Milk is often pasteurized to help it stay fresh for longer. Describe the process of pasteurization and explain how it helps to preserve milk?

Answer 1

The process that gives the milk a longer shelf life is called ultrahigh temperature (UHT) processing or treatment, in which milk is heated to 280 degrees Fahrenheit (138 degrees Celsius) for two to four seconds, killing any bacteria in it.

Compare that to pasteurization, the standard preservation process. There are two types of pasteurization: "low temperature, long time," in which milk is heated to 145 degrees F (63 degrees C) for at least 30 minutes*, or the more common "high temperature, short time," in which milk is heated to roughly 71C and then drastically cooled for at least 15 seconds.

The different temperatures hint at why UHT-treated milk lasts longer: Pasteurization doesn't kill all bacteria in the milk, just enough so that you don't get a disease with your milk mustache. UHT, on the other hand, kills everything.

Retailers typically give pasteurized milk an expiration date of four to six days. Ahead of that, however, was up to six days of processing and shipping, so total shelf life after pasteurization is probably up to two weeks. Milk that undergoes UHT doesn't need to be refrigerated and can sit on the shelf for up to six months.

Regular milk can undergo UHT, too. The process is used for the room-temperature Parmalat milk found outside the refrigerator case and for most milk sold in Europe.

Additional InformationIn the U.S., retailers are not packaging the milk and dating it - the dairy/processor dates the milk. I have seen HTST fluid milk coded with sell-by dates anywhere from 10 days to 2 weeks.

Answer 2

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