Autoclave calibration and validation are both vital to food safety. We explain the differences between them.
This article was first published by Food Processing and is reproduced here with their permission.
With the public increasingly concerned about instances of contaminated food reaching retail shelves, it is more important than ever that the food and beverage industry ensures that its products meet the highest standards of microbiological quality. A hazard analysis and critical control points (HACCP) study will invariably identify the autoclave – be it for product sterilisation or quality control laboratory testing – as a potential risk. A failure of product sterilisation clearly has far reaching consequences but a failure of the laboratory steriliser can produce spurious results causing unnecessary product wastage. So how can you be certain that your autoclave is working properly?
When it comes to using steam for sterilisation, it is critical to know that the correct pressures and temperatures have been reached, and that they have been held for long enough to ensure the total destruction of any and all microorganisms, bacteria and spores. This means that the autoclave instruments – temperature and pressure sensors and timers – that control your autoclave must be functioning correctly and producing accurate readings. In other words, are they properly calibrated?
Calibration is about checking that the autoclave instruments read accurately by comparison against a known standard and that the chamber reaches the required temperature for the required time. This testing methodology should be carried out using the protocols which are set out in the international standard, ISO/IEC 17025:2017. The test can be carried out at a number of different sterilisation temperatures and times depending on the customer’s requirements, and confirms that the machine has been calibrated in accordance with UKAS standards by an accredited calibration laboratory such as Astell Scientific. Upon successful completion, you will receive from Astell a certificate of calibration. However, a successful calibration only confirms that the instruments and controls are operating correctly: it does not ensure that the loads placed in the autoclave are actually achieving the specified temperature and time. This requires validation.
Multipoint Validation is a more detailed procedure which records temperature readings at 12 or more points within a specific customer load over a specified time. It may be repeated with different loads. Steam penetration and air removal is of key importance with these tests and so tests are, as far as possible, carried out under worst-case conditions which typically would be an example of the largest load the customer is likely to run.
Analysing the results from multipoint testing enables the validation engineer to set up dedicated sterilisation programmes for the loads, this is particularly advantageous when 'difficult' items are to be sterilised. Once testing is complete and the cycles have been set up, the validation engineer will issue a certified test report detailing all the results from testing. These will include details of cycle times and temperatures, along with photographs of the way in which the contents have been loaded into the chamber to ensure that the operators load in the same way each time. Such validation reports are valuable in providing continuity, particularly when an autoclave has a number of different users, and assist in ensuring reliability and correct use of a steriliser.
Multipoint validation tests should be completed at regular intervals using a UKAS accredited testing laboratory. This is particularly important for ageing autoclaves and will identify when the machine is reaching the end of its life. Once again, the protocols set out in ISO/IEC 17025:2017 should be adhered to.
The food and drink industry around the world is heavily regulated, and failure to meet sterility requirements can have serious repercussions. Regular calibration is a clear routine necessity, but validation ensures compliance. The validation process may sound complicated, but it pays dividends. It establishes documented evidence that shows a high degree of confidence that the sterilisation process will be performed consistently. Astell Scientific has the experience and knowledge to assist customers in specifying the equipment you need. Even if your autoclave is brand new and has been functionally tested and calibrated at the manufacturer’s works prior to dispatch, it is your responsibility to ensure that it operates as intended. Validation is the key to meeting this responsibility and, to this end, regular testing of an autoclave’s performance by an accredited company is recommended as good practice in critical industries such as food and beverage.
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