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Operational guideline: General principles of sampling - food products, environment, water and ice

Requirements for the Safe Food for Canadians Regulations

Although the Safe Food for Canadians Regulations (SFCR) came into force on January 15, 2019, certain requirements may apply in 2020 and 2021 based on food commodity, type of activity and business size. For more information, refer to the SFCR timelines.

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1.0 Purpose

The purpose of this document is to provide Canadian Food Inspection Agency (CFIA) inspection staff with the general procedures for sampling food and food production environments, as well as water and ice that come into contact with food. This guidance is to ensure that such samples are representative of the food and the food production environment.

This document is intended to be used in conjunction with the Standard Inspection Procedures (SIP) and the Operational Guidelines for specific food commodities.

The guidance outlined below may be used when verifying compliance of a food product, to aid in assessment of a Preventive Control Plan (PCP) related sub-element, as part of a food safety investigation, or follow-up to a complaint.

Sampling frequencies and sample unit details are provided in the CFIA Sampling Information.

2.0 Authorities

The inspection powers, including the authorization to take samples, by the above legislation are identified and explained in the Operational guideline – Food regulatory response guidelines.

3.0 Reference documents

4.0 Definitions

Unless specified below, definitions are located in either the:

Aseptic technique
The methods used to take a clean specimen without cross contaminating the sample or the surrounding areas.
The consumer is the final user of a product. (a person or an institution, such as a hospital, hotel, organization or restaurant which purchases a product for its own use.)
Food contact surface
Any surface or object in the post-lethality processing environment that comes in contact with the food product.
A defined quantity of a commodity (including food animals and livestock carcasses) that has been produced or manufactured under the same basic conditions, and has identified under the same code. When there is no code identification in place at an establishment, a lot is either:
  • a quantity of product produced under the same conditions, on the same day, at the same establishment; or
  • a quantity of the same type of product from the same producer, available for sampling at a fixed location
Lot size
The lot size is the number of units of product in a lot.
Random sample
A random sample is one in which all elements in the lot have an equal and independent chance of being included in the sample.
A sample is a collection of one or more sample units selected from a lot or environment for inspection. The sample comprises all of the sample units drawn for examination or testing purposes from a particular lot.
Sampling plan
The sampling plan specifies the number of sample units required and criterias (acceptance and rejection) to make an accurate inspection decision on a lot.
Sample size (n)
Sampling size is the number of sample units comprising the total sample drawn from a lot or production.
Sample Unit
Sample unit is one of a number of individual containers, or a portion of a food or primary container examined or evaluated as a single unit.
Unit size
The particular food portion or container selected as a sample and from which one or more units will be taken for analysis.

5.0 Acronyms

Acronyms are spelled out the first time they are used in this document and are consolidated in the Food business line acronyms list.

6.0 Operational guideline

6.1 General principles

  1. Follow principles of good personal hygiene; inspectors must not be a source of contamination:
    1. Keep hands, fingernails, clothing, and shoes/boots thoroughly clean at each visit
    2. Removed personal effects and jewelry prior to collecting a sample
    3. Secure effects that cannot be removed (under clothes or gloves)
  2. Conduct sampling to maintain the integrity and continuity of the sample associated with the lot, from the time the sample is drawn to the completion of the inspection.
  3. Collect samples when the lot can be accessed without interference. If there are conditions that cause interference with sampling, document the issue and report the issue to the Inspection Supervisor.
  4. Begin the sampling sequence in the finished product area first (least contaminated) and proceed through the potentially contaminated areas, finishing at the raw materials and receiving areas.
  5. Conduct sample collection aseptically to avoid contaminating the sample, the product, the environment and the inspector.
  6. Label each sample unit with adequate information so that the unit can be matched to the sampling submission form. The markings must be legible and permanent.
  7. Employ a sample identification system that permits an inspector to:
    1. assign a unique identification number for the sample associated with a lot
    2. affix all pertinent information to the sample, and
    3. document all sampling information for record keeping purposes

6.2 Types of sampling plans

There are different types of sampling plans based on the design and the purpose of the sampling and testing, including monitoring, directed, compliance, and blitzes or special surveys. These terms are described in the Canadian Food Inspection Agency - Health Canada Food Sampling and Testing Terminology.

