the Uht pasteurisation process
The whole aim of pasteurising milk is to kill any harmful bacteria and disable the deadly enzymes to ensure that it is safe for consumption. There is one basic rule for the overall process of pasteurisation, which is, 'the hotter the temperature and shorter the time, the longer the milk will last'. From this rule, 2 variations of the pasteurisation process have been formed, high-temperature short-time (normal/HTST) pasteurisation and Ultra High Temperature (UHT) pasteurisation.
The process of Ultra High Temperature Pasteurisation is a heat treatment process which is overall quite simple. It requires a special machine called a pasteuriser. A pasteuriser is a piece of machinery that lets you pour milk into one end, where the milk then flows between a set of heating pipes or plates, then between a set of cooling pipes, before emerging from an outlet pipe into the bottles and various sterilised containers.
UHT Pasteurisation is a slightly different process to HTST pasteurisation. Instead of heating the milk to 72 degrees Celsius for 15 seconds, UHT requires heating the milk to 141 degrees Celsius for only 1-2 seconds.
There are two principal methods of the UHT process, direct heating and indirect heating.
No matter which UHT Pasteurisation process is used, the result is of course, the creation of long-life milk which has a shelf life of 6-9 months if stored correctly and left un-open.
- Direct heating: direct heating is when the milk is heated by direct contact with steam. This steam, also known as culinary steam, has been filtered and had all impurities removed. It is injected into the milk, followed by a rapidly quick cooling of air in the chamber where the milk is being kept. The major advantage of direct heating is that the milk is exposed to the high temperature for a short amount of time, meaning less nutrients are lost.
- Indirect heating: is when the milk and heating source do not make any contact, but instead separated by certain types of heating equipment such as heating plates and gaskets. This process is cheaper and more energy efficient.
No matter which UHT Pasteurisation process is used, the result is of course, the creation of long-life milk which has a shelf life of 6-9 months if stored correctly and left un-open.