Pasteurization
Pasteurization is a process that uses heat to kill microorganisms. While the French chemist Louis Pasteur (1822-1895) first applied this process to wine, pasteurization is more usually recognized as being a treatment for milk.
Pasteur was called upon to tackle some of the problems plaguing the French wine industry. Of special concern was the spoiling of wine. This caused great economic loss and tarnished France's reputation for fine vintage wines. Vintners wanted to know the cause of l'amer, a condition that was destroying the best burgundy wines. Pasteur looked at wine under the microscope and noticed that when aged properly, the liquid contained little spherical yeast cells. When the wine turned sour, however, there were numbers of bacterial cells producing lactic acid. Pasteur suggested heating the wine gently at about 120 degrees. This killed the bacteria that produced lactic acid and let the wine age properly.
A Second Revolution
Pasteur's book Etudes sur le Vin ("Studies Regarding Wine") was published in 1866. It was a testament to two of the researcher's great passions—the scientific method and wine. Pasteur suggested that greater cleanliness was needed to eliminate bacteria; this could be done with heat. Some wine-makers were aghast at the thought, but doing so solved the industry's problem.
Milk Joins the Revolution
With the practice of heating wine to kill bacteria firmly established, researchers turned to other liquids like milk. The idea of pasteurization was born. Several decades later in the United States, the pasteurization of milk was championed by American bacteriologist Alice Catherine Evans (1881-1975), who linked bacteria in milk with the disease brucellosis (a type of fever found in different variations in many countries). Pasteurization is now applied to most liquid food products produced commercially.