Pasteurized cheese is cheese made from milk that has been heated to a specific temperature to kill harmful bacteria before the cheesemaking process begins. The vast majority of cheese sold in American grocery stores is pasteurized, including familiar staples like cheddar, mozzarella, cream cheese, and cottage cheese. If a cheese label doesn’t mention “raw milk,” it’s almost certainly pasteurized.
How Milk Gets Pasteurized for Cheese
Pasteurization works by applying heat for a controlled period. The two main methods used in the dairy industry differ in speed but accomplish the same goal. Vat pasteurization, the older technique, heats milk to about 155°F (69°C) and holds it there for 30 minutes. It’s still commonly used to prepare starter cultures for cheese, yogurt, and buttermilk. The faster and more widely used method, called High Temperature Short Time (HTST), pushes milk to at least 175°F (80°C) for 25 seconds or 180°F (83°C) for 15 seconds using metal plates and hot water, then cools it rapidly.
After pasteurization, the milk moves into the standard cheesemaking process: adding cultures and rennet, forming curds, draining whey, pressing, and aging. The heat treatment happens before any of these steps, so it doesn’t interfere with the chemistry that gives each cheese its texture and flavor.
What Pasteurization Kills
Raw milk can carry a range of dangerous pathogens, including Salmonella, E. coli, Listeria, Campylobacter, Brucella, and Cryptosporidium. These bacteria cause symptoms ranging from diarrhea, stomach cramps, and vomiting to severe complications like kidney failure (from hemolytic uremic syndrome), paralysis (from Guillain-Barré syndrome), and in rare cases, death. Pasteurization eliminates these organisms before they ever enter the cheese.
This matters most for soft, high-moisture cheeses like queso fresco, brie, and ricotta, where bacteria can thrive more easily than in dry, aged varieties. A hard cheese like Parmesan has less available water for bacteria to grow in, which is one reason aged cheeses have historically been considered safer even without pasteurization.
Common Pasteurized Cheeses
Most cheese you encounter in a typical supermarket is pasteurized. That includes:
- Hard and semi-hard cheeses: cheddar, Swiss, Parmesan, Asiago, Gouda
- Soft cheeses: mozzarella, ricotta, cottage cheese, cream cheese, goat cheese (chèvre)
- Blue cheeses: Gorgonzola, Roquefort, and standard blue cheese (when made with pasteurized milk)
- Processed varieties: American cheese slices, cheese spreads, string cheese, cheese curds
The cheeses most likely to be made from raw (unpasteurized) milk are artisanal or imported varieties. Traditional European cheeses like certain French brie, Camembert, and Roquefort are often made with raw milk, as are many Mexican-style fresh cheeses like queso fresco, queso blanco, and panela, particularly those sold at farmers’ markets or small producers. If you’re unsure, the label is required to state whether the milk was pasteurized or not.
The FDA’s 60-Day Rule for Raw Cheese
In the United States, cheese made from raw milk is legal, but it must be aged for a minimum of 60 days. The idea behind this rule is that the combination of time, salt, acidity, and low moisture during aging creates conditions hostile enough to kill most pathogens. This is why you can buy raw-milk cheddar or Gruyère at an American cheese counter, but you won’t find a fresh, unaged raw-milk queso fresco legally sold in stores. Any cheese aged fewer than 60 days must be made from pasteurized milk.
Does Pasteurization Change the Nutrition?
One of the most common claims about raw milk cheese is that it’s more nutritious because pasteurization destroys vitamins and beneficial enzymes. The evidence doesn’t support this in any meaningful way. Pasteurization has little effect on milk’s vitamin content. The B vitamins that milk is rich in, including riboflavin, B6, and B12, are heat-stable and survive the process well. The only vitamin significantly affected is vitamin C, which drops by roughly 5 to 17 percent depending on the method. But milk is not a significant source of vitamin C to begin with, so this loss is nutritionally irrelevant.
Key enzymes also hold up well. Plasmin, a protein-breaking enzyme important in cheese ripening, largely survives pasteurization. Lipase, a fat-digesting enzyme, is mostly inactivated by heat, but that inactivation has no impact on the nutritional value of the final product. The FDA’s position is straightforward: pasteurization kills pathogens without significantly changing milk’s nutritional quality.
Another common belief is that raw milk contains probiotic bacteria that aid digestion or reduce lactose intolerance. Raw milk does not actually contain probiotic organisms. The bacteria present in unpasteurized milk are environmental contaminants, not the carefully selected strains found in probiotic supplements or fermented foods like yogurt.
Why It Matters During Pregnancy
Pasteurized cheese is especially important for pregnant women, young children, older adults, and anyone with a weakened immune system. Listeria is the primary concern. It can cross the placenta and cause miscarriage, stillbirth, or severe infection in newborns, and pregnant women are significantly more susceptible to listeriosis than the general population.
The CDC recommends that pregnant women choose hard cheeses like cheddar, Parmesan, Swiss, and Asiago made from pasteurized milk. Soft cheeses like feta, mozzarella, cottage cheese, cream cheese, and string cheese are also fine when made with pasteurized milk. The cheeses to avoid are any type made from unpasteurized milk and fresh soft cheeses like queso fresco and queso blanco, even if made with pasteurized milk, unless they’ve been heated to 165°F or until steaming hot. The high moisture in these fresh cheeses can still support bacterial growth after production.
How to Check Your Cheese
In the U.S., the label will tell you what you need to know. Look for “made with pasteurized milk” on the ingredient list or packaging. If the cheese is made from raw milk, it will typically say “raw milk” or “unpasteurized.” Imported cheeses sometimes use less obvious language, so check carefully. At restaurants, farmers’ markets, or delis where there’s no label in front of you, asking whether the cheese is pasteurized is perfectly reasonable and something vendors hear regularly.
Shelf life varies by cheese type more than by pasteurization status. Hard pasteurized cheeses like cheddar and Parmesan last weeks to months in the refrigerator. Soft pasteurized cheeses like ricotta and cottage cheese have a shorter window, typically one to two weeks after opening. Pasteurized cheeses do benefit from lower acidity and reduced bacterial loads, which can help inhibit the growth of organisms like Listeria during storage, particularly in semi-hard varieties like Gouda.