Text B. PASTEURIZATION

The value of heat for the preservation of foods has been known for thousands of years, but it was not realized until the 19th century that a very mild heat treatment, far below the boiling-point, made liquid foods such as milk keep much longer. The discovery followed the work of the French scientist Pasteur on wine and beer. The process, called after him "pasteurization", is a carefully controlled mild-heat treatment. It was found that the process served two purposes: it prevented the souring of milk, and it destroyed the dangerous disease germs which occur in some samples of milk.

Milk is rendered free of pathogenic bacteria by pasteurization. Milk is heated to a specified temperature and held at that temperature for a specified time. (145°F for 30 min when milk is pasteurized in a vat or at least 161°F for 15 sec when milk is pasteurized continuously).

Pasteurization on a batch operation requires a jacketed vat where steam or hot water can circulate and heat the milk. This treatment requires the longer times at lower temperatures to accomplish pasteurization (LTLT pasteurizer). Modern methods of processing milk and milk products utilize the high-temperature short-time (HTST) pasteurizer.

In Europe and to a limited amount in the United States, milk and milk products may be ultra-heat-treated (UHT). This process may use equipment similar to that used for HTST. The UHT processing requires a minimum heat treatment of 280°F for 2 sec. UHT dairy foods have extended shelf-life because all of the bacteria that would survive even HTST pasteurization have been destroyed.

VII. Find the English equivalents to the following Russian words:

1. Кратковременный метод при высокой температуре. 2. Тепловая обработка молока при сверхвысокой температуре. 3. Метод длительной тепловой обработки молока при температуре.

1. LTLT; 2. HTST; 3. UHT

VIII. Read the texts and speak on the problems given below: