By Mark Naylor – 1 December 2016

Process validation is the collection and evaluation of data to establish that a process is capable of consistently delivering safe product. If a product or process is not properly validated, it could lead to unsafe product and potential financial losses.

Although many of the common process validation mistakes in this post are specific to thermal process validations, much of the information is also applicable in other forms of validation work.

• Training: It is important that all individuals responsible for any validation work or report writing are properly trained in both the factory’s operating procedures and applicable industry standards. Non-compliance could mean that the validation results will not be able to provide the necessary evidence when required.


• Starting the validation work too early: We frequently see processes being validated before equipment is fully installed, or before product, packaging and processing specifications have been set. Before commencing any work, it is important that:
  
  a. All equipment and utilities should be fully installed and commissioned, all of the instruments calibrated, and all validation work is performed after any significant maintenance or upgrade work has been undertaken.
  b. Product and packaging specifications have been confirmed (recipe, fill weights, packaging material, loading patterns)
  c. All targets for the validation are pre-defined. These limits should typically be set by an expert who has taken into account various factors such as the type and initial microbial loading present in the raw ingredients. Before commencing any validation work, the targets for the process must be known and measurable.
  d. Unless specifically required (i.e. in some very heat sensitive foods) the process target should always exceed the minimum processing target.
  
  Any changes made to the product (e.g. changes to recipes or fill weights) or process (e.g. installation of wider steam pipe) that may significantly affect the effectiveness of the process will invalidate any previous validation work, and the process should be repeated.


• Failing to set up 'Worst Case' conditions: A common principle of process validation is to challenge a process under its "worst case" conditions - a set of parameters within the upper and lower processing limits chosen to pose the greatest chance of failure. If a process is still able to exceed its processing targets when operating under these less favourable conditions, then all product produced during normal production will probably exceed these limits too. Most mistakes result when the worst case conditions are not adequately identified or when the validation only studies a single condition rather than a combination of many factors. Typical controls used may include reducing the initial product temperature, increasing the product fill weight, using the worst performing loading patterns, and changing the headspace volume.


• Not using enough or unsuitable measurement equipment: In order to understand how a process works, it is important that enough data is collected so that measurements from different locations in the process can be compared simultaneously. The equipment used for the validation must be suitable for the job at hand, so that the readings are meaningful and repeatable. For example, if a short temperature probe is used to measure the temperature of a large meat product, it will not reach the core of the product, so will always overestimate the core product temperature and overestimate the amount of lethality that is achieved. All equipment must have suitable accuracy and be calibrated against a traceable standard, so that readings between instruments can be compared.


• Not enough replication: All trials should have a suitable number of samples, and each set of experiments should be repeated, ideally in triplicate, to ensure that results are reliable and repeatable. It is important that the results from these ‘replicate runs’ are similar to each other, otherwise they do not prove any consistency and more trials should be completed.

Whilst this may not be a comprehensive list, hopefully it will give you some food for thought and help you identify where mistakes in your process validation are being made. Alternatively if you require any help, or would like to discuss any aspects of process validation, please get in touch.