What Is Pasteurization? A Guide to Milk Treatment Types

Pasteurization is the process of heating milk to kill harmful pathogens before it becomes cheese. But not all milk is pasteurized — and the treatment it receives before cheesemaking shapes everything: flavor, safety, and in some cases, whether a cheese is even legal to sell in your country.

One of the first things we try to determine for every cheese on Fromag is how the milk was treated. Here's what each type means.

Pasteurized Milk

Pasteurization heats milk to at least 72°C (161°F) for 15 seconds, killing harmful pathogens including listeria, salmonella, and E. coli. It also deactivates the natural enzymes in raw milk that drive complex flavor development. The result is a safer, more consistent cheese — but one that trades some depth for reliability. Most commercial and supermarket cheese is pasteurized. Havarti and most mass-market Brie are classic examples.

Thermalized Milk

Thermalization is a middle ground most cheese lovers have never heard of. Milk is heated to 57–65°C (135–149°F) — warm enough to reduce bacterial load, but gentle enough to preserve more of the natural enzymes that build flavor. It's not as safe as pasteurization, and it's not as expressive as raw milk. Some producers of Gruyère and Saint-Nectaire use thermalization to balance craft and consistency.

Raw Milk

Raw milk is unheated. Every microbe, enzyme, and bacterial culture native to the animal and its environment survives — and those living cultures are what make raw milk cheese the most complex and terroir-driven of all. Comté AOP and Camembert de Normandie are made exclusively with raw milk. By EU law, several PDO cheeses must be.

In the United States, raw milk cheese aged fewer than 60 days cannot legally be sold. The FDA requires that minimum aging period as a pathogen-reduction measure.

What This Means for Pregnant Women

Raw and thermalized milk cheeses carry a higher risk of listeria and should generally be avoided during pregnancy.

The guidance differs on both sides of the Atlantic when it comes to hard, long-aged raw milk cheeses. The US CDC recommends avoiding all raw milk cheeses during pregnancy. The UK's NHS takes a more nuanced position: hard cheeses — including those made with raw milk, such as Parmigiano-Reggiano and aged Comté — are considered safe because listeria cannot survive in the low-moisture environment of a hard cheese aged 12 months or more. Soft raw milk cheeses remain high risk regardless of aging.

When in doubt, check with your healthcare provider — and check the Fromag listing, where we note milk treatment for every cheese we carry.

---

Milk Treatment at a Glance