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Sampling is the process of collecting and testing food, ingredients, the environment or other materials. Sampling is commonly used to monitor or verify the effectiveness of control measures put in place to prevent, eliminate or reduce to an acceptable level the hazards that present a risk of contamination to a food. Sampling can also provide assurance that incoming materials, finished products and water meet food safety standards.
It is important to collect food samples that are representative of a lot or a food contact surface being assessed. It is also important to ensure that samples are not compromised when being collected, stored or shipped, as this could lead to inaccurate results.
What is a sample
A collection of one or more units from a lot drawn for examination or testing purposes.
- food sample units could be entire packages of food, portions of packaged food, or portions of food being prepared
What is a random sample
A sample in which all the units were selected randomly by chance, such that each unit in the lot had the same probability of being chosen at any stage during the sampling process.
The Canadian Food Inspection Agency (CFIA) created this document as guidance to help food businesses comply with the Safe Food for Canadians Regulations.
It's your choice
You may use other guidance developed by provincial governments, industry associations, international partners or academic bodies as long as they can achieve the outcomes identified in the regulations. Always ensure that the guidance you choose is relevant for your particular business, product or products, and market requirements
This document provides information on the sampling process, including:
- Why sample
- What to sample
- What sampling plan to use
- Where to sample
- How to sample
- Storing and shipping samples
- Testing the samples
- What to do with sample results
Refer to the Further reading section for additional sources of information that may help you establish sampling procedures.
What's not included
While this document provides general guidance on sampling, it is not exhaustive – the reason for sampling and where the samples are taken will be unique for each business.
Roles and responsibilities
Food businesses are responsible for complying with the law. They demonstrate compliance by ensuring that the commodities and processes for which they are responsible meet regulatory requirements. If a written preventive control plan (PCP) is required, the food business develops a PCP with supporting documents, monitors and maintains evidence of its implementation, and verifies that all control measures are effective.
The CFIA verifies the compliance of a food business by conducting activities that include inspection, and surveillance. When non-compliance is identified, the CFIA takes appropriate compliance and enforcement actions.
1. Why sample
Sampling is commonly used to:
- assess the acceptance of consignments
- test for batch release
- control raw materials
- control in process products
- assess the finished product
- monitor, verify and validate the effectiveness of control measures, for example:
- determine whether control measures such as sanitation procedures are effective in preventing the contamination of a food
- determine whether the water used in your establishment meets potable water requirements
- monitor the pH or Aw level of a food at a critical control point to ensure that it is within the critical limits
- validate the shelf life established for the food
- assess the acceptability of an ingredient
Sampling is used to assess the presence and level of the following three types of hazards.
- Pathogens such as:
- Listeria, E. coli, Salmonella that are pathogens
- Micro-organisms that are indicators of unsanitary conditions such as:
- coliforms and generic E. coli
- Allergens such as peanuts, soy, eggs, milk, tree nuts, wheat, sesame, seafood, mustard, sulphites
- Drug residues such as antibiotics
- Pesticide residues such as Dichlorodiphenyltrichloroethane
- Toxins such as aflatoxins in peanuts, Paralytic shellfish poisoning and domoic acid in shellfish
- Extraneous materials such as glass or metal fragments
- Bone fragments
2. What to sample
The types of processes, treatment and food prepared in your establishment and the control measures applied will help determine the samples you should take.
The following are common types of samples taken in food production:
- finished food
- food in-line
- incoming ingredients
The surfaces in the area or environment where food is prepared are sampled to verify the effectiveness of cleaning and sanitation procedures. For example, samples of food contact surfaces are taken to test for:
- Adenosine triphosphate bioluminescent, an indicator of remaining food debris after cleaning.
- Remaining viable bacteria such as aerobic colony count or coliforms (after sanitizers are applied)
- Listeria spp. or L. monocytogenes to determine whether control measures put in place are effective
- The document Control measures for Listeria monocytogenes in ready-to-eat foods provides additional information you should consider
The food is sampled at the end of the production line, when it is packaged in its finished form, to verify that it meets specifications and is not contaminated.
Food in-line (during preparation)
Sampling food during preparation can help you assess its characteristics at a specific point in the process. It can also help you monitor critical limits to ensure they are met.