Legal sampling is a sanctioned method in which continuity and chain of custody are maintained. It is undertaken for specific conditions where legal action is the anticipated follow up action. Certain additional criteria are demanded during the sampling submission and laboratory testing of these samples. Legal advice should be sought prior to the initiation of such activities. (Refer to Appendix 1 for guidance on taking legal samples)

6.3 Food products sampling

6.3.1 Prepare for sampling

Prior to collecting samples, perform the following in-office steps:

  1. Plan sampling activities, whenever possible, so that samples are not stored or shipped over the weekend. In some cases, the laboratory will accept samples for analysis on the weekend. Contact the laboratory in advance to determine availability.
  2. Determine the intent of the sampling
    1. To support inspection findings,
    2. To fulfill the CFIA Annual Sampling Plan,
    3. To assess human exposure to food-related risks, etc.
  3. Prepare the Inspector toolkit and additional materials or protective equipment required. Sampling equipment/materials are selected as appropriate for the collection, preparation, storage and transportation samples and for maintaining the condition of the samples. Refer to Inspector toolkit (internal access only – RDIMS 11289973) for the list of equipment that may be required for sampling. If visiting multiple facilities in one day, respect biosecurity and obtain sufficient supplies for each site. Follow appropriate biosecurity measures for preparation, cleaning and sanitizing equipment, prior to arriving at the regulated party's premises. (Refer to the SIP Appendix I for Biosecurity)
  4. Acquire or assign an appropriate series of laboratory sample numbers to be used to uniquely identify the samples. Refer to the CFIA Sampling Information (internal access only) for guidance on lab sample numbers and how to proceed if additional samples per sampling plan are required and for special request sampling procedures.

6.3.2 Determine which food products to sample

Choose a product to sample by considering the following factors:

6.3.3 Locate and identify the lot

Lots are typically differentiated by logical breaks in production (such as different source of honey), but should be limited to a single production day or less.

Each lot should be prepared for sampling in such a way that the sample(s) can be taken without hindrance. If a portion of the lot has already been distributed, the remaining quantity of the lot is to be considered the sampling lot.

Obtain the following information, where applicable:

6.3.4 Define the sample unit

Sample Units may consist of:

When a lot consists of pre-packaged product, each package constitutes a sample unit.

If the container sizes available for sampling differ from the sample size required, adjust the number of sample units accordingly. For example, if the required sample size is 1 unit (500 g) but only 250 g containers are available, two containers will be required from the same lot to meet the 500 g sample size requirement. Conversely, if only larger containers are available, the entire container can be sampled or a 500 g sample can be drawn. If the required sample size requires a number of sub samples, for example 6 units x 250 g, 6 units of different containers must be taken regardless of container size.

6.3.5 Sample collection

6.3.6 Identify and document the sample unit

Record the details of sampling, for example, lot location, no. of samples drawn, unique identification number, time of sampling, codes drawn

Ensure all samples are accompanied by a completed food product sampling submission form in the LSTS application. Include the following information if available and where appropriate:

Include any other relevant information which would assist in performing the analysis or assessing the results, such as:

6.4 Environmental sampling

Environmental sampling for the detection of microorganisms is employed to determine the presence of pathogens or other organisms on equipment and food contact surfaces. The detection of microorganisms may indicate poor sanitation or microbial growth niches in a food establishment. Environmental sampling consists of Food Contact Surface (FCS) and Non Food Contact Surface (NFCS) sampling.

The sampling technique chosen will depend on type of area to be sampled. For example, swabbing is better for material sampling, while exposure of agar is well suited for ambient air sampling. Details on different sampling techniques are found in Appendix 6.

6.4.1 Prepare for sampling

Take the following steps prior to sampling:

  1. Obtain a copy of the establishment's environmental sampling program
  2. Acquire a process flow chart, including the employee and product traffic patterns
  3. Identify sampling sites and target microorganisms or hazards. Sampling sites may include walls, floors, drains, equipment, food contact surfaces, etc.
  4. To assess cleaning and sanitation conditions in the facility, plan to take environmental samples immediately after cleaning and sanitation, but before production starts
  5. To assess microbiological conditions during production, plan to take samples during production, typically 3 hours after start of operation or at the mid-time production when production is less than 3 hours
  6. To assess the adequacy of the hazard analysis
    • for lines producing ready-to-eat (RTE) products subjected to a heat process treatment, plan sampling to start at the post-lethality step
    • for lines producing RTE products not subject to a heat treatment process, plan to take samples at the step where the product is in its final RTE form. For example, for cold-smoked fish, sampling should start at the cold smoking step; for sushi, sampling should start at the step where all the ingredients are assembled as sushi.
  7. Identify the line(s) with higher risk and select the collection sites (food contact surfaces only) in the post-lethality treatment areas of the establishment with the highest probability of contamination.
  8. Assemble the Inspection Toolkit, including sufficient number of swab kits

