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.

A pasteurization method known as “High Temperature Short Time” is designed to kill 99.999% of the number of the micro-organisms in fluid milk. (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.

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.

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 procedure of treating milk with heat that doesn't quite qualify as pasteurization because it doesn't reach the temperature required to kill Listeria . The milk is heated to between 40 and 72 C (104 and 162 F .) It reduces bacterial...

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...