Water is commonly sampled to:
- assess the safety of the source water in the establishment
- verify the effectiveness of in-house water treatments such as UV, ozone and chlorine
- verify that the frequency at which recirculated water, used for processing and washing, is changed and the concentration of sanitizers used are adequate
For more information see the guidance document Water for use in the preparation of food.
Sampling incoming ingredients helps assess a supplier's food safety control measures.
3. What sampling plan to use
The sampling plan you select will depend on the reason for sampling. Statistically based sampling plans should be used when assessing final products. You can find information on sampling plans in the document General guidelines on sampling published by the Codex Alimentarius Commission
Information on sampling plans for microbiological analysis is also available in the document Microorganisms in foods 2: Sampling for microbiological analysis: Principles and specific applications published by the International Commission on Microbiological Specifications for Food.
4. Where to sample
Where to sample depends on what you are sampling and the reason you are sampling. The following provides examples of where different types of samples are taken based on what is being assessed.
The sites for collecting environmental samples are selected according to what information you are trying to gather. For example, your goal may be to assess the effectiveness of your sanitation procedures in an establishment; or your goal may be to monitor the microbiological state of the environment while food is being prepared. The following are examples of sampling sites:
- food contact processing equipment, such as tables and conveyors
- walls, floors, and drains in processing areas
- fluid piping systems
- vacuum and air blower systems
- refrigeration units
Sample sites can be grouped to obtain an assessment of common areas such as:
- food contact surfaces
- non-food contact surfaces
- raw ingredient handling areas
- finished product handling areas
Samples of a food in its finished state could be taken from a lot in storage to help assess its compliance.
Samples of food collected during preparation (to monitor characteristics such as temperature, pH or water activity) can be taken from the processing line at regular intervals (the beginning, middle and end of production).
Samples of ingredients can be taken when the ingredients are unloaded or in storage at the establishment - to help assess the effectiveness of a Supplier food safety assurance program
To help assess the quality of the water source, water samples should be taken:
- prior to its treatment or disinfection in the establishment
- at a point where no further treatment is performed (usually a tap or fixture in the processing area)
5. How to sample
It is important to practice proper sampling techniques to avoid contaminating samples and exposing yourself to contaminants.
- Wear protective items, such as gloves and protective clothing.
- Use only clean equipment and containers to take samples.
Samples should be labelled with the information you need to link the results back to the food, ingredient or food contact surface being assessed. Sample labels should include:
- date and time of collection
- description of what was sampled
- lot number
- sampling site
- name of the person who collected the sample
The sample units should be representative of the lot. For example:
- sample units are selected by chance using a random number generator
- sample units are selected at regular intervals, such as at the beginning, middle, and end of a production run
Collecting ingredient and food samples
When collecting samples:
- wash and dry hands prior to sampling
- use aseptic techniques when taking microbiological samples
- pre-packaged food samples should be collected in an original, unopened package
- use appropriate sampling containers that can withstand handling and shipping
- securely seal sample containers after filling so they cannot leak or become contaminated during further handling or transportation
- Note: Open, broken or damaged containers are not appropriate for sampling
Using aseptic techniques
When collecting samples for microbial testing avoid introducing microorganisms to the samples by following aseptic sampling procedures:
- Use only sterile equipment and containers, and properly re-sterilize sampling tools before using them again
- Make contact with the source material and the sample only with the sampling tool or the container
- Use sterile gloves if a sample must be touched with the hands. An aseptic sample should not be touched with bare hands
- Minimize exposure of the product, sampling equipment, and the interior of sampling containers to the environment. For example, avoid collecting samples in areas where dust or atmospheric conditions may contaminate the sample unless such contamination may be considered part of the sample
- Work rapidly. open sterile sampling containers only to insert the sample, and close them immediately
- Avoid unnecessary contact. The sample and sampling tool should not contact the interior, lip, or lid of the sterile container
Take care when opening and closing sample containers. It is easy to contaminate a sample during this step!
There are many things that you can do to reduce the risk of contaminating your sample. The following points are things to consider when sampling.
