6 Things to Know About Milk Pasteurization

updated Oct 17, 2022
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Three glasses of cashew milk (white in color) in glassware of staggered sizes, against a blue background
Credit: Shilpa Uskokovic

Alternative milks have become the darling of the dairy case, and while these dairy-free options do have a place in our kitchens, traditional dairy milk will always play an essential role in cooking and baking recipes. Deciding which dairy milk to buy can be confusing, given the fine print on the milk carton.

What is the difference between pasteurization and ultra pasteurization? How come some milks are sold unrefrigerated on the shelf? Why does organic milk have a much longer shelf life than the conventional cartons? For the answers to these questions and more, here are the top six things to know about milk pasteurization.

Credit: Sarah Crowley

Milk Pasteurization 101

1. What is pasteurization?

Pasteurization occurs when milk is heated to 161°F for 15 seconds and is known as high temperature, short time (HTST). Pasteurization destroys organisms that can be harmful to ingest, and extends the refrigerated shelf life of milk to up to two weeks.

2. What is ultra pasteurization?

Ultra pasteurized (UP) milk, also known as ultra-high temperature (UHT) milk, is heated to 280°F for 2 seconds to destroy both illness-causing organisms and spoilage bacteria. Ultra pasteurized milk can last up to three times longer than HTST pasteurized milk.

3. Why do conventional and organic milk taste different?

It comes back to pasteurization. The flavor and nutritional value of conventional, pasteurized milk is unchanged by the pasteurization process. The higher temperature used in ultra pasteurized milk denatures some of the proteins and caramelizes some of the sugars, imparting a slightly cooked flavor and tan hue to the milk.

4. Why does organic milk have a longer shelf life?

Organic milk is not as widely produced as conventional milk, so it must travel longer distances to reach store shelves. That is why organic milk is generally ultra pasteurized, giving it a longer shelf life. 

5. What about shelf-stable milk?

Shelf-stable milk has been sterilized at 230°F to 250°F for 8 to 30 minutes to eliminate all microorganisms, and can last on the shelf, without refrigeration, for up to six months.


What Is Homogenization?

6. Can I use pasteurized milk to make cheese?

Pasteurized milk can be used for making cheeses like mozzarella, ricotta, and cream cheese at home. Avoid ultra pasteurized milk for cheesemaking, as the high heat alters the proteins so that they are not able to form the necessary curds. Because most organic milks are UHT pasteurized, make sure to check the package carefully if organic cheese is your goal.