A Guide to Environmental Monitoring

An effective environmental monitoring program (EMP) is a pillar of food safety for validating and verifying the effectiveness of preventive controls within a processing facility. The primary components of an EMP include:  

• Baseline sanitation program to control potential pathogen or allergen harborage sites. 
• Environmental testing program to assess effectiveness of these controls. 
• Evaluation of results and root cause analysis when out-of-specification environmental test results are found. 
• Corrective actions taken based on root cause analysis. 

 

WHY DO ENVIRONMENTAL MONITORING 

In most circumstances, an environmental monitoring program is a requirement established by regulation to ensure manufacturers are controlling environmental pathogens and allergens. Beyond that, customer expectations and food safety auditing schemes generally require environmental monitoring. Environmental monitoring also can be an effective tool to help resolve product spoilage and shelf-life issues. 

Key Considerations for Implementing an Environmental Monitoring Program 

• Raw materials and ingredients can contain pathogens and allergens. 
• Pathogen kill steps in a process should eliminate pathogens but are not effective in eliminating allergens. 
• Materials exiting kill step are subject to recontamination if exposed to the manufacturing environment before final package closure. 
• Processing that does not include a kill step can be at risk for pathogen cross contamination anywhere during the process. 
• Cross contamination may occur between raw and cooked materials. 
• Sanitary condition of the post-kill step environment (product contact and non-contact surfaces, utensils, employees) is a major factor contributing to recontamination. 
• The cleanliness of food contact surfaces is a major factor in the potential for allergen cross contact. 
• Validating the effectiveness of a cleaning and sanitation process is required. 
• Routine verification of cleaning and sanitation effectiveness is required to ensure expected outcomes are achieved when the validated cleaning and sanitation process is used. 
• Both validation and verification activities use environmental monitoring data as evidence of effectiveness. 

When is Environmental Monitoring Required? 

Ready-to-eat (RTE) foods or ingredients exposed to the environment before packaging and that do not receive a control measure to minimize pathogens, will require a sanitation verification activity. All food stock-keeping units (SKUs) that require clean food contact surfaces for allergen removal will require cleaning verification activity. 

 

WHAT ARE THE GOALS OF AN ENVIRONMENTAL MONITORING PROGRAM? 

Primary 

to find pathogens or allergens in the environment before they contaminate product. 

Secondary 

to find spoilage microorganisms in the environment before they affect product. 

Tertiary 

to assess effectiveness of cleaning, sanitation, and employee hygiene practices. 

 

WHAT ARE YOU TRYING TO CONTROL IN AN EMP? 

Salmonella is the target microorganism for environmental monitoring of product-contact and non-product contact surfaces in a low-moisture food manufacturing facility. 

Listeria monocytogenes is the target microorganism for environmental monitoring of product-contact and non-product contact surfaces in a high-moisture food manufacturing facility. 

Allergens that require food contact surface cleaning between SKUs. 

How Do You Achieve Salmonella, L. monocytogenes, and Allergen Control? 

• Thorough cleaning and sanitation. 
• Traffic control of personnel and equipment. 
• Separation of raw and pasteurized product. 
• Separation of allergen containing ingredients/finished products from non-allergen containing products. 
• Air and dust control. 
• Water control. 

  

WHERE TO TEST IN THE ENVIRONMENT? 

A well-designed environmental monitoring program will include samples from various areas throughout your production process. For pathogen control, the focus of an environmental monitoring program should be on the Primary Microbial Control Area. This area is defined as the area subsequent to the lethality step up to the packaging step. For processes that do not have a Salmonella or Listeria lethality step, the entire processing area is considered the Primary Microbial Control Area. For allergen control, the primary focus is to ensure cleanliness of food contact surfaces. 

The Zone Concept 

The simplest way to organize your sampling program is through the use of zones as outlined below. Multiple sampling sites from each zone should be determined (based on your specific facility design and processes) before you begin taking samples. You can rotate sites at each sampling interval to increase coverage in a particular zone. For example, if you have identified 60 potential sampling sites in Zone 2, randomly sample a few of these sites each week, making sure that each site is sampled at least once per month. This system will help you stretch your testing budget while making sure you sample all sites needed to verify program effectiveness. Larger, high-risk facilities will require a greater number of samples and perhaps a greater sampling frequency than smaller, low-risk facilities. 

