What you need to know, before it goes!
There are many things to consider when you are preparing samples to be sent out to your lab, you’re probably planning out when you’ll send your samples, considering lab test turnaround times, and when you can release and ship your product because time is money, right?! But even before all of that, first and foremost you must consider getting a representative sample to send out to the lab. This largely applies to product sampling but a representative sample is also applicable and important during environmental swabbing too. This blog will be centered on product sampling, representative portions and proper sample collection. Check back in for the next installment, regarding environmental swabbing and environmental swab submission to your lab.
The importance of representative sampling for food products cannot be understated. Obviously you cannot test 100% of your product, so the composites you choose to include in your sample can help you get a better idea of the quality and safety of your entire lot. If the sample you submit isn’t representative of your lot or samples are improperly collected/mishandled, then the laboratory results will not be accurate.
Why is a representative sample so important?
A representative portion of your sample is so crucial because often bacteria aren’t always evenly distributed throughout your entire product or throughout your lot. Within your finished product, pathogens or toxins are usually sparsely distributed. And when talking about your lot or production run, contamination could have occurred at the beginning, middle, end of your run, or anywhere in between. Taking a representative sample of your product, taking into account your product type as well as your production run can help ensure your results are accurate and consumers are safe.
What is a representative sample of my product?
The answer to that question can have a lot of variability based on your product. Product type matters because whether the food is solid, semisolid, viscous, or liquid can play a role in how you take your sample. Pathogens can be more easily homogenized throughout a liquid or a powder sample. However within a solid, semisolid or viscous sample, homogenization will be more difficult to achieve and focusing on obtaining representative portions
become even more vital.
When sampling a solid food product, for example a wheel of cheddar, composite units should be taken randomly from a wide variety of locations around the wheel. Remember pathogens don’t only reside in one area, they aren’t always going to be only on the surface, only in the middle, or only on the top/bottom, which is why it’s a good idea to get a representative portion and composite all units for testing.
When sampling a powder or a liquid, each sample should be mixed to ensure homogeneity before withdrawing a sample. Be sure to take samples throughout your production run to get a representative sample for the run/day’s production.
The number of units that can be deemed a representative portion of your product has to be statistically significant in proportion to the amount produced in your production run. More simply put- if you processed 40,000 gallons of milk, one 10ml sample from the beginning of your run would not be statistically relevant nor a representative sample for your lot. So although extra sampling and testing ends up costing extra money, it can save you in the long run from having to deal with a costly dreaded recall situation.
Making sure your samples are properly collected
There can be no compromise in the use of sterile sampling equipment and the use of aseptic technique when collecting your product samples. As stated earlier, if samples are not properly collected or mishandled, your lab results will not be accurate. If possible, sterilize your sampling equipment in an autoclave or dry-heat oven and keep the sampling tools in a sterile bag/container up until you are ready to sample. Be sure to use aseptic technique when opening your sample bag/container and depositing your sample. Do not let any unsterile item (your hand, unsterile part of the tool, equipment or other items) cross the plane into the bag when depositing the sample.
What else is good to know when submitting a sample to a lab?
If your product is prepackaged in a small enough container, please send the unopened packages to the lab. In most cases, it is best to not composite those types of products on your own prior to submitting them. We would like them to maintain their original packaged state and not have any chance for pathogens or contaminates to be introduced during additional nonessential handling steps. If products are in bulk or in containers too large to be shipped or brought to the lab, transfer representative portions to sterile containers under aseptic conditions.
Use containers that are the correct size for your product and are clean, dry, leak-proof, and most importantly, sterile. Whenever possible, avoid glass containers, which may break during shipment and lead to potential contamination. For dry materials, use sterile bags or packets with suitable closures. Sterile plastic bags (for dry, unfrozen materials only) or plastic bottles are useful containers for line samples. Take care not to overfill bags or puncture the bags with the wire closure.
Clearly identify your product description on the exterior of the container/bag, make sure that description matches what is listed on your Analysis Request Form (ARF) and deliver samples to the lab with the original storage conditions maintained as much as possible. Dry or canned foods that are not perishable and are collected at ambient temperatures, don’t need to be shipped with ice packs. Transport frozen or refrigerated products in approved insulated containers with ice packs so that they will arrive at the laboratory unchanged.