Buy IQF when fillets go straight to retail or kitchens and need to be used one piece at a time. Buy block-frozen (or interleaved "shatter" packs) when the product will be thawed in bulk or reprocessed: blocks pack more densely, cost less to produce and protect the fish well in long cold storage.
How each is made
IQF (individually quick frozen) – each fillet or portion is frozen separately, usually in a tunnel or spiral freezer, then given a thin protective ice glaze and packed loose in bags inside master cartons. You can take out exactly the pieces you need and leave the rest frozen.
Block frozen – fillets are packed together in a tray and frozen in a plate freezer into a solid block, often with a little water to fill the gaps. The whole block must be thawed to use it.
Interleaved or shatter pack – a middle option: fillets are layered with plastic sheets inside the block, so a sharp knock "shatters" the block into separate layers without thawing it all.
Comparison
| IQF | Block frozen | |
|---|---|---|
| Portion control | Excellent: use one piece at a time | Whole block thawed at once (shatter packs help) |
| Best for | Retail packs, restaurants, portion-controlled menus | Reprocessing, bulk kitchens, further processing plants |
| Protection in storage | Glaze protects each piece; re-glazing may be needed on long storage | Very good: the block itself limits air contact and freezer burn |
| Packing and freight | Less dense (air between pieces) | More dense: more product per carton and container |
| Production cost | Higher | Lower |
Glaze and net weight
Glaze is the thin layer of ice that protects IQF fish from drying out. It is water, not fish, so:
- Ask for the glaze percentage in writing (for example 10%).
- Buy on net weight excluding glaze. In major markets, the weight declared on the label must exclude glaze.
- Check it on arrival: thaw-and-weigh a sample to confirm the net fish weight matches the specification.
What to put in your specification
- Species and product form (e.g. Lates calcarifer, skinless fillet, deep-trimmed)
- Freezing method: IQF, block or interleaved
- Size grades and pieces per kg
- Glaze % and net weight per inner bag and per carton
- Packing: inner bag or tray, carton size and weight, labels
- Storage temperature: −18 °C or colder throughout the cold chain
Our barramundi is available both IQF and block frozen. See our barramundi specifications, read how barramundi compares with basa and tilapia, or request a quote.