Pasteurization

Pasteurization is a heat-treatment process designed to inactivate bacteria.

It is not as thorough as sterilization: it is not intended to kill all micro-organisms, just to greatly reduce the number of ones that could cause illness and disease. It also extends the refrigerated shelf life of products.

Pasteurization is a function of both temperature and time.

“Vat pasteurization” brings the milk to 63ºC (145ºF) for 30 minutes. ^[1]Pasteurization. International Dairy Foods Association. Accessed September 2022 at https://www.idfa.org/pasteurization .

A pasteurization method known as “High Temperature Short Time” (72 °C × 15 seconds) is designed to kill 99.999% of the number of the micro-organisms in fluid milk in 15 seconds. (Note it doesn’t remove the microbes; it just inactivates them.)

Pasteurization processes are usually legally defined in country or in a jurisdiction, by laws governing food.

There are two main pasteurization techniques:

• High Temperature/Short Time (HTST)
• Ultra High Temperature (UHT)

There is also a third process, Thermalization, which many government health departments don’t recognize as pasteurization for legal purposes.

Pasteurization is typically applied to dairy, fruit juices, and (in North America) apple cider. Since September 2007, all almonds produced in California have to be pasteurized.

There is now also a technique for pasteurizing whole, shell eggs. See the entry on Pasteurized Eggs.

Unpasteurized milk is referred to as raw milk.

See also: Listeria, Anniversary of First Pasteurisation Test

History Notes

The pasteurization process was discovered by French scientist Louis Pasteur. At the time, he was investigating why wine and beer spoiled. He was working with Claude Bernard. Their first test was on 20 April 1862.

Further reading

Pasteurization time / temperature tables.

Sources

University of Guelph. Dairy Science and Technology Department. Pasteurization. Retrieved September 2010 from http://www.foodsci.uoguelph.ca/dairyedu/pasteurization.html.

Related techniques

HTST Pasteurization

HTST pasteurization means that the item being pasteurized is exposed to a "High Temperature" for a "Short Time"; thus, the "HTST" moniker. Generally, the item is exposed to heat of 160 to 165 F (71 to 74 C) for 10 to 20 seconds. HTST will give...

Micro-Filtered Milk

Micro-Filtered Milk is milk that has been treated to a very fine filtration process. It removes more bacteria than pasteurization. Producers say it removes 99.5% of bacteria present in milk. It also gives milk a longer shelf life, of up to 30 to 45...

Thermalize

Thermalization is a harm-reduction procedure of heat treating milk to reduce bacterial loads. It leaves alive some enzymes prized by some cheesemakers, but because it does not inactivate key pathogens of concern, it is not regarded as being as safe as...

UHT Pasteurization

UHT stands for Ultra High Temperature. It is a non-chemical heat process that extends the shelf-life of milk up to 55 days. The milk is heated to about 137 C (280 F) for a minimum of 2 seconds to kill all traces of bacteria in the milk. The...