Identification of Sampling Sites 

Establishment of monitoring locations should be based on previous studies during dynamic conditions. This could include a “gridding” or “mapping” study to determine worst case/most meaningful locations, as well as considerations of all hot spots or high-risk areas. 

Keep a detailed sampling site log and facility map that details locations of sampling sites. The log should contain written detail on how to collect samples from difficult-to-access areas (sites under processing equipment, sites within equipment, overhead fixtures, etc.). Note that the number of sampling sites and number of samples will vary with the type of product, nature of processing scheme, and risk level deemed acceptable. 

Higher-risk products processed in a large complex facility will likely need more samples and a greater sampling frequency than lower-risk products processed in a smaller, more simple processing facility. 

Sampling Frequency 

When first starting, sample numerous sites and use large surface areas to gauge the degree of contamination and identify potential problem areas. 

Increase frequency following adverse events or process changes, such as: 

• Ingredient changes 
• Leaky roof 
• Drain backups 
• Construction events 
• Equipment installation 
• Vermin/pest intrusion events 
• Whenever pathogen or allergen found 

Testing Frequency 

Testing frequency should be based on: 

• History and trends 
• Features of the plant 
• Type of product and volume 
• Plant layout 
• Product flow 

 

ZONE MANAGEMENT 

Zone 1: Direct Product Contact Surfaces 

Surfaces where food product is exposed to the environment before final package closure. 

Locations 

Tables, conveyor belts, buckets, fillers, hoppers, utensils, employee hands and gloves, items and surfaces directly over or in close proximity to direct food contact surfaces such as lights fixtures and piping, compressed air lines, and water filters. 

Tests 

Pathogen testing of Zone 1 surfaces is a controversial subject due to potential for recalls if found (Salmonella and/or L. monocytogenes). As a result, many decide to test for appropriate indicator bacteria (Listeria species, aerobic plate count, coliform count, or total Enterobacteriaceae count). Testing for allergens requiring removal is appropriate. 

Frequency of Testing 

Daily or weekly depending on risk. 

Minimum Number of Samples 

Depends on facility size, process complexity, and level of risk. 

Program Validation 

Necessary if only using indicator (microbial indicators, ATP) testing in the routine program. Validation includes periodic testing for pathogens and allergens of concern and the indicator to develop a correlation between the level of the chosen indicator and the prevalence of the pathogen or allergen. 

Product Disposition 

All product produced on the line tested should be held until final results are received when testing any Zone 1 sites for pathogens or allergens. 

Zone 2: Non-Product Contact Surfaces Close to Zone 1 Surfaces 

Locations 

Equipment frames, drip shields and pans, control panels and buttons, overhead fixtures and piping not directly over or in close proximity to food contact surfaces, computer screens, maintenance tools. 

Tests 

Salmonella and/or L. monocytogenes, indicator bacteria (Listeria species, aerobic plate count, coliform count, total Enterobacteriaceae count). Allergen testing is typically not done on Zone 2, 3, or 4 surfaces unless risk assessment justifies. 

Frequency of Testing 

Weekly. 

Minimum Number of Samples 

Depends on facility size, process complexity, and level of risk. 

Zone 3: Non-Product Contact Surfaces in Open Processing Area 

Locations 

Floors, walls, ceilings, drains, hoses, cleaning equipment including brooms and brushes, air handling units, condensate drip pans, carts, pallets, forklifts, trash cans, foot baths, sink area including soap and towel dispensers. 

Tests 

Salmonella and/or L. monocytogenes, indicator bacteria (Listeria species, aerobic plate count, coliform count, total Enterobacteriaceae count, lactic acid bacteria count). Allergen testing is typically not done on Zone 2, 3, or 4 surfaces unless risk assessment justifies. 

Frequency of Testing 

Weekly. 

Minimum Number of Samples 

Depends on facility size, process complexity, and level of risk. 

