Pasteurization is a process of treating foods to kill microorganisms that cause food to spoil. Pasteurization is named after Louis Pasteur, and is most commonly associated with processing milk and other dairy products. Traditional pasteurization is performed by heating a product just enough to kill microorgnisms, but not enough to destroy the taste. Sometimes the term cold pasteurization is used to refer to irradiation (as described above). Ultraviolet (UV) pasteurization uses ultraviolet light.
Pasteurization has two benefits; one is making products safer by killing dangerous organisms and the other is increasing the keeping quality, or shelf life of products. Pasteurization is also the process that allows some, usually dairy, products to be stored without refrigeration until opened.
Pasteurization is more controversial for foods other than dairy, such as beer or fruit juice, because it has potential to effect taste and nutrition. For example all beer sold in the US is pasteurized, while beer sold in much of Europe is not and has a distinctly different flavor.