Opening sample containers
- For a bottle or cup: remove the cap or lid with a free hand and keep it in that hand during sample collection; only the exterior of the cap or lid can be touched
- For a bag: open the bag by using the tabs. Do not touch the opening of the bag
- Do not overfill the sampling container
Closing sample containers
- For a bottle or cup: replace the cap or lid on the container without touching the inside of the cap or the mouth of the bottle and secure the cap or lid
- For a bag: pull twist ties tight, whirl the bag three revolutions, and fold the twist ties towards each other to seal the bag
Collecting environmental samples
When collecting environmental samples you should wear sterile gloves.
The type of surface to be sampled and lab capabilities will determine the type of swab that should be used (for example, fabric-tipped swab, swatches, sponges, gauzes and clothes).
Source water samples
- Collect the sample from a source water outlet. Do not use a hydrant, hose, or any faucet located outside of building
- 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)
- Do not sample from a tap that is obviously contaminated
- Disinfect the end of the faucet with alcohol wipes or by flaming
- Run the cold water for at least two to three minutes
- Adjust the flow of the stream to ensure that no splashing occurs
- Use a sterile cup as your sampling container
- Securely seal sample containers after filling so they cannot leak or become contaminated during further handling or transportation
Recirculating, processing and wash water samples
- Collect the water using a sterile cup. If sampling from a spigot, flush it out well prior to taking sample
- Avoid contact between the cup and the equipment when taking the sample
- Securely seal sample containers after filling so they cannot leak or become contaminated during handling or transportation
6. Storing and shipping samples
Samples for microbial testing can be compromised by the temperature they are exposed to and the time that goes by before they are tested. To preserve their integrity you should store and ship the samples at appropriate temperatures and within the time frames recommended by the laboratory.
To prevent contamination, deterioration, and other damage that could compromise the integrity of a sample during transportation:
- before shipping, store samples in a manner to maintain their integrity
- measure and record temperature of sample units before placing them into the shipping container
- use sound, clean, dry shipping containers, coolers, coolant and packaging materials
- Pack samples tightly to prevent shifting
- transport frozen or refrigerated samples in an insulated shipping container of rigid construction and packed with suitable coolant material to maintain their frozen or refrigerated state. Avoiding direct contact with the coolant material
- ship samples collected as quickly as possible
7. Testing the samples
Samples taken to assess the compliance of a finished product should be tested at an accredited laboratory such as a laboratory accredited to the ISO/IEC 17025 standard General requirements for the competence of testing and calibration laboratories by the:
- Standards Council of Canada under the Program for Accreditation of Laboratories, in conformity with CAN-P-4D, or
- Canadian Association for Laboratory Accreditation
The test should be within the scope of accreditation for the laboratory.
A recognized test method should be used such as those outlined in Health Canada's Compendium of food allergen methodologies, Compendium of methods for chemical analysis of foods and Compendium of analytical methods.
In regards to marine biotoxins in shellfish, the test method used can be:
- an official method for which the laboratory has demonstrated that they are able to achieve the published method performance parameters
- another method that has been validated and meets Codex Alimentarius performance criteria for marine toxins
8. What to do with the results
Satisfactory results provide evidence that your control measures are effective. Unsatisfactory results however, indicate that your control measures are not effective. You are responsible for the safety of the foods you prepare and need to take action when you obtain results that indicate a food safety situation or that your control measures are not effective. It is important for you to follow up with the corrective actions that are identified in your PCP.
The following references contain information that helps explain food safety controls, demonstrates how to develop them, and provides examples. The CFIA is not responsible for the content of documents that are created by other government agencies or international sources.
- Corrective actions
- Conducting a hazard analysis
- Control measures for Listeria Monocytogenes in ready-to-eat food foods
- Monitoring procedures
- Verification procedures
- Canadian standards and guidelines for microbiological safety of foods (Volume 1 - The Compendium of Analytical Methods)
- Canadian maximum levels for chemical contaminants in foods
- Canadian maximum residue limits for pesticides
- Canadian maximum residue levels for veterinary drugs
- Codex Alimentarius, General guidelines on sampling, CAC/GL 50-2004
- Health Canada, Policy on Listeria monocytogenes in ready-to-eat foods, 2023
- International Commission on Microbiological Specifications for Food, Microorganisms in foods 2: Sampling for microbiological analysis: Principles and specific applications
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