Milk Pasteurisation
Short time standard pasteurisation is a process of heating and cooling milk destroying pathogenic material that may be present (Organic Valley, 2014). Milk is pasteurised in a plate heat exchanger consisting of three sections: heating, regenerative heat and cooling as illustrated in figure 1. Furthermore, a set of odd and even chambers are present. The milk entering the even chambers is heated by the milk coming out of the odd chambers which has been heated and pasteurised in the regenerative section of plate heat exchanger (White, 2010). This allows the milk to warm up to temperatures between 57 to 68 degrees Celsius.
In the heating section of the plate heat exchanger the odd chamber passes through hot water that heats the milk to the required pasteurisation temperature of 72 degrees Celsius (White, 2010). The milk then passes through a holding tube at this temperature for 15 seconds (White, 2010). The milk is now pasteurised but requires to be cooled. This is done by going back through the regenerative section cooling down the milk to 32 degrees Celsius. This is as a result of the incoming cold milk going through the even chambers (White, 2010). Lastly, the milk passes through the cooling section by either a coolant or cold water in order for the milk to reach 4 degrees Celsius (White, 2010).
By Arwa Al-Bahadly
Figure 1: Process of Pasteurisation in a plate heat exchanger