Zone 4: Support Facilities Not in Open Processing Area 

Locations 

Bathrooms, locker rooms, cafeteria and break rooms, office rooms, hallways, warehouse, loading docks, maintenance shop, storage areas. 

Tests 

Salmonella and/or L. monocytogenes, indicator bacteria (Listeria species, aerobic plate count, coliform count, total Enterobacteriaceae count, lactic acid bacteria count). Allergen testing is typically not done on Zone 2, 3, or 4 surfaces unless risk assessment justifies. 

Frequency of Testing 

Monthly to quarterly. 

Minimum Number of Samples 

Depends on facility size, process complexity, and level of risk.

 

ASEPTIC COLLECTION OF ENVIRONMENT SAMPLES

Collecting environment samples in an aseptic manner is critical to ensuring the quality of the testing results. If the person collecting the samples contaminates the specimen, the laboratory result will not accurately reflect the condition of your manufacturing environment.

Key points for sample collection include: 

• Don’t cross contaminate your sample with dirty hands, dirty attire, or dirty sample collection devices. 
• Send chilled samples to the lab ideally within 24 hours. 
• If unable to deliver within 24 hours consider dry sample collection using dry sponges/swabs. 
• Make an effort to find hard-to-clean areas. 
• Use results to educate employees. 

Sampling Tools 

There are multiple commercial sampling tools available for use. This instruction addresses three of the most common types. Most tools are pre-sterilized with a transport buffer. It is important to match the correct sampling tool for the target analyte – micro tools for collecting microorganisms and allergen tools for collecting allergen residue. 

Sponge in Bag 

A small sterile sponge (about 1” x 2”) is pre-moistened with a transport buffer in a sealed bag. Some vendors attach a pair of sterile gloves to the sponge bag. 

Sponge with Handle (“Spongesickle” or “Stick-Sponge”) 

A small sterile sponge is attached to the end of a long plastic handle; the whole unit is contained in a sealed plastic bag containing a small amount of transport buffer. 

Swab (“Q-tip” style) 

A small sterile pre-moistened swab resembling a Q-Tip is contained in a tube with transport buffer. 

Sponge/Swab Transport Buffers 

The most common transport buffers contain various agents that act to neutralize common sanitizers that might be present in the collected samples. Any residual sanitizer could have bactericidal and/or bacteriostatic activity, which could negatively impact the ability to count or recover the target microorganisms by enrichment and/or by direct impact on downstream detection methods. The three most common neutralizing buffers are Letheen broth, Neutralizing buffer, and D/E broth. Their neutralizing components and sanitizers inactivated are listed below. 

Letheen Broth 

• • Lecithin – quaternary ammonium compounds 
  • Polysorbate 80 – substituted phenolics 
  • Both together – ethanol 

Neutralizing Buffer 

• • Sodium thiosulfate – iodine and chlorine 
  • Aryl sulfonate complex – quaternary ammonium compounds 

D/E Broth 

• • Sodium thioglycolate – mercurials 
  • Sodium thiosulfate – iodine and chlorine 
  • Sodium bisulfite – aldehydes 
  • Polysorbate 80 – substituted phenolics 
  • Lecithin – quaternary ammonium compounds 

Typical Sanitizing Agents	Letheen Broth	Neutralizing Buffer	D/E Broth
Quaternary Ammonium Compounds (Quats)	Yes	Yes	Yes
Iodine Preparations	Somewhat	Yes	Yes
Chlorine Preparations	Somewhat	Yes	Yes
Peroxide or Peroxyacetic Acid	Yes	Yes	Yes
Phenolics	Yes	No	Yes
Glutaraldehyde	No	No	Yes

Due to differences in the composition of these three common transport buffers not all are compatible with all detection methodologies. For example, D/E broth is purple and can affect detection methods that require visual observation of a color change, such as Petrifilm or others. Additionally, the neutralizing agents themselves (e.g., aryl sulfonate complex) can have negative effects on some detection technologies.  

It is important to select the transport buffer that gives the broadest protection against the sanitizers most commonly used in the production process. Potential impacts on the selected detection method may need to be considered particularly if a change in transport buffer is implemented. Several buffers such as HiCap™ neutralizing buffer have been developed and optimized for use with both cultural and PCR based detection methods. 

