Top Tips for Developing an Environmental Sampling Plan for Microbiology
1. What’s your objective?
In order to get the best value from the resources used in any sampling plan, it is important to identify the area/s to be included in the plan and understand the objective. The objective may be to confirm the hygiene of a given area and/or products using microbiological techniques, and there will be others.
2. What resources are available?
It is important that it is recognized that the resources include the time of the person conducting the sampling (and any other team members, like engineers) and the cost of any disposables, as well as the laboratory costs and management of the results.
3. Have you got the right people in the team?
At the beginning of the development of the environmental sampling plan, the sites and timings must be established. The best way to determine these are to use a “fresh eyes” approach if there is already a microbiological sampling plan in place, and to use the knowledge of the operation & hygiene team as well as technical/ quality team members.
4. Where are you sampling?
Look at the production of food in its entirety, and identify those areas of interest. The original objective for the sampling plan and the investment made should also be considered when selecting the sampling sites. It may be necessary to dismantle and re assemble equipment, so having the right people on hand will also be an important consideration.
The environmental sampling plan development should consider the following areas to be of interest:
Hand contact surfaces
Product contact surfaces
Services – air & water
Structural sites of interest – where product/water accumulate which could lead to cross contamination, or accumulation of pathogens or spoilage micro-organisms, such as Listeria spp or Salmonella spp.
5. Have you done a risk assessment?
Once all the potential sampling sites have been identified, a risk assessment exercise to determine the frequency of sampling will inform the final sampling schedule.
Higher frequency/risk sites include product contact surfaces and machinery controls, which are in constant use by the operators. The wear and tear on an article such as a chopping board, may increase the risk.
Other sites of interest include indirect contact sites, such as trolleys used to move items of equipment around the production areas, floors, and drains, as well as water outlets and air flow will also need to be considered if these are to be added to the list of types of environmental sampling.
6. When are you going to do it ?
The timing of the sampling will be important, e.g. it may take place before the beginning of the production shift or be an integral part of the production shift, or even at the end of a shift.
7. Have you got a plan?
The frequency of sampling and number of samples will be influenced by the risk assessment, complexity of the site, risk assessment of the product and budget. In addition, any previous microbiological results from environmental or product sources as well as customer expectations or requirements, in the form of specifications, will also influence the frequency and number of samples taken.
With the objective and knowledge of the production site and its processes, list of potential sampling sites and risk assessments, the sampling plans can be created. A typical plan would include machinery buttons, handles and switches, door handles or plates, product contact areas inside machinery, including pipework, and on surfaces, taps and hand washing equipment, trays, and indirect contact areas, as well as floors, trolleys, and drains.
8. How do you know if it’s the right plan?
The plan should have a formal annual review scheduled into the year. The trigger will be in a similar way as a HACCP review i.e. at a predetermined frequency, with trained members of the review team, if any major physical changes, product type changes or additions happen. However, any changes to the environmental plan should be reviewed over a shorter time frame. Naturally, any out of specification results will also trigger a detailed investigation, and these should also inform the review.
Typically, a schedule will run over two or four weeks or three months or even a year. It will include hand and product contact sites on a more frequent basis and indirect and structural sites on a less frequent basis. The plan will be flexible to adapt to trends of poor results and rigorous enough to capture all sites of potential direct and indirect contamination by microorganisms and cross contamination.
Potential sampling sites
Personnel – hand swabs and PPE (personal protective equipment)
Equipment – hand and product contact sites and indirect contact sites, including transitory items such as engineering equipment.
Services – air and water
Environment – structural elements that may create harbourage for pathogens e.g. floors and drains
Product results from finished product, shelf life testing & Intermediate product as well as New product development samples should be considered during reviews and any investigatory work. Raw materials may also be considered as a source of environmental pathogens.