Cold-chain pallet wrap: condensation, fusing and rejection

Condensation, fusing and rejection land on three different budgets — plant time, warehouse labour, a commercial credit note — so they usually get treated as three separate problems and given to three separate people. They are one problem: water that was sealed into the pallet and had nowhere to go when the temperature moved.

A solid film does two things at once. It blocks water vapour, and it blocks air movement. Whatever was around the load at the moment of wrapping stays there — the humidity of the hall, the product’s own moisture, wash water on produce, ice glaze on frozen goods. In a cold chain the wrap is not a neutral bystander. It is the thing holding the water in.

End of line, chiller or blast cell, cold store, loading bay, trailer, ferry deck or cross-dock, depot, and finally the customer’s goods-in — sometimes with a warm yard in between. Every handover is a temperature step, and every step is another chance for the water in that trapped air to change state.

It fails in both directions. A warm load sealed and moved into the cold: the inner face of the film becomes the coldest surface in the package, water forms there and runs back down onto the cartons. A cold load brought out into warm, humid air: water forms on the outside of the wrap and reaches the goods the moment the film is cut. In a freezer, that water does not just sit there. It freezes.

Trapped vapour condenses on the coldest surfaces it can reach, which includes the outer faces of the cartons themselves. It collects in the narrow gaps where cartons touch and freezes there, bridging one to the next. The pallet that went in as a stack comes out as a block.

The cost is all downstream. Someone has to break it apart before the load can be picked, board tears, labels come away, and a mixed pallet cannot be split across orders. Because a solid film also slows the freeze, the load spends longer in exactly the band where all of this is happening — so the same wrap causes the fusing and extends the window in which it can happen.

Goods-in does not debate physics. It looks at the pallet. Wet or stained cartons, labels that have lifted or will not scan, rust speckle on lids and closures, ice inside the wrap, a stack that has started to lean — any one of those is grounds to refuse or discount the load, even where the product itself is untouched. Rust on a food can is not a cosmetic complaint.

Board is the quiet one. Corrugated takes up moisture and loses stiffness, so the columns that were carrying the stack stop carrying it and the load settles and leans on the road. And the real cost is never the film. It is the return leg, the credit note, the re-work, and a mark on a supplier scorecard that is harder to remove than any of them.

Aerosonic is a breathable stretch film with engineered perforations, so air moves through the load instead of stopping at the skin. Warm, moist air leaves with the airflow rather than collecting inside a sealed package, and cold air reaches the middle of the pallet instead of working inwards from the edges, so blast-chilling and freezing run faster. No trapped vapour means nothing to condense, and nothing to refreeze between the cartons.

The specification is the perforation. Hole size and hole count are engineered to the load rather than taken from a standard pattern, because that is what sets how much air actually moves. It matters more than it sounds: our team’s field experience is that rival perforated films can look identical on the roll and still underperform, because their holes do not open as the film is applied — the film itself will not stretch.

Not in Toreto’s range. Supersonic and Aerosonic are made from the same materials and perform the same way, so a plant can switch between the solid film and the breathable one at the same cost per pallet, on unchanged machine settings. Other breathable films on the market typically cost up to 100% more in use, and need settings of their own to perform adequately.

The measured comparison: in Toreto’s own wrap tests, on the same pallet and machine at the same power stretch and tension settings, Aerosonic and Supersonic at 16µ held 10 kg per square inch on 66 g of film per pallet, at roughly €0.32. The 23µ solid film held 9.9 kg per square inch on 200 g, at roughly €0.48. The reinforced films got there on about 50% fewer revolutions. Costs vary with film price and pallet size.

Give the supplier the route, not just the pallet. What the product is, what the carton is, how the stack is built, where and at what stage it is wrapped, and every temperature step between the wrapper and the customer’s door. Hole size and hole count are then set against that, in a machine or hand grade depending on how you wrap.

Then ask for the numbers to be measured on your own pallets rather than taken from a brochure: film weight per pallet, how well the load is held, and how the pallet behaves through your own chill or freeze. Those depend on your product and your stack, so they are confirmed per load at quotation. And if the wrap will touch unpacked product, ask for the food-contact position on that exact specification in writing.