Bacteria, Viruses, and Protists

Bacteria Basics

What is pasteurization?

The term pasteurization is familiar to everyone—especially those who drink milk or soy milk products. In general, it is the process of heating liquids, such as milk, to destroy microorganisms that can cause spoilage and disease. This process was developed by French chemist Louis Pasteur (1822–1895) as a method to control the microbial contamination of wine. Pasteurization is commonly used to kill pathogenic bacteria, such as Mycobacterium, Brucella, Salmonella, and Streptococcus—all common to milk and other beverages.

Three methods exist for pasteurizing milk. In the first method, low-temperature holding (LTH), the milk is heated to 145°F (62.8°C) for thirty minutes. In the second method, high-temperature short-time (HTST), the milk is exposed to a temperature of 161°F (71.7°C) for fifteen seconds—a technique also known as flash pasteurization. The most recent method allows milk to be treated at 286°F (141°C) for two seconds; this approach is referred to as ultrahigh temperature (UHT) processing. Shorter-term processing results in improved flavor and extended product shelf life—but to some people it changes the taste of the milk.


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