6.4.2 Selection of food contact surface (FCS) sample sites

  1. Prior to starting sampling, survey the processing line to determine sites to be sampled.
  2. Select sites that are exposed to both the environment and the product or where there is a higher probability of RTE product contamination and the greatest potential to affect the safety of the final product. Suggested food contact surface are:
    • Slicers, dicers, shredders, etc.
    • Carts/racks
    • Cheese molds
    • Blades of slicers
    • Packaging tables, conveyor belts
    • Scales(used to weigh RTE products before it is packaged)
    • Cutting tables
    • Utensils (knives, trays)
    • Packaging equipment (vacuum packaging, etc.), packaging material
    • Employee gloves/hands, aprons.
      • note that it is recommended to swab at random at least two employees that work in the plan if these sites are selected
  3. Select 1 specific line. Give priority to the line most at risk, such as those packaging the highest risk cheeses in category 1, or to shredding, slicing and dicing operations where the risk of post-processing contamination is higher
  4. Determine which environmental sampling method (refer to Appendix 6) will be most effective for the chosen swabbing sites
  5. Ideally, 10 FCS sites should be selected (minimum of 5 FCS). The number of sampling sites will vary according to the complexity of processing system or packaging line
  6. Surfaces are to be swabbed after the start of the operations, like 2-3 hrs into processing is recommended

6.4.3 Dried or accumulated material sampling

In addition to surface sampling, there may be evidence of dried or accumulated materials on processing lines. The sample size of such material will be determined by the analysis required and/or the amount of sample available.

  1. Select the environmental site for sampling
  2. Determine what sterile materials/tools will be needed to collect the sample, for example scraper, sweeper, tongs, forceps, spoons, etc.
  3. Wash and dry hands
  4. Put on sterile gloves
  5. Aseptically remove the sample using sterile tools and place it into a sterile bag or sterilized bottle/container
  6. The sample should be well marked, for example site location, conditions, etc.
  7. When collecting environmental samples from inside large equipment (for example milk drier), dress entirely in sterile clothing (such as head cover, facial hair cover, disposable overalls and overshoes, etc.)
  8. Change sterile tools (such as forceps, etc.) and gloves after each environmental sample is collected

6.5 Water and ice sampling

Water samples are taken in order to evaluate the quality of the water source and the characteristics of water used as an ingredient and/or in treatments/cleaning.

Quantity and size of the unit sample are indicated in the sampling plan and are established according to the type of analysis done in laboratory.

6.5.1 General principles related to water sampling

6.5.2 Running water source

Collect the sample from a source water outlet within the facility. Do not use a hydrant, hose or any faucet located outside of building. Do not sample from a tap that is obviously contaminated.

  1. Request the establishment to remove any aerators or other devices from the outlet to be sampled. These devices may be heavily contaminated and may alter the water sample result
  2. Disinfect the end of the faucet with alcohol wipes
  3. Run the cold water for at least two to three minutes
  4. Adjust the flow of the stream to ensure that no splashing occurs
  5. Fill the container to the fill line or within 6-7 mm (1/4 inch) of the top. The sampling container should not be overfilled. If the sampling container is accidentally overfilled, discard the container and use a new sampling container.

6.5.3 Ice

A sample, consisting of ten sample units drawn at random from each lot, shall be taken. Each sample unit shall consist of at least 100 ml or g. Collect original unopened container wherever possible. Place each collected sample unit into a separate sterile container. Do not allow sample units of prepackaged ice to thaw during shipment.

6.6 Transportation and storage

Samples should be kept in such a manner that the controlled characteristic is not modified. For example, use of a sterile and cooled container is mandatory for samples that will be analysed for microbiological control.

Transport samples in clean and dry containers offering adequate protection from external contamination and protection against damage to the sample in transit. Refrigerated or frozen samples should be transported in insulated containers with a sufficient quantity of ice packs or dry ice to maintain sample integrity and the same conditions at which they were sampled.

If samples are not shipped immediately, store them in a secure location in the office. Keep frozen samples in a freezer (-18°C), refrigerated samples at an appropriate temperature (0 to 4 °C) and products which do not require refrigeration storage conditions at ambient room temperature.

