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Validation of GMP Programs 

Good Manufacturing Practices (GMPs) or prerequisite programs are the foundation of an effective food safety program such as Hazard Analysis Critical Control Point (HACCP). HACCP requires scientific evidence that hazards associated with ingredients, products, or processing steps are controlled. To ensure that your GMPs are controlling hazards related to the personnel and environment, use an environmental monitoring program to provide scientific evidence. 

Environmental monitoring program

An environmental monitoring program provides scientific evidence to managers, auditors, employees and clients that the resources and effort put into providing clean uniforms, following traffic patterns, effective hand washing , cleaning and sanitation procedures, sanitary equipment design, etc  are effective in providing an environment for the manufacture of safe food.

The environment in a food processing plant can provide sufficient time, moisture, nutrients and other essential conditions that allow pathogenic and spoilage microorganisms to grow and contaminate food products. It is not good enough that facility floors, walls and equipment simply look clean; they must also be microbiologically clean.   

Where to start?

For an effective environmental monitoring program, you need to define the following elements:

  • Sampling method: Use the correct environmental hygiene monitoring screen or test method for your type of process.  This could include the use of swabs, sponges, slides, strips or other diagnostic test kit tools. Sampling needs to be performed by trained personnel. You can use the services of external laboratories. They will be able to recommend the method of analysis best suited to your operation. If you need technical help, contact foodsafety@gov.mb.ca; or 204-795-7968 in Winnipeg.
  • Location of sampling: For routine sampling, find environments where microorganisms tend to flourish, including:
    • food contact surfaces (ex: conveyors, tables, knives, packaging)
    • processing equipment (ex: slicers, mixers)
    • non-food contact areas (ex: drains, floors, equipment support framework)
    • air in the production area

In addition, hard-to-reach places, such as the inside of equipment, gaskets, hinges, etc., should be sampled periodically to prevent undetected contamination. Consider taking samples of employees hands when frequent hand contact with food is required (ex: in packaging areas), as well as sampling aprons or uniforms.  

  • Frequency: This will depend on the type of food processed.  Initially, samples may be taken once a week for at least one month after cleaning, to assess baseline microbial load. Then, you can change the sampling frequency, depending on the initial results. An environmental monitoring program is a long term commitment.
  • Number of samples: It is important to take an adequate number of samples.  If the sample size is too small, the chance of detecting a problem is reduced. To help you reduce the cost of analysis, you can collect samples from different locations and combine them for analysis. This is called a composite sampling. If problems are found, you can analyze individual samples to identify the source of microbial contamination. 
  • Test method selection:
    • Coliform and Aerobic Plate Count (APC) are recommended methods because they are non-selective, and can enumerate large numbers of bacteria.
    • Yeast and mould plates (potato dextrose agar with chloramphenicol or dichloran rose bengal chloramphenicol) are recommended for air sampling in surrounding processing areas. Generally, plates are exposed to the air for 15 to 45 minutes.
    • You may consider testing for pathogens such as Listeria monocytogenes, Salmonella, Escherichia coli O157:H7 or coagulase positive Staphylococcus. To prevent a food recall, you may hold food products until you have the test results.
  • Sampling time: Normally, samples are taken after the cleaning process, which likely occurs after production is finished. It is recommended that sampling be done when equipment is completely disassembled. Sampling hidden sites can reveal places where improper cleaning occurs.
  • Sample analysis: The samples collected can be analyzed by an external laboratory or in your facility. You can buy a variety of tests that are already prepared with culture media. They require incubation, using the manufacturer's instructions, and will provide results of microbial counts. For statistical relevance in your analysis, replication of the testing (between five and 25 samples) is suggested.

Interpreting microbial results  

There are different ways to present microbial results. Examples of different formats include:

  • absolute number (ex: 250 organisms)
  • CFU/gram (colony-forming units per gram)
  • Scientific notation (ex: 2.5 X 102  (the base is 10 and the exponent is 2 — it is 10 to the power of 2), which converts to 2.5 X 10 X 10 equals 250 organisms)  

Baseline specifications

Collecting data for one to three months, depending on sampling frequency is usually enough to determine a baseline for most microorganisms. Your baseline may be set at a specific number or, if testing for pathogens, can simply be the presence or absence of them. 

Cleaning and sanitizing should reduce microbial loads to levels of less than 10 CFU per sponge for coliforms, aerobic plate count, yeast and mould, and coagulase positive Staphylococcus on product contact surface before packaging.

CFU per sponge values for other areas, including non-product contact areas (ex: walls, ceilings, pallets, drains, floors, etc.), will vary, depending on the plant and type of product manufactured. Aerobic plate counts of above 10,000 organisms should cause concern and an area with 100,000 organisms should be considered a microbial contaminated site.

Data analysis and validation

It is important that the results are analyzed to ensure proper corrective actions can be taken. Once the samples are analyzed, the baseline data can be displayed on a spreadsheet or graph to demonstrate plant performance. A graph will provide easy visualization of the data.  

When you understand baseline values for your facility, deviations above the baseline may indicate a failure in your plant's system. This could include changes in traffic patterns, personnel practices and inadequate use of sanitizers. You need to establish corrective actions that include: investigating the cause of the failure as well as retesting positive test areas.  Finding the root cause of the problem may lead to a variety of solutions, including repairing the equipment and facility, examining current plant practices and retraining staff. The goal is to prevent reoccurrence.  Once action has been taken, it is important to resample the areas, to ensure the solutions were effective. Documentation must show how the problem was addressed and that the corrective actions were effective.  

It is important to continue to validate GMPs to ensure they are effectively controlling potential food safety hazards.

Related links


For more information, email the CVO/Food Safety Knowledge Centre or call 204-795-8418 in Winnipeg.  


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