How it began
The process is named for the French scientist Louis Pasteur. In the 1860s he demonstrated that abnormal fermentation of wine and beer could be prevented by heating the beverages to about 57 °C (135 °F) for a few minutes. The finding came out of his studies of fermentation, in which he helped brewers and winemakers improve their beverages and found that microorganisms were responsible for wine turning sour.
Before it existed
Before Pasteur's research, the scientific community widely accepted spontaneous generation, the idea that microorganisms could arise on their own from nonliving matter. Using sterilized, sealed flasks, Pasteur showed that microorganisms developed only when contamination was introduced from outside. Nicolas Appert had already preserved food by heating it in sealed containers, but without an explanation of why it worked.
How it works
Pasteurization heats a food or drink to a set temperature for a set time. It uses temperatures usually below 100 °C and does not destroy all microorganisms or spores, unlike sterilization. Milk is typically held at 63 °C for 30 minutes, or at 72 °C for 15 seconds, times and temperatures chosen to destroy Mycobacterium tuberculosis and other heat-resistant, disease-causing organisms. The treatment also destroys most spoilage organisms and so extends storage time.
How it spread
Pasteurization of milk became widely practiced in several countries, notably the United States. The first commercial milk pasteurization plant in the United States was established in the early 20th century by the physician and public health activist Charles North, using the batch process. Later, continuous flow methods passed milk through heat exchangers and then cooled it rapidly.
What lasted
People who consume unpasteurized milk products face a significantly higher risk of brucellosis, salmonellosis, tuberculosis, streptococcal infections, and diphtheria than those who consume pasteurized products, according to Britannica. Pasteur's work on germs also allowed Joseph Lister to develop antiseptic practice in surgery.
Where it stands today
The process is applied to milk and to many solid and viscous foods and drinks. Ultrahigh-temperature treatment heats milk or cream to 138 to 150 °C for one or two seconds, allowing storage without refrigeration for six to nine months. The shelf life of a pasteurized product is usually shorter than that of a sterilized one.