6.7 Shipping

  1. Contact the laboratory to make arrangements with the receiving person prior to shipping the sample
  2. Choose shipping coolers and containers that are appropriate for your sample size, the number of samples being sent and are dry, leak-proof and sealable
  3. For samples that require temperature control to ensure sample integrity, measure the temperature of the sample prior to packaging the sample units into the shipping container and record it on the sample submission form
  4. Complete LSTS sample submission form and insert in a plastic bag to protect it from being damaged, leave it inside the shipping cooler/container
  5. Pack samples tightly to prevent shifting within the shipping container but not so tight that the samples may be compromised during transport. To properly secure samples, use clean, dry, shredded paper, styrofoam nuggets, bubble wrap, or other suitable packaging material. Place each glass jar/ bottle in a separate bag to prevent injury and damage in case of broken glass.
  6. Pack sufficient amount of coolant material, like ice packs, to ensure samples maintain proper temperature through to arrival at the laboratory
    1. refrigerated samples should maintain a temperature not less than 0 °C and not more 7 °C
    2. frozen products should not exceed 0 °C
    3. environmental samples should not be less than 0 °C or greater than 10 °C
  7. Coolant material must not directly touch the samples. Use a layer of packaging material to avoid direct contact between the samples and the coolant material in order to prevent freezing.
  8. For very large coolers it may be necessary to place ice packs around the sides of the cooler or in between samples to ensure consistent and adequate temperature.
  9. During warmer months, place empty shipping containers in a freezer long enough to chill them thoroughly prior to use. Additional ice packs may be required to maintain proper temperature during periods of hot weather.
  10. When dry ice is used to ship frozen samples, avoid direct contact with the samples. Use sufficient dry ice to keep the product frozen. Guidance on how to use dry ice can be found in document Shipping Foods with Dry Ice
  11. Do not ship different analytical product/sample types in the same shipping cooler/container.
  12. If more than one shipping container is required (due to sample size/weight), clearly indicate the container number and total number of containers on each box/cooler, courier waybill, and LSTS form
  13. Before sealing the transport container, be sure that all completed submission documents are included. A copy of the LSTS form should be placed in each container. Pack LSTS submission forms in a plastic bag to protect them from moisture.
  14. Tightly close and secure the transport coolers/containers.
  15. Ensure perishable samples are properly marked for handling by the carrier
  16. Address the shipment to the appropriate lab personnel and include a contact phone number if possible.
  17. After the samples have been picked up by the shipper, contact the lab to advise them that the samples are now in transit.
  18. Advise the laboratory of the estimated arrival time of the sample and the carrier information. If the inspector is not able to contact the laboratory or if the microbiology sample delivery cannot be completed within 24 hours, he/she should consider the merits of sampling at another time.

6.8 Results - analysis and interpretation

The LSTS will generate one of four possible sample test result outcomes: Satisfactory (S), Unsatisfactory (U), Investigative (I) and No Decision (ND). It is important to remember that the sample assessment is not directly related to compliance.

6.8.1 Samples judged Investigative (I) or Unsatisfactory (U)

When a sample is judged investigative or unsatisfactory, evaluate the results and determine if there is a violation and/or a potential health and safety concern with respect to product on the market. Consult the Standard Regulatory Response Procedure, and any Food or Commodity specific guidance to help identify any regulatory response options and strategies. If additional guidance is required, consult other personnel such as the Recall Coordinator, the Inspection Supervisor or Inspection Manager (IM) or designate, and others as appropriate for resolution of the issue. The degree of consultation may vary depending upon the issue, from notification by e-mail to conference calls and meetings.

If product has left control of the regulated party, a food safety investigation may be required to ensure all aspects of the potential health and safety issue are addressed. Follow the guidance in the Food Safety Investigation Response.

When a potential health and safety issue is identified, initiate the regulatory response process to limit the exposure to the potential health risk or to prevent further violation(s) of the SFCA and SFCR, the FDA and the FDR.

When a potential health and safety issue is not identified or a recall is not warranted other regulatory response actions may be required to address investigative or unsatisfactory sample results.

6.8.2 Samples judged Satisfactory (S)

The establishment should be notified, however, no further action is required. External LSTS Reports of Analysis (ROA) may be provided to regulated party if requested.

6.8.3 Samples Judged as No Decision (ND)

For samples judged as no decision, discuss the results with the Supervisor / Regional Program Officer or designate who will review as necessary.

7.0 Appendices

For general inquiries related to this Operational Guidance Document, please follow established communication channels, including submitting an electronic Request for Action Form (e-RAF) - (internal access only).

Appendix 1 - Legal sampling procedure

An inspector may perform legal sampling when it is anticipated that legal action is anticipated. Legal sampling demands more complex procedures for sample collection, submission and laboratory testing compared to routine product sampling.

In order to ensure that testing results are admissible in court, legal sampling procedures, as directed in FDR subsection A.01.050, must be strictly followed. Inspectors should consult with the Inspection Supervisor to determine if it is necessary to seek legal advice and consult with CFIA Enforcement and Investigation Services (EIS) prior to initiating legal sampling. It is important to let the laboratory contact know when the samples will arrive, the number of samples that will be shipped, and the analyses to be performed.

Laboratory contact information

Consult the appropriate laboratory contact prior to taking legal samples, to ensure that the laboratory is able to handle the samples.

Sample number and size

Consult with the Inspection Supervisor prior to taking legal samples. Generally, for extraneous material testing, select 24 individual containers with a minimum of 250 gram (g) or mL (milliliter) per container. For all other analyses, select 5 sub-samples with a minimum of 250 g or mL per sub-sample.

