systems face the highest risk. Some advocates claim raw milk offers nutritional advantages, but the evidence doesn’t support this.
Pasteurization and Nutrition
One reason people search this question is concern that pasteurization strips away nutrients. Research consistently shows this isn’t the case in any meaningful way. The mineral content and bioavailability of calcium, zinc, and selenium in milk are unaffected by pasteurization. Fat-soluble vitamins (A, D, E, and K) and most water-soluble B vitamins remain largely intact. Pasteurization has little effect on overall vitamin levels.
The allergenicity of milk proteins also doesn’t change with pasteurization. Both animal and human clinical studies have found no difference in allergic sensitization between raw and pasteurized milk. Pasteurization causes only limited changes to whey proteins and minimal changes to casein structure, which explains why the body’s immune response to the proteins stays the same. The milk’s natural antimicrobial components also aren’t completely inactivated by pasteurization, contrary to what some raw milk proponents claim.
In short, commercially sold cultured milk gives you the safety benefits of pasteurization, the nutritional profile of whole milk, and live beneficial bacteria, all in the same product.