- Low temperature pasteurization
- High temperature pasteurization
- Extended shelf life
- Ultra-high temperature
Thermisation is done in large dairy facilities through Heat treating equipment to increase the keeping qualities of milk before subjecting it to further processing. Large dairy farms find it difficult to use all the incoming milk immediately after reception so that the milk undergoes the thermisation process to prevent the growth of bacteria. In thermisation, the product is heated to a temperature that is below pasteurization temperature for about 15 seconds. After heating, the product is cooled to a temperature of 4oF or below to prevent aerobic spore-forming bacteria from multiplying.
Low temperature pasteurization
In the process of low temperature pasteurization, milk is pumped from a balance tank into Heat treating equipment like a plate heat exchanger where it is heated to 72oC for 15 seconds to kill bacteria and to achieve a product that is very similar in terms of nutritional value and taste. Cooling is achieved through ice water or glycol.
High temperature pasteurization
This process requires milk to be pumped from a tank to Heat treating equipment where it is heated at a temperature of 87oC for 15 seconds after which it is cooled down to 5oC with cold water or glycol. Heating is achieved through a plate heat exchanger with hot water.
Extended shelf life (ESL)
This process is applied only to the dairy industry for the extended shelf life of milk which is more than that of a regular product. During the heat treatment process, milk retains its taste as fresh milk but its life has been extended. Generally, the extension can achieved for 7 to 30 days according to the sterility of the production environment downstream of the chosen technology.
Ultra-high temperature (UHT)
In this heat treatment process, liquid products achieve a continuously produced aseptic product with a very long shelf life. The advantage of UHT can be found on chocolate milk and lactose-free milk that can be transported and stored without the need for cooling. The product is heated on the Heat treating equipment at a temperature of 135oC to 145oC from 0.5 to 4 seconds.
This process is the ultimate form of heat treatment where all living cells and microorganisms are destroyed so that the product will have an extended shelf life of 6 to 36 months. Sterilization takes place after the packaging phase wherein both the product and the container that is used for packaging are transferred to Heat treating equipment (retort system or autoclave) with a temperature of 110oC to 125oC for 10 to 30 minutes. As long as the seal has not been broken, the product will be safe during the whole length of its extended shelf life.