Obtaining the sample

Refer to FDR Subsection A.01.050 for complete details on sampling requirements. When taking a sample of an article pursuant to paragraph 23(1)(a) of the FDA, an inspector must inform the owner thereof or the person from whom the sample is being obtained of the inspector’s intention to submit the sample or a part thereof to an analyst for analysis or examination, and

  1. Where, in the opinion of the inspector, division of the product to be sampled would not interfere with analysis or examination, obtain a sufficient quantity of product for a triplicate sample and
    1. divide the quantity into three parts,
    2. identify the three parts as the owner's portion, the sample, and the duplicate sample and where only one part bears the label, that part shall be identified as the sample,
    3. seal each part in such a manner that it cannot be opened without breaking the seal, and
    4. deliver the part identified as the owner's portion to the owner or the person from whom the sample was obtained and forward the sample and the duplicate sample to an analyst for analysis or examination.
  2. Where, in the opinion of the inspector, division of the procured quantity would interfere with analysis or examination
    1. identify the entire quantity as the sample,
    2. seal the sample in such a manner that it cannot be opened without breaking the seal, and
    3. forward the sample to an analyst for analysis or examination.

Always choose sub-samples randomly from the same lot. At no time should a company representative choose the samples.

Sample identification

Write the sample number on all containers/packages of samples submitted to the laboratory. Avoid obscuring portions of the labels that are significant, such as the list of ingredients, label claim statements, product and brand name, lot code, etc.




Complete the sample submission form and include a signed copy of the form in the shipping box.

The Chain of Custody form (CFIA/ACIA 5428 internal access only) must be completed and should be attached to the outside of the shipping box (to facilitate the signing of the form upon sample transfer).

Refer to the Enforcement and Investigation Services (EIS) document: Evidentiary Consideration for Samples for further information.

Appendix 2 – Sampling for chemical analysis

Sample units chosen for chemical analysis should not undergo any adulteration (such as rinsing with water) which may change the chemistry results.

Please refer to General Sampling Instructions - Sampling Foods for Chemical Surveillance Programs.

Categories of chemical analysis

Additives and components analysis

Additives are chemicals added to the product during processing in order to preserve it in some manner, modify the colour, modify the taste, or alter the characteristics of the product. The application methods for these substances may vary which affects the distribution of the substance in the product. Substances included in this category are sulphite (bleaching agent), benzoate (preservative), nitrite, saccharin (sweetener), etc.

Components analyses are used to assess and express the nutritional value of a food. To determine compositional parameters in a food product, the amount (concentration, percentage) of ingredients, components and nutrients such as fat, protein, sodium, sugars, moisture, etc. are analysed

Product safety parameters and drug residue

Product safety parameters are those parameters which are used to curtail bacterial growth in a product and prolong the product shelf life. The parameters may be used in combination in a product or only one parameter may be controlled to prevent bacterial growth. Salt, water activity, and pH are included in this category.

Drug residue is residue that has resulted from the application of antibiotics or similar substances to animals (cattle, fish, bees, etc.) to prevent or treat disease. Tetracyclines, sulfonamides, and chloramphenicol are included in this category.

Chemical contaminants

Chemical contaminants are substances which are present in the food products as a result of the environmental conditions to which the food was exposed (for example allergens, sanitizer etc.). Organic contaminants concentrate in the lipid portion of the food whereas inorganic contaminants are more uniformly distributed throughout the muscle (protein) tissue or aquous portion of food (for example lead and paraformaldehyde, mercury, etc.)

Chemical indicators

Chemical indicators are substances which are produced from decomposition processes that are occurring in the food. Chemical testing is often used to corroborate results from sensory analysis. Quality indices include histamine, indole, and total volatile base nitrogen (TVBN), patuline in apple juice, peroxide value, etc.

Appendix 3 - Sampling for microbiological analysis

All samples must accurately reflect microbiological conditions at the time that sampling is performed. To maintain sample integrity, follow the procedures listed below.

Appendix 4 - Sampling for extraneous material

Extraneous material can include many different types of materials. Materials that can be harmful because of their hardness, sharpness, size or shape are of particular concern. Examples of harmful extraneous materials include glass, wood-chips, insulation, metal, or sharp plastic greater than 2 mm in size.

To help determine if the extraneous material is hazardous, background information should be gathered on the type of material used in the facility, facility maintenance history, consumer complaints and evidence of possible tampering.

When consumer complaints or inspection evidence indicates contamination by potentially harmful extraneous material, the product may need to be detained and directed samples taken. Laboratory consultation is also recommended. See document Guidelines for the General Cleanliness of Food – Extraneous Material Overview for more information on risk assessment and acceptance sampling plan parameters.

Appendix 5 - Sampling for radiation analysis

Irradiation is regulated under FDR Division 26. Industry may make submissions to Health Canada to allow new uses of food irradiation. Health Canada will permit new uses of food irradiation only after a safety assessment, and only listed items may be irradiated.

The current list of foods that are permitted to be irradiated is found on the CFIA external website: Irradiated Foods.

