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The application of validation principles to continuous thermal and non-thermal processing

The beauty of continuous thermal processing is that it allows a large quantity of product to be processed in a short time. It is also possible to minimise unwanted chemical changes if the product is processed at the highest possible temperature for the shortest time needed to achieve the required lethality. As a result, a profitable, high quality product can be produced from continuous thermal processing. Continuous non-thermal processing offers alternative mechanisms to inactivate the microorganisms. This can potentially reduce/avoid any adverse effects resulting from high temperature exposure, thus enabling high quality product to be produced.


In an attempt to drive quicker and larger production throughput, the risk of producing undercooked products can arise. Therefore, it is of paramount importance for food manufacturers to be able to confidently prove that their large and rapid food production is safe. A validation study helps to provide scientifically robust evidence to support such claims. The validation study should be considered as an intrinsic part of a HACCP system covering the safe production of food products.


This white paper describes how validation principles are applied in continuous thermal processing (such as heat exchangers, hot filling and pasteurisation tunnels) and in continuous non-thermal processing (such as high pressure processing, pulsed electric fields and ultraviolet light). For a more indepth analysis on any specific process please contact us. We can provide technical support, advice and training.


The principle of thermal process validation


From a product safety point of view, the thermal validation principle ensures that, in the worst case scenario, the slowest heating point in the food attains a specified thermal process (time and temperature) that has proven to be sufficient to reduce a given target microorganism to an acceptable level, should it be present.


Continuous flow heat exchangers


In a continuous heat exchanger system, the slowest heating point in the food is often difficult to identify and measure. This is one of the reasons that lethality contribution in the come-up and cooling phases are not considered in the overall declaration of lethality. The delivered lethality is only considered in the holding (tube) section of the heat exchanger.