Keep counter-samples at least until the claim period in your contract has ended and the goods have been used or sold. Many buyers keep them until the end of the product's shelf life, because problems can appear later in a customer's product.
A counter-sample is a sealed portion of the same sample sent for testing, kept unopened as a reference if results are disputed.
Who keeps a sample
Sampling at loading usually produces at least three sealed portions from one mixed sample. A common arrangement is shown below. Seals and codes make each portion identifiable, as explained in what a sealed, coded sample is.
- One for testing before shipment.
- One kept by the supplier.
- One kept by you or your agent.
- Sometimes a fourth for an umpire lab, named in the contract.
Setting the period
Write the retention period into the contract so the supplier keeps their portion for the same time.
- Claim period: if the contract allows claims within a set number of days of arrival, keep samples well past that date.
- Use period: keep samples until the lot is fully used in production or sold.
- Shelf life: for ingredients that go into finished products, keep until the end of the finished product's shelf life.
- Legal or customer rules: some customers set their own retention periods. Follow the longest.
How to store them
A counter-sample is only useful if it has not changed. Moisture, heat and light can alter moisture content, colour, volatile oil and microbial counts. Insects can develop in poorly stored whole spices and seeds.
- Use clean, airtight containers or bags with tamper-evident seals.
- Label with product, lot number, date, seal number and who drew it.
- Store cool, dry and dark, away from strong odours.
- Keep a log of where each sample is and who has access.
- Do not open a sealed counter-sample except in front of both parties or at the umpire lab.
Size and quality of the sample
Each portion must be large enough for the full test set, including a retest. Aflatoxin and residue tests often need more material than buyers expect. Ask your lab how much they need per test and add a margin. Testing differences are covered in pre-shipment versus destination testing.
Counter-samples cannot help if they were drawn badly. A sample taken from the top of a few bags does not represent a lot of several hundred bags. Agree a sampling plan that takes material from many bags across the lot, mixes it and divides it. If the sample was not representative, a later dispute turns into an argument about sampling rather than about quality. That argument is hard for either side to win.
Where we come in
We draw and seal counter-samples at loading, log their codes against the lot and keep our portion under controlled storage for the agreed period. That gives you a clean reference if a claim arises. Start with a free sourcing review.