Food may be exposed to ionizing radiation for a variety of purposes, including:

Appendix 6 - Environmental sampling methods

Surface contact sampling: Swab method

This method is used to sample any surface up to 1 meter squared (m2). When collecting environmental samples from inside large equipment (for example, milk drier), dress entirely in sterile clothing (such as head cover, facial hair cover, disposable overalls and overshoes). Ideally, a 900 cm2 (30 x30 cm or equivalent) surface should be swabbed whenever possible.

  1. Wash and dry hands
  2. Aseptically open a sterile container (jar or bag) containing the pre-moistened sterile swab (Note: Each container should only have one sterile pre-moistened swab, cloth or sponge)
  3. Put on sterile gloves
  4. Aseptically remove the pre-moistened sterile swab from the container using sterile gloves or tongs
  5. Swab walls and floors (1 m2) using pre-moistened sterile swab
  6. Swab small food contact surfaces (100 cm2) using fabric-tipped swabs or sponges.
  7. Rub the swab firmly and thoroughly over the surface to be sampled, without lifting the swab, swab the surface area up and down until the whole target surface is covered, (see Figure A) then turnover the swab and swab the surface area from right to left until the whole target surface is covered. (see Figure B)
    Figure A: Up and down motion.
    Figure A: Up and down motion.
    Figure B: Right to left motion
    Figure B: Right to left motion


    Where the food contact surface being swabbed is cracked or has pre-drilled holes – focus swabbing on these cracks/ crevices to target potential bacterial niches.

    For surfaces which are difficult to swab because of their contour (such as conveyor belts), it may not be possible to swab a defined area using the mentioned procedure. In this case, swab the area to be sampled using the same described technique (up and down/ left to right) and then turn over the swab once again and swab the surface area in a diagonal pattern. This allows the sampling of every plane of the surface that will likely come into contact with the food (see Figure C)

    Figure C: Swabbing of irregular surfaces – Up and down/right to left and diagonal motions.
    Figure C: Swabbing of irregular surfaces – Up and down/right to left and diagonal motions.
  8. Release the swab into the appropriately labelled sample bag. Do not let the swab touch the outside of the bag
  9. Seal the bag, making sure not to contaminate the sample
  10. Place the bag in the Styrofoam box
  11. Sanitize the sample site using a 70% ethanol spray solution following environmental swabbing (note that some establishments might want to perform their own sanitation after CFIA swabbing)
  12. Change sterile forceps and/or gloves after each environmental sample is collected.
  13. The sample should be well marked, for example site location, conditions, etc.
  14. Place the sample into your carry bag/ice packed cooler

Surface contact sampling: Replicate Organism Direct Agar Contact (RODAC) plate method (for flat impervious surfaces)

  1. Wash and dry hands
  2. While wearing sterile gloves, open the bag containing the RODAC plates and only remove the plate that will be used.
  3. Remove the plastic cover and carefully press the agar surface to the surface being sampled.
  4. Apply uniform pressure on the back of the plate so that the entire agar surface contacts the area being sampled.
  5. Remove the RODAC plate from the surface being sampled and replace the cover onto the RODAC plate.
  6. Repeat the previous steps until all environmental surfaces are sampled using a new RODAC plate each time
  7. Immediately label each RODAC plate with adequate information so that the plate can be matched to the sampling submission form. The markings must be legible and permanent.
  8. Stack the plates (like 5 - 10) on top of each other and secure them with masking tape
  9. Put the piled RODAC plates in sample bags or other suitable containers
  10. Seal bag tightly
  11. The sample should be well marked, for example site location, conditions, etc.
  12. Place the sample into your carry bag/ice packed cooler
  13. Wipe off the surface that was sampled with a sterile wet cloth or sanitizer (such as 70% ethanol)

Surface contact sampling: Petrifilm™ method (used for sampling irregular surfaces)

  1. Wash and dry hands
  2. Put on sterile gloves and open the bag containing the Petrifilm™ plates
  3. Remove as many plates as required, and hydrate them following the manufacturer's instructions
  4. Peel back the top film of the Petrifilm™ (gel will adhere to top film) Note: On occasion the gel may split (adhering to both the top and bottom of the Petrifilm™ when the top film is lifted). This splitting of the gel will not affect the performance of the product
  5. Contact the top film of the gel, not the bottom, to the surface being tested
    Note: Avoid touching the growth area and bottom cardboard of the Petrifilm™ plate with any surface, including your hands, that is not being sampled
  6. Firmly rub fingers over the entire film side of the gelled area of the Petrifilm™ to ensure good contact with surface
  7. Lift the film from surface and rejoin the top and bottom sheets of the Petrifilm™
  8. Before going to the next sampling site, wipe off the surface that was sampled with a sterile wet cloth or sanitizer (such as 70% ethanol)
  9. Label each Petrifilm™ plate with adequate information so that the plate can be matched to the sampling submission form. The markings must be legible and permanent
  10. Put the Petrifilm™ plates in a sterile sampling bag and handle with care
  11. Place the sample into the carry bag/ice packed cooler

Appendix 7 - Random sampling procedure

A true random selection of pallets and the selection of individual packages from each case can be achieved by using a serial number system and random number tables or a device such as a statistics calculator or computer with random number generation capabilities.

