pasteurization

Treatment of food to reduce the number of micro-organisms it contains and so protect consumers from disease. Harmful bacteria are killed and the development of others is delayed. For milk, the method involves heating it to 72°C/161°F for 15 seconds followed by rapid cooling to 10°C/50°F or lower. The process also kills beneficial bacteria and reduces the nutritive property of milk.

The experiments of Louis Pasteur on wine and beer in the 1850s and 1860s showed how heat treatment slowed the multiplication of bacteria and thereby the process of souring. Pasteurization of milk made headway in the dairy industries of Scandinavia and the USA before 1900 because of the realization that it also killed off bacteria associated with the diseases of tuberculosis, typhoid, diphtheria, and dysentery.