The Armfield Ltd HTST pasteuriser is an accurate miniature version of the industrial unit and has been designed primarily for use with milk although other food liquids can be pasteurised providing their solids content is not too high

Basically, the High Temperature , Short Time process involves heating the process fluid up to a certain minimum temperature (71.7ºC for milk), holding at this temperature for a certain period of time (15 seconds for milk) and cooling down to a suitable storage temperature (less than 10ºC for milk) as quickly as possible

In industry, the outgoing hot pasteurised milk is used to transfer heat to the ingoing cold raw milk as and economy measure. This is done in a heat exchanger known as an interchanger or regenerator

The heater, cooler and regenerator appear in the form of plate heat exchangers and are incorporated on a single framework

After the initial disinfecting process to ensure the system is clean, the liquid to be pasteurised is placed into the feed tank. The feed pump, pumps the liquid to the regenerative section of the heat exchanger. After regeneration it passes to the heating section where it is brought up to pasteurising temperature

Any product not at the required temperature after passing through the hold tube is diverted back to the feed tank by a diverting valve through the action of the temperature controller on the control console

Heating is accomplished using water at a high flow rate only 6 to 8ºC hotter than the pasteurising temperature. The water is heated by an immersion heater in a closed circuit circulation system, also controlled by the temperature controller

The product then passes back through the regenerator and the cooler to storage. The final cooler has been designed to achieve product temperatures below 10ºC provided a chilled water unit is available in the laboratory

The regenerator is capable of producing a high degree of heat recovery by contacting the cold, feed liquid with the outgoing hot pasteurised liquid