pasteurization(redirected from unpasteurized)
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pasteurization(păs'cho͝orĭzā`shən, –rīzā`shən), partial sterilization of liquids such as milk, orange juice, wine, and beer, as well as cheese, to destroy disease-causing and other undesirable organisms. The process is named for the French scientist Louis PasteurPasteur, Louis
, 1822–95, French chemist. He taught at Dijon, Strasbourg, and Lille, and in Paris at the École normale supérieure and the Sorbonne (1867–89).
..... Click the link for more information. , who discovered in the 1860s that undesired fermentation could be prevented in wine and beer by heating it to 135°F; (57°C;) for a few minutes. Milk is pasteurized by heating it to about 145°F; (63°C;) for 30 min or by the "flash" method of heating to 160°F; (71°C;) for 15 sec, followed by rapid cooling to below 50°F; (10°C;), at which temperature it is stored. The harmless lactic acid bacteria survive the process, but if the milk is not kept cold, they multiply rapidly and cause it to turn sour.
the heating of liquids or foods generally to a temperature of 60°-70°C for 15–30 min. In the process, nonspore-forming bacteria are destroyed, but complete sterilization does not result since bacterial spores can withstand such heating. Proposed by L. Pasteur, the method is mainly used to preserve food products that cannot tolerate heating to higher temperatures.
Milk, wine, beer, and other beverages and various foods are pasteurized on an industrial scale. It is recommended that once they are pasteurized, they be kept at a low temperature in order to prevent the germination of bacterial spores.
A related process is fractional sterilization, or tyndallization. After routine pasteurization, the product is cooled and kept for some time at room temperature. When the surviving spores begin to germinate, the product is pasteurized again. Pasteurization is sometimes repeated three or four times.
Milk, cream, juices, and other beverages are pasteurized in centrifugal, tubular, or lamellar pasteurizers. The product is quickly and briefly heated to comparatively high temperatures (up to 100°C) as it continuously flows in a thin layer between the heating surfaces. It is then poured into hermetically sealed containers. Foods that are already bottled or canned are pasteurized by heating with steam while the containers are constantly rotated. Pasteurization of already packaged products using high-frequency sources of heat is a promising development.