Pasteurization is a heat-treatment process designed to kill 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 kills 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.
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 1864.
University of Guelph. Dairy Science and Technology Department. Pasteurization. Retrieved September 2010 from http://www.foodsci.uoguelph.ca/dairyedu/pasteurization.html.