pasteurization, process of heating foods, including wines, to a temperature high enough to kill all micro-organisms such as yeast and bacteria. It is named after Louis pasteur, the French scientist who discovered that micro-organisms were alive and the cause of much wine spoilage.
Heat sterilization techniques have improved greatly since the early versions of pasteurization, which often resulted in burnt or cooked flavours in wines treated, particularly those that had not been subjected to complete clarification. Wines are pasteurized by rapid heating to about 85 °C/185 °F for one minute, quick cooling, and return to storage tank or bottling line. Keeping the wine longer, for up to three days, at about 50 °C/122 °F is used to coagulate heat-unstable proteins and to speed ageing in low-quality red dessert wines. Flash pasteurization may also be effected by heating to temperatures as high as 95 °C for a few seconds, followed by rapid cooling. Some wine is hot bottled (at about 55 °C) and allowed to cool slowly or, for utmost effectiveness, closed bottles of wine are occasionally heated to about 55 °C and cooled to room temperature under a water spray. These techniques are relatively brutal, however, and are used only on ordinary wines which have no potential for improvement after bottle ageing. See also kosher wine.