The random selection of cases from the pallets can be conducted by using a lot numbering system and a random number generator.

1.0 Numbering systems: Serial and three-dimensional lot numbering

A numbering system for the lot must be decided upon before obtaining the random numbers for the sample. Two methods of numbering a lot are "serial lot numbering", and "three-dimensional numbering".

1.1 Serial lot numbering

In a simple arrangement, such as packages on a shelf or on a packing line, the packages in the lot can be considered to be numbered from 1 to n, where "n" is the total number of packages. The inspector does not have to mark the packages with numbers, but each package should have a number assigned to it by memory. The packages may be arranged in some order to clarify the numbering system in the inspector's mind. A simple sketch on a piece of paper may also be useful.

If the packages are in only one layer, they may be found or arranged in rows and columns on the shelf. Imagine that the packages are numbered from 1 to 15 in some systematic fashion, as illustrated below:

Figure D: An example of a single layer of packages with n = 15, arranged in columns and rows for ease of numbering.
Figure D: An example of a single layer of packages with n = 15, arranged in columns and rows for ease of numbering.

If there is more than one layer of packages, extend the serial numbering system layer by layer. In this example, the second layer would be considered to be packages numbered 16 through 30, the third layer, packages numbered 31 through 45, the fourth numbered 46 through 60, and so on, as illustrated below:

Figure E: An example of the serial numbering system where n = 60 and packages are arranged in colums, rows and layers for ease of numbering.
Figure E: An example of the serial numbering system where n = 60 and packages are arranged in colums, rows and layers for ease of numbering.

The inspector may use any numbering scheme as long as each of the packages has a number associated with it. In the 4-layer system previously mentioned, where the total number of packages equals 60, package number 39 would be in the third layer from the bottom, second row from the front, fourth package from the left. In this example, the package is shaded and the number is in bold.

Obtaining random numbers for the sample

Once all of the packages in the lot have been assigned numbers (from 1 to n), it is necessary to obtain random numbers corresponding to the total number of required sample units as follows:

  1. if the lot contains 100 packages or less, use 2-digit random numbers (note "00" is the 100th package)
  2. if the lot consists of more than 100, but not more than 1000 packages, use 3-digit random numbers (note "000" is the 1,000th package)
  3. using a random number generator (such as random sample number table, statistics calculator, or computer), record random numbers which are less than or equal to the total number of packages in the lot
  4. continue to record random numbers until you have enough for the amount of samples you need to take
  5. rearrange the random numbers in ascending order to facilitate sample selection

For example, 5 sample units are to be collected from a lot consisting of 60 packages. Using the two-digit random sampling number table provided starting at the first number, on the top left-hand corner of the following table, and going from top to bottom, the following random numbers are recorded: 20, 22, 45, 44, 16. Sample units corresponding to the above random numbers should be collected.

1.2 Three-dimensional lot numbering

When a large stack of packages or cases must be numbered, the inspector can use a three-dimensional lot numbering system using the Right, Up and to the Back method, referred to as "RUB".

Obtaining random numbers for the sample
  1. Choose the lower left corner of the stack as a "zero point" or starting place.
  2. Record the number of packages in the lot for each of the three directions (RIGHT, UP and BACK). For example, in Figure 2, there are 5 packages RIGHT, 4 packages UP and 3 packages BACK (5 x 4 x 3). At the bottom of the table in the spaces labelled "Dimensions of Stack," record the total number of units in each direction in the stack. (This will aid in using the random numbers generated because numbers larger than this are unusable).
  3. Using the two digit random sampling number table provided below, begin generating random numbers by using every random number less than or equal to the dimension shown at the bottom of the worksheet and record those random numbers in the second column "Right" of the worksheet.
  4. When the second column of the work sheet is completed, fill in the third column "Up" and then the fourth column "Back" using the same method.
  5. If all the dimensions of the stack are 10 or less, use one of the digits of the random numbers found in the random sample number table. If any one of the dimensions is greater than 10 but not greater than 100, use a two digit random sample number table to generate the random numbers. If any dimension is greater than 100 but not greater than 1000, use a three digit random sample number table.

For example, the dimensions of the stacked packages are 5 x 4 x 3 (60 packages). Below is a "Package Selection Worksheet" illustrating the 5 required sample units. The first sample package is 2 packages to the Right, 3 packages Up, and 3 packages Back from the starting point. The fifth sample package is 1 package to the Right, 2 packages Up, and 1 package Back from the starting point.

