Pasteurization
3 Minutes
Learn about milk pasteurization for kids, exploring how milk is collected, tested, heated, and cooled to last longer. A science lesson in English.
- How milk is collected, transported, and tested for quality
- How heating and quick cooling destroy harmful bacteria
- HTST and UHT pasteurization methods and packaging
What this lesson teaches
Pasteurization is a process where milk is heated to a specific temperature for a set time and then quickly cooled to destroy harmful bacteria. While raw cow milk spoils in just one day, pasteurization prevents microbes from multiplying and allows milk to stay fresh for weeks or even months.
From farm to factory
- Dairy farms collect milk either by hand or by using machines that can milk many cows at the same time.
- The collected milk is poured into large stainless steel containers and transported to the milk processing factory.
- Factory workers take test samples of the raw milk to perform a strict quality test.
- If the milk fails the quality test, it is rejected right away, but approved batches move forward for pasteurization.
How heating and cooling work
Heating milk targets every particle to destroy dangerous microorganisms. For example, if a cup of milk contains one hundred bacteria, heating destroys ninety-eight of them, but the remaining two would quickly multiply if left alone. Rapidly cooling the milk down immediately stops those surviving bacteria from reproducing. This destroys harmful bacteria such as Salmonella, Listeria, Campylobacter, and Staphylococcus aureus, which cause illnesses like tuberculosis, diphtheria, and Q fever.
Two methods of pasteurization
- High Temperature Short Time, or HTST, heats milk to 72 degrees Celsius for 15 seconds and then cools it down to 4 degrees Celsius.
- Milk treated with the HTST method stays fresh without spoiling for two to three weeks.
- Ultra Heat Treatment, or UHT, heats milk to 125 degrees Celsius for just two seconds before cooling it to 4 degrees Celsius.
- The UHT process extends the shelf life of milk so that it lasts up to nine months without spoiling.
Packaging and milk consumption
After pasteurization is complete, automated packaging machines fill the milk into packets or plastic jugs and seal them tightly. These sealed containers are delivered to local stores, where they are kept in refrigerators until people buy them. This pasteurized milk is consumed directly or used to make everyday foods like tea, coffee, curd, cheese, milk cream, milkshakes, and chocolates.