A chill chain breach investigation: pads as evidence

The load arrived at 04:20 with a probe reading of 9.1 °C and a data logger that said everything was fine. That contradiction is the normal starting point of a chill chain investigation, and it is where the pad in the bottom of the tray becomes more useful than people expect. Not as a thermometer. As a record of what happened to the pack while nobody was watching.

A pad holds a physical history: how much liquid it took, where the liquid went, whether it dried and re-wetted, whether the product sat on it under load. Read alongside a logger and a delivery note, those details narrow the window fast.

What a pad records that a logger does not

A logger in the airspace of a trailer tells you the air temperature. A logger inside one carton tells you that carton. Neither tells you whether the pallet was on the door end of the trailer for three hours, or whether the trays were stacked on their side for part of the run. The pad does, roughly, and roughly is often enough to choose between two explanations.

Four things are worth photographing before anything is moved: the pad in place under the product, the pad lifted and shot from below, the tray corner where liquid has collected, and the carton base. Take them at the loading dock, not after the product has been repacked in the chill room.

Reading the pattern: three shapes

Three patterns cover most of what we see:

• Even saturation across the sheet, wet to the edges and heavy: the pack was warm for a long period, and drip was continuous.
• One saturated corner with the rest dry: the tray travelled tilted or on its side, so all the liquid ran to one point.
• Dry sheet with a tide mark and a stiff, crusted edge: the pack warmed, drip was taken up, then the surface dried again. This is the signature of a warm spell followed by re-chilling.

The third is the interesting one, because it is the pattern that produces good logger data and bad product. Air temperature recovers quickly once a door is closed. A pallet of product does not, and the pad keeps the mark of the interval.

Writing it into the claim

A claim that says the product was warm will be argued. A claim that says the pad under case 14 was saturated to its edges with a tide line 30 mm from the sheet edge, while case 15 in the same pallet was dry, is much harder to dismiss, because it is a statement about a specific box that anyone can check.

We have seen an investigation go the wrong way for exactly this reason. A carrier was blamed for a three-hour delay, and the pad pattern showed the trays had been restacked upright at the depot, which put every drop at one corner and made a normal load look like a failure. The delay was real. The drip distribution was not evidence of it.

The second mistake is throwing the pad away before the photos are taken. Once the tray is emptied and rinsed, the only record left is a memory of a wet sheet, and a carrier will not accept that. Bag the pad, write the case number and the time on the bag, and keep it cold until the paperwork is signed. Photographs are cheaper than samples, but samples settle arguments.

One last detail: check the pad before the trailer is emptied, not after. A pad photographed in situ tells you where the product was sitting. The same pad photographed on a bench tells you almost nothing.

Keep the pads from a disputed load, bagged and labelled with the case number, until the claim is closed. They cost a few pence each and they are the only part of the consignment that still shows what happened. The absorbent pad user guide has a one-page photo checklist you can pin up at the receiving dock.