In Summary
- Testing of processing environments for foods (such as fish products) that support growth of L. monocytogenes is a legal requirement.
- Fish can be a source of L. monocytogenes, especially in the gills, where L. monocytogenes can be concentrated.
- Collection of environmental samples before commencement of processing is considered a good practice. This is because it checks cleaning effectiveness and provides assurance that equipment was in an appropriate condition for processing.
- Sample collection during processing is also a good practice.
- With all isolates of L. monocytogenes that are obtained from a processing environment, identifying the strain (i.e. via typing) is important, to identify possible historical persistence of the same L. monocytogenes strain.
Article five of Regulation EC 2073/2005 makes it a legal requirement that food business operators manufacturing ready-to-eat foods, which may pose a L. monocytogenes risk for public health, must sample their processing areas and equipment according to the ISO 18593 standard. It is important that swabs are soaked in neutraliser before samples are collected so that chemical residues on sampled surfaces do not kill bacteria during transit to the testing laboratory. Guidelines have been produced to aid sampling food processing areas and equipment for the detection of L. monocytogenes.
Swabs taken from production areas and equipment will show whether cleaning and disinfection is being carried out effectively.
Where results for swabs are not satisfactory (i. e. L. monocytogenes is detected), FBOs must investigate the cause of the problem and take action to prevent a recurrence. Consideration should be made for:
- A review of production records for the whole process to check whether food safety procedures have been followed. The review should include checks on raw materials, processing temperatures, cleaning records etc.
- A check of cleaning procedures for the process and production areas. Where necessary, processing areas or equipment should be deep cleaned and disinfected before being used again.
- Staff hygiene and assessment of the current training programme to ensure it is adequate and if staff need updated training.
- Checking previous microbiological sampling and environmental swabbing results. You should also look at results for similar products to see if there are problems related to particular equipment or production areas.
- You should also review your food safety management procedures to see if they need to be updated.
The results of your investigation and details of the action you take should be written down.
Following the investigation, you will need to decide if there is a need to increase the frequency of sampling or swabbing, to confirm that the action you have taken has been successful.
Analysis of sample reports should not be limited to dealing with unsatisfactory results but should include the investigation of “trends”; for example, where results deteriorate over a period of time. As part of this process, sample results for Listeria species will provide you with useful indication of overall hygiene standards.
For more guidance see: Shelf life of ready to eat food in relation to L. monocytogenes - Guidance for food business operators, 2010, ISBN-13 978-1-901798-17-3
If you do not have the relevant technical expertise to make ready-to-eat foods safely then you are strongly recommended to seek relevant expert advice.
