SOP: Collection and Transportation of Samples

GIFSQ — Global Institute for Food Safety & Quality

1. Principle

Reliable microbiological results start before analysis: the sample taken from the lot must represent the lot, and it must reach the laboratory in the same state the consumer met it. This procedure covers how to collect sample units from a lot and how to transport them so that the microflora does not change on the way to the bench. It applies to all methods that detect bacteria in food, food ingredients and environmental samples.

2. Apparatus required

• Sterile sample containers (for sample units collected from bulk or loose product)
• Refrigeration or freezer equipment for transport (cooler, gel packs or freezer as needed)

3. Procedure

Take a sample from the lot, made up of the specified number of sample units — usually between 5 and 60 — drawn at random from each lot

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Make each sample unit at least 100 mL or g, unless the method or the specific commodity sampling plan stipulates otherwise

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Collect the original unopened container wherever possible

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For bulk product: collect several sample units from one container, but do not collect the total number of sample units from one container. More than one sample unit may also be taken from large institutional or bulk containers when the number of sample units required exceeds the number of containers in the lot. Place the collected sample units in sterile containers. A sample unit consists of more than one container when the lot is made up of containers smaller than the minimum requested size — for example four 25 mL or g containers in each sample unit

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Use aseptic techniques when collecting the sample units

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Keep each sample unit refrigerated or frozen during transport, depending on the nature of the product. Shelf-stable products may be transported at room temperature. Fresh fruits and vegetables are often sold at ambient temperatures in public markets, but they should be sent at refrigeration temperatures to keep the microflora as close as possible to the state of the sample presented to the consumer at the time of purchase (avoiding overgrowth of mesophiles that may hinder detection of the targeted pathogen)

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Do not let sample units that are usually frozen thaw during shipment. If frozen products do thaw, do not re-freeze them; analyze them immediately if they arrive at a suitable temperature, for example between 0 and 7 °C

4. Precautions

• Never re-freeze a frozen sample unit that has thawed during transport
• Keep refrigerated sample units cold enough that mesophile overgrowth does not change the microflora before analysis

5. References

Health Canada, Compendium of Analytical Methods, Volume 1 — Appendix B, November 2006: “Collection and Transportation of Samples: Applicable to All Methods in the Compendium of Analytical Methods.”