Why is milk pasteurized?
Pasteurization is a heating process used to make foods and beverages, including milk, safe for consumption. First suggested for milk in 1886, it was widely adopted in the early 20th century to combat diseases once commonly carried in raw milk, such as tuberculosis, typhoid, and diphtheria. Today pasteurization continues to ensure the safety of milk.
The process is named after the French scientist Louis Pasteur, who in the 1860s showed that heating wine and beer prevented spoilage. In 1886 German chemist Franz von Soxhlet suggested that milk should also be pasteurized to protect consumers. By the 1920s pasteurization had become standard practice in many countries and played a key role in reducing infant deaths and milk-borne epidemics.
Process
Raw milk can contain harmful bacteria, or pathogens, that may cause illness. Pasteurization works by briefly heating milk to a controlled temperature and then cooling it again, which destroys these microbes without sterilizing the milk or altering its basic qualities. The most common method, called high-temperature–short-time (HTST) pasteurization, heats milk to about 72 °C (162 °F) for 15 seconds. Another method, ultra-high-temperature (UHT) pasteurization, heats milk above 138–150 °C (280–302 °F) for a few seconds.
Safety and shelf life
Pathogens such as E. coli, Salmonella, Listeria, and Campylobacter can be present in raw milk and may cause foodborne illnesses. Between 1998 and 2018, the U.S. Centers for Disease Control and Prevention (CDC) documented more than 200 outbreaks linked to raw milk, resulting in thousands of illnesses and hundreds of hospitalizations. These germs are especially dangerous for children, pregnant women, older adults, and people with weakened immune systems.
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Pasteurization has reduced the risk of illness from milk. A study of American milk consumption between 1999 and 2013 estimated that fewer than one illness occurred for every two billion servings of pasteurized milk or milk products consumed. By lowering the number of microbes present, pasteurization slows spoilage, though it does not eliminate it entirely. Properly refrigerated pasteurized milk usually lasts about two weeks, and UHT milk, when combined with special packaging, can remain shelf-stable for months if unopened.
Nutrition and taste
Scientific studies show that pasteurization does not significantly affect the main nutrients in milk. Proteins, fats, and minerals remain unchanged, and only small losses occur in certain heat-sensitive vitamins, such as vitamin C. Since milk is not a major source of vitamin C, this loss has little nutritional impact. Pasteurized milk continues to provide calcium, protein, and other essential nutrients.