 

EMP DATA INTERPRETATION & MANAGEMENT 

Types of Data 

• Qualitative – presence/absence of analyte (pathogen or allergen) on a surface. 
• Quantitative – population size of target microbes, level of ATP, or indicator count on a surface. 
• Limit of Detection (LOD)/Quantitation (LOQ) – minimum level of analyte that can be detected/quantified.  
  • LOD – for Salmonella, Listeria, or allergens detection is based on sample size (per swab, per sponge, per 25 g or cm²  sample, etc.). 
  • LOQ – for microbial populations, quantification also is based on sample size. 

What Do the Numbers Mean? 

• Presence/Absence of Salmonella, Listeria, or allergen. Typically reports as: 
  • Detected/Not Detected 
  • Positive/Negative 
  • Present/Absent 

Note: not detected, negative, or absent in a sample does not mean entire area is free of contamination. 

• Population size of target microbes; the number of bacteria counted in the sample. Expressed as colony forming units (CFU) per sponge or swab. 

Record Keeping 

• Sample Log - logbook or spreadsheet 
• Date and time of sampling 
• Name of person collecting the sample 
• Sample locations 
• Date submitted to laboratory 
• Results 
• Corrective actions (if needed) 

Establishment of Performance Targets 

Collect preliminary indicator counts for each location and determine a population level for each indicator to serve as a target level. For each indicator, also establish a population level that is unacceptable. 

Example Performance Targets 

Trend Tracking 

Trend tracking allows for big picture evaluation of a collection of data points over time to identify, with effective alert and action limits, early warning signs of process issues and excursions from alert and action limits. 

Establishment of an Action Plan 

If pathogen or allergen are found within Zone 1, the product that was produced along that surface may be considered adulterated. Therefore, timely action must be taken for the product and the process. 

The Action Plan should consider:  

• Product disposition if pathogen or allergen found near or on Zone 1 surface. Appropriate actions may include: 
  • Test and hold 
  • Reprocess (if kill step used) 
  • Destroy 
  • Divert
• Procedures to increase monitoring and vector swab around contamination site to find and eliminate source. Return to routine sample frequency after 3 successive negatives of the out-of-control site tested on 3 successive days. 

Forming a Response Team 

An OOS response team should include individuals knowledgeable and representative of each phase of the process. The team may include: 

• QA/QC personnel 
• Sanitation supervisor and crew 
• Production supervisor and crew 
• Maintenance supervisor and crew 

What to Do When Elevated Indicator Counts are Found? 

1. Break down and inspect equipment. 
2. Thoroughly clean and sanitize all equipment, surfaces, and tools in area. 
3. Resample areas where high counts were found. 
4. Re-clean, re-sanitize, and re-sample as needed. 
5. If high counts persist, implement corrective actions. 

Corrective Actions if Salmonella/Listeria monocytogenes is Found 

• Stop processing in the affected area. 
• Limit access to the area. 
• Break down and inspect equipment in the area. 
• Re-swab out-of-control area and surroundings to determine if contamination is localized or more widespread. 
• Clean and sanitize all equipment, surfaces, and tools in the area. 
• Conduct pre-operational inspection and re-swab. 
• Do not restart operations until all tests are negative. 
• Document corrective actions and consider creating a SOP to prevent recurrence. 
• Increase frequency of sampling from weekly to daily. 
• After 3 consecutive days of negative results, normal sampling may resume. 
• If the problem persists, consider removal, replacement, or redesign of contaminated equipment. 

  Routine Preventative Controls

• Control sources of water and air. 
• Repair structural damage and eliminate cracks and crevices that can harbor microbes. 
• Review and monitor GMPs. 
• Review and monitor SSOPs. 
• Audit production and maintenance practices. 
• Reinforce proper employee hygiene practices. 

 

This guide has intended to provide a high-level overview to considerations for any environmental monitoring program. However, the details and nuances of an environment are going to be specific to your individual process. Should you have additional questions, we are here to support.

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