IQF Fruit Cold Chain: -18 °C Storage, Thawing Risks and Shelf Life

Why is -18 °C the line?

-18 °C (0 °F) is the long-standing commercial storage temperature for frozen food, and in the EU it is a legal one. Directive 89/108/EEC requires quick-frozen foodstuffs to be kept at -18 °C or colder at all points in the product, with only brief upward fluctuations of no more than 3 °C allowed during transport. Regulation (EC) No 37/2005 adds that the air temperature in transport, warehousing and storage of quick-frozen food must be monitored and the records kept.

At -18 °C microorganisms do not grow. Quality, however, keeps changing slowly: ice crystals rearrange, surface moisture sublimes, and colour and aroma fade. The colder and steadier the storage, the slower these changes run. That is why the shelf life of frozen fruit is a quality limit, and why steady temperature matters as much as the set point itself.

What happens when IQF fruit thaws and refreezes?

Fast freezing, the “quick” in IQF, forms many small ice crystals inside the fruit tissue. When product warms up and freezes again slowly — in a warm terminal, during a long door opening, or in a reefer that lost power — water migrates and freezes into fewer, larger crystals. The consequences show on thawing:

• drip loss: juice runs out of damaged cells, so pieces weigh less and look deflated;
• softer, mushy texture: cell walls broken by large crystals no longer hold the fruit’s structure;
• clumping: moisture that reached the surface refreezes and welds pieces together;
• frost inside the pack: ice crystals on the bag walls are a visible sign that moisture moved;
• an unverifiable history: a refrozen lot can look frozen on arrival while its temperature record says otherwise, and any microbial growth that happened while it was warm is not visible.

Treat a suspected thaw as a quality investigation, not as a cosmetic defect.

Why do IQF pieces clump even without a major break?

Clumping has more causes than a failed container:

1. Surface water at freezing. Pieces that go into the freezer wet from washing or cutting freeze together.
2. Incomplete freezing before packing. If the core has not reached the target temperature, pieces keep exchanging moisture in the carton.
3. Temperature cycling. Repeated small rises in a cold store or at loading move moisture to the surface, where it refreezes as bridges between pieces.
4. Compression. Heavy stacking or weak cartons press soft pieces together.
5. Time. Long storage allows the effects of temperature cycling and moisture migration to accumulate.

If free-flowing product matters to your line, put it in the specification with a test: for example, the maximum share of fused clusters by weight in a defined sample, checked on arrival. “IQF” on the label alone does not guarantee it.

Why can frozen mango turn powdery or mushy?

Mango texture after freezing depends first on the fruit: variety, maturity at harvest and ripeness at processing. Over-ripe fruit gives soft, mushy dice; some varieties and maturity stages give a fibrous or mealy bite. Cutting damage, slow freezing, thaw and refreeze, and long storage then add to it.

Before assigning the cause of a texture complaint, compare the lot with the retained approval sample and with its temperature record. A texture problem that the retained sample shares may originate in the raw material, processing or specification; a difference between the lot and the sample warrants investigation of lot variation and handling after dispatch. Our IQF mango specification guide covers variety, maturity, Brix and cut tolerances.

What shelf life can you expect at -18 °C?

Our catalog states the frozen shelf life for our IQF fruits in the table further down, subject to validation for the product, pack and storage route. The figure assumes the product was stored at -18 °C or colder without interruption, in its intact original packaging. Colder storage slows quality loss further; repeated temperature swings shorten usable life even when the average temperature looks correct.

For retail packs sold in the EU, quick-frozen food also carries a batch mark, storage instructions and a clear statement such as “do not refreeze after thawing”. Agree who prepares that label text if you plan consumer packs.

How does the cold chain run from Vietnam to Europe or the USA?

A frozen shipment passes through several hands, and each hand-off is a place where temperature can slip:

A reefer container is built to hold a temperature, not to freeze warm cargo. The product has to be at its target temperature before it is loaded. For frozen fruit we arrange 20-foot or 40-foot reefer containers with the agreed set point and logging requirements, as described on our export logistics page.

What should you do if you suspect a break?

If a frozen shipment may have warmed up in transit, quarantine it and collect the evidence before deciding anything.

1. Quarantine the affected lot; do not release it or refreeze it “to be safe”.
2. Measure and photograph: product temperatures from several positions in the load, frost, clumping, deformed or drip-stained cartons.
3. Collect the records: the reefer controller download, independent logger data, and the loading and terminal records.
4. Call the surveyor and insurer early if the shipment is insured; under CFR and CIF the risk in transit is yours, as our Incoterms guide explains.
5. Compare with the retained sample and decide on use, downgrade or rejection with the supplier, on the evidence.

The contract should already say how excursions are investigated, which evidence counts, and the time limit for raising a claim.

Put the cold chain into the contract

Cold-chain duties are easiest to enforce when the contract states them. Include at least these points:

• storage and transport temperature (-18 °C or colder, or a colder figure if your process needs it) and the reefer set point;
• maximum product temperature at loading and how it is measured;
• number and position of independent data loggers, and who reads them;
• free-flow criteria and how clumping is assessed on arrival;
• carton strength, pallet pattern and maximum stack height;
• arrival checks, the claim window and the evidence required;
• retained samples from each lot and the temperature record in the shipment documents.

For packaging formats and container options, see IQF fruit packaging and shipping.