What type of heat treatments can milk undergo?
Four different methods are used to heat treat milk to make it safe and extending the shelf life: pasteurisation; ultra-pasteurisation; ultra-high temperature treatment; sterilisation.
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Appropriate heat treatment limits harmful bacteria that may be present in food and ensures that the food is safe for consumption. Milk can be heat treated through four different methods:
- Pasteurisation involves heating milk to a high temperature (72 °C), followed by rapid cooling to 4 °C.
- Ultra-pasteurisation involves treatment at a higher temperature and products treated in this way may stay fresh for more than 14 days if kept at 4 °C or lower.
- Ultra-high temperature treatment involves heating milk to between 135 °C and 150 °C for two to four seconds and then cooling it to 4 °C or lower. This treatment is used to produce long-life milk.
Sterilisation involves heating filled bottles of milk to between 110 °C and 130 °C for approximately 10–30 minutes, after which the bottles are cooled with cold water. Unopened bottles of sterilised milk keep for a long time without having to be refrigerated. Once opened, it must be treated as fresh milk.