Pasteurization

Louis Pasteur invented the food preparation technique named after him, pasteurization, which kills microorganisms, to extend its shelf life.

In pasteurization food is briefly raised to relatively high temperatures, and then rapidly cooled. If the heating and cooling is swift enough the food's taste remains largely the same.

Milk, for human consumption, is almost always pasteurized, in modern times; Microorganisms naturally found in milk will spoil milk -- sour it -- in about a day, if it is not pasteurized.