Package Selection Worksheet
Samples required Package location Right Package location Up Package location Back Corresponding package # (Figure 2)
Sample #1 2 3 3 42
Sample #2 2 2 1 22
Sample #3 4 4 3 59
Sample #4 4 4 1 54
Sample #5 1 2 1 21
(Continue if a larger sample size is required)
Dimensions of Stack 5 4 3 60
Example of a Two-digit random sampling number table
first digit second digit third digit four digit five digit six digit seven digit eight digit nine digit ten digit eleven digit twelve digit thirteen digit fourteen digit fifteen digit sixteen digit seventeen digit eighteen digit nineteen digit twenty digit
20 17 42 28 23 17 59 66 38 61 02 10 86 10 51 55 92 52 44 25
74 49 04 49 03 04 10 33 53 70 11 54 48 63 94 60 94 49 57 38
94 70 49 31 38 67 23 42 29 65 40 88 78 71 37 18 48 64 06 51
22 15 78 15 69 84 35 52 32 54 15 12 54 02 01 37 38 37 12 93
93 29 12 18 27 30 30 55 91 87 50 57 58 51 49 36 12 53 96 40
45 04 77 97 36 14 99 45 52 95 69 85 03 83 51 87 85 56 22 37
44 91 99 49 89 39 94 60 48 49 06 77 64 72 59 26 08 51 25 57
16 23 91 02 19 96 47 59 89 65 27 84 30 92 63 37 26 24 23 66
04 50 65 04 65 65 82 42 70 51 55 04 61 47 88 83 99 34 82 37
32 70 17 72 03 61 66 26 24 71 22 77 88 33 17 78 08 92 73 49
03 64 59 07 42 95 81 39 06 41 20 81 92 34 51 90 39 08 21 42
62 49 00 90 67 86 93 48 31 83 19 07 67 68 49 03 27 47 52 03
61 00 95 86 98 36 14 03 48 88 51 07 33 40 06 86 33 76 68 57
89 03 90 49 28 74 21 04 09 96 60 45 22 03 52 80 01 79 33 81
01 72 33 85 52 40 60 07 06 71 89 27 14 29 55 24 85 79 31 96
27 56 49 79 34 34 32 22 60 53 91 17 33 26 44 70 93 14 99 70
49 05 74 48 10 55 35 25 24 28 20 22 35 66 66 34 26 35 91 23
49 74 37 25 97 26 33 94 42 23 01 28 59 58 92 69 03 66 73 82
20 26 22 43 88 08 18 85 08 12 47 65 65 63 56 07 97 85 56 79
48 87 77 96 43 39 76 93 08 79 22 18 54 55 93 75 97 26 90 77
08 72 87 46 75 73 00 11 27 07 5 20 30 85 22 21 04 67 19 13
95 97 98 62 17 27 31 42 64 71 46 22 32 75 19 32 20 99 94 85
37 99 57 31 70 40 46 55 46 12 24 32 36 74 69 20 72 10 95 93
05 79 58 37 85 33 75 18 88 71 23 44 54 28 00 48 96 23 66 45
55 85 63 42 00 79 91 22 29 01 41 39 51 40 36 65 26 11 78 32
67 28 96 25 68 36 24 72 03 85 49 24 05 69 64 86 08 19 91 21
85 86 94 78 32 59 51 82 86 43 73 84 45 60 89 57 06 87 08 15
40 10 60 09 05 88 78 44 63 13 58 25 37 11 17 47 75 62 52 21
94 55 89 48 90 80 77 80 26 89 87 44 23 74 66 20 20 19 26 52
11 63 77 77 23 20 33 62 62 19 29 03 94 15 56 37 14 09 47 16
64 00 26 04 54 55 38 57 94 62 68 40 26 04 24 25 03 61 01 20
50 94 13 23 78 41 60 58 10 60 88 46 30 21 45 98 70 96 36 89
66 98 37 96 44 13 45 05 34 59 75 85 48 97 27 19 17 85 48 51
66 91 42 83 60 77 90 91 60 90 79 62 57 66 72 28 08 70 96 03
33 58 12 18 02 07 19 40 21 29 39 45 90 42 58 84 85 43 95 67
52 49 40 16 72 40 73 05 50 90 02 04 98 24 05 30 27 25 20 88
74 98 93 99 78 30 79 47 96 92 45 58 40 37 89 76 84 41 74 68
50 26 54 30 01 88 69 57 54 45 69 88 23 21 05 69 93 44 05 32
49 46 61 89 33 79 96 84 28 34 19 35 28 73 39 59 56 34 97 07
16 65 13 44 78 39 73 88 62 03 36 00 25 96 86 76 67 90 21 68
64 17 47 67 87 59 81 40 72 61 14 10 28 28 55 86 23 38 16 15
18 43 97 37 68 97 56 56 57 95 01 88 11 89 48 07 42 60 11 92
65 58 60 87 51 09 96 61 15 53 66 81 66 88 44 75 37 01 28 88
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