Did the ice cream melt on the way, and can you tell by opening the pack? Usually, yes. Ice cream that melted and refroze looks sound from outside, and the temperature record can be clean too, because the event may have happened before delivery, in the backroom or during a cabinet failure. The product carries the trace inside.
| Sign | Where it shows | What it means |
|---|---|---|
| Ice crystals under the lid | Inner face of the pack | The surface melted and refroze |
| Shrinking from the wall, collapse | Shape of the pack | Air cells merged, volume lost |
| Gritty, icy feel on the spoon | Inside the product | Ice crystals have grown |
Why there is no way back
The smooth texture of ice cream depends on small ice crystals. According to Park and colleagues (2015), consumers find crystals below about 55 micrometres smooth, while larger ones feel icy and sandy. When temperature fluctuates, small crystals melt and refreeze onto larger ones, and freezing the product again does not undo that growth. In the same study, ice cream held at -18 °C for 52 weeks saw crystal size rise from 40 to 100 micrometres, while at -50 °C it stayed at 57-58 micrometres.
The riskiest moments are outside the cabinet. A cabinet that works correctly causes no trouble. The risky moments are the transitions: moving from vehicle to cabinet, waiting in the backroom, the cabinet's defrost cycle and an interruption while the store is closed. The few minutes from vehicle to cabinet are the most exposed link. Over that distance a closed insulated container keeps the product out of the ambient air without lengthening the trip, and it doubles as a holding place when a cabinet fails.
At goods-in, a pack showing the signs is photographed, entered on the receiving note with its lot code, and a few more packs from the same lot are opened. If the same sign appears on more than one pack, the lot stays off sale until a decision is made and the supplier is informed together with the temperature record. A sign on a single pack is the starting point for finding where in the chain that pack warmed up.
