By Joy Gaze - 16 April 2013

The evaluation of the effectiveness of any food preservation process to reduce the target microbiological population is complicated. It is often linked to product safety and consequently is very important to all concerned.

It is fair to say that no two process validations are exactly the same. Mainly because of the diversity of processing equipment and the vast range of food products currently produced world wide. This can be very challenging, and requires expertise and knowledge of the microbiology involved.

The principles of any validation should include the demonstration that the thermal process produces sufficient lethality to achieve an adequate microbiological reduction to ensure food safety and product stability during shelf life.

Typically this is achieved by the use of a harmless surrogate microorganism that mimics the heat resistance characteristics of the harmful microorganisms - the latter usually having the potential to cause food poisoning.

Our research and contract studies in this area are very much industry driven, and have taken us far and wide – to regions such as the USA, South Africa, Australia, New Zealand, Asia, and most of Europe. During that time it has been great to work with many highly respected scientists in all aspects of research, evaluation, calculation and interpretation of data for thermal process validation.

So, what might the reasonable expectations be of a process validation?

• Evaluation of the criteria used for the choice of target microorganism and subsequent surrogate for use in testing
• Confirmation of the suitability of the heat treatment
• Confirmation that the number of log reductions of the surrogate microorganism achieved meet the minimum requirements for the safety and stability of the product

Our approach to industry enquiries would include a preliminary evaluation pre-validation assessment/audit, which could include a site visit, dependent on the format and amount of information and data available for discussion on the process. We can do laboratory based trials if a proof of principle approach is required, and we have substantial pilot processing facilities available and space to house other equipment if larger scale work is preferred. We have innovative techniques to simulate foods and microbiological contamination of them. We are also involved with system development to optimise energy use and lethality achieved.

In my opinion one of the most critical parts of any process validation is the interpretation of the microbiological data produced. There are many clues that can be derived from these data and rarely is this straight forward (I realise that we microbiologists have quite a reputation for saying this, but it is totally true!). It is the data interpretation and context setting that have helped many food companies move on to develop new products, ensure the safety of a vast range of product formulations and indeed solve problems related to unexpected microbiological issues, therefore avoiding the long term costs that such issues can incur.

If you would like to discuss any aspect of microbiological process validation, please get in touch with Rob Limburn.

Find out more about our food and drink processing facilities.