Introduction: A frozen seafood export pack normally uses two paper layers, and each layer solves a different problem.
Most frozen seafood buyers treat the inner liner and the master carton as two separate line items on a quote. In practice they behave as one system: the liner defines the block, the master carton carries the stack, and the pallet moves the whole thing. Following how protection passes from the fish surface up to the container floor makes it much easier to judge whether a packaging format fits a shipping plan, and where the weak point will show up when a load is handled badly.
In a frozen seafood export pack, the liner and the master carton do different jobs. The inner block liner is the part that touches the fish. A 7.5KG waxed block liner measures 481 × 253 × 60 mm, ships inside a poly bag, and is built as a food-contact inner box for frozen seafood, with a food-grade PE film as the standard barrier and wax coating available as an optional add-on. It forms the block, holds the portion weight, and keeps the frozen surface sealed. The master carton is the part that gets stacked, strapped, lifted, and shipped. The two layers work because a thin flexible barrier and a rigid outer shell cover each other's weaknesses. A liner on its own has almost no stacking strength; at 60 mm tall, nothing stops a column of them from leaning once the corners soften. A master carton on its own cannot protect the product surface, and frozen fish blocks need a tight, moisture-resistant layer right against the product to limit dehydration and surface damage during long cold storage. FAO guidance on freezing and refrigerated storage, and Torry advisory material on the composition of fish, both point to that surface-level protection as the part that decides whether a block still looks good after months in a freezer room. So the liner is a barrier and a mould, while the carton is a shell and a handle. Treating them as one unit produces a squarer pallet than optimising each one separately.
The 481 × 253 × 60 mm format is flat and shallow, and the 60 mm height is what allows a filled liner to sit inside an export master carton instead of behaving like a retail box. That single dimension controls four things at once, and each one changes how the outer carton behaves during transport.
These four points reinforce each other. A uniform liner gives the carton an even internal load, the carton transfers that load down its own walls, and the pallet then receives a stack that behaves like one block instead of a pile of loose boxes.
The pallet is the third layer, and in day-to-day operations it is the one that absorbs most of the abuse. Once cartons are stacked and strapped, forklifts, pallet jacks, and container loading act on the pallet as a single unit rather than on individual boxes. That changes where stresses land. The bottom cartons carry the compression of everything above them, straps stop the stack from spreading, and the pallet deck spreads the total weight across the container floor. A well-built liner and carton can still lose shape if the pallet is handled like loose freight. Cold-chain handling adds its own demands. A pallet that moves from a freezer room to a loading dock and then into a container meets different temperatures and humidity at every step, and paperboard takes on moisture at its exposed surfaces first. Keeping pallet corners aligned and cartons flush leaves fewer edges exposed to dripping condensation and to forklift tines, which are a common source of damage on lower layers. Good pallet practice is mostly about keeping the stack tight, square, and free of the gaps where ice, water, and steel can work their way in. Pallet patterns are not universal. How many cartons sit on one layer depends on carton size, block weight, and how the container is loaded, so the pattern is normally worked out per shipment. Cross-border shipments also meet different national packaging rules, and the WTO's technical barriers to trade work treats packaging requirements as an area exporters check market by market. Two paper layers plus one pallet plan is a practical packaging pattern, not a single fixed export configuration.
Frozen seafood export protection is easiest to understand as one chain: the liner seals and shapes the block, the master carton supplies compression strength and handling protection, and the pallet turns many cartons into one freight unit. A weakness in any of the three shows up as damaged corners, crushed bottom layers, or blocks that no longer look uniform on arrival. Buyers comparing formats get more value from reading liner height and carton dimensions together, then checking how the finished stack sits on a pallet, because that is where the design either holds or falls apart.
A：The liner does the close-contact work and the master carton does the load-bearing work. A 7.5KG waxed block liner wraps the frozen block tightly, keeps the surface sealed against moisture loss, and holds the portion shape, but at 60 mm tall it has almost no stacking strength. The master carton groups several liners, carries compression from the layers above, and gives forklifts and straps something solid to work with.
A：Height decides how many liners fit in each carton and how even the finished case turns out. When every liner shares the same 60 mm height, cases come out at a consistent height, pallet layers line up, and straps hold tension evenly across a square stack. Mix liner heights and the top of the case sits unevenly, so pallet layers tilt and the outer cartons take uneven compression.
A：The master carton adds compression strength, handling protection, and grouping. The liner is a shallow barrier with little vertical strength, so the carton walls carry the weight of the layers above and absorb contact from forklift tines, straps, and neighbouring pallets. It also provides a stable surface for printed identification and holds the individual blocks together as one unit for stacking.
Freezing and refrigerated storage in fisheries
TORRY ADVISORY NOTE No. 38 The composition of fish
WTO | Technical Barriers to Trade
