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Microbiological aspects and considerations of a range of process technologies

The development, evaluation, commissioning and validation of new process technologies has one common goal, which is to ensure that the technology is capable of adequately reducing the number of microorganisms associated with the products.

This white paper looks in general at a very complex area – the interaction of product, packaging and process type and how they combine to enable microbial numbers to be adequately controlled.


The type of processing technology will dictate the range of products likely to be preserved using this equipment. For example, drinks, ready meals, nuts and seeds or jams would all require processing using different technologies. Similarly the microbial loading of these different raw materials will vary considerably in terms of the range of microorganisms potentially present and the concentrations of each. These would in turn change considerably according to whether the raw materials were chilled and held individually or had a mix and hold stage.

The source of these raw materials will also have a potentially major impact on the level of microorganisms present and consequently on the level of the challenge to the processing technology. The lethal effect from the process could be from a combination of parameters, i.e. heat, pressure differentials, shear forces, moisture variation, oxygen availability. Some processes will achieve considerable lethality by one single treatment, whereas other will require the combined cumulative lethality of several during manufacture.

If the raw materials are handled or stored differently to the standard conditions this has the potential to more severely challenge the manufacturing system.

Food product formulation

This stage of all food manufacture is critically important from the microbiological perspective. Historical food poisoning issues have shown that even the most minor formulation changes have the potential to allow microorganisms to survive or grow when they would otherwise have been reduced or inhibited, e.g. changes to the types of sweeteners used.

This particular aspect has to be considered very carefully when developing new technologies because often the traditional preservation pathway is modified to incorporate the new concept. Indeed on occasions the new technology has been developed to specifically change the eating qualities of the food, for example giving a milder treatment but incorporating more hurdles. In this example a clear knowledge of the combined effects would be essential to prevent survival and growth. The nature of how the treatment effectively destroys/reduces/inhibits the microorganism will be affected by cross contamination by materials affecting the product, such as the addition of extra water perhaps from condensation, or leakage into containers from untreated ingredients.