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06 · Blast freezing

Freezing is not
storage. It is a process.

Almost every quality problem in frozen fish is decided in the twenty minutes it spends between −1 °C and −5 °C. Here is what happens in that window, why the facility we are building goes far below the legal minimum — and where our −30 °C store stands in the meantime.

The critical zone

Between −1 °C and −5 °C,
the fish is decided.

This band is the maximum ice-crystal formation zone. Cross it slowly and water inside the muscle cells migrates out and forms large crystals between them, which puncture cell membranes. Thaw that fish and the cell contents run out as drip: weight loss, texture loss, flavour loss.

Cross it fast and you get many small crystals formed in place, cell walls largely intact, and a thawed fish that still behaves like fresh fish. The Codex standard for quick-frozen finfish puts it plainly: the freezing process must be carried out so that “the range of temperature of maximum crystallization is passed quickly”.

Codex STAN 36-1981, Rev. 1-1995, Quick Frozen Finfish. Product must reach −18 °C or colder at the thermal centre after stabilisation and be held there through transport and distribution.

MAXIMUM ICE-CRYSTAL FORMATION ZONE −1 °C to −5 °C +10 °C0 °C −5 °C−18 °C −45 °C 0 h2 h 6 h12 h24 h Slow freeze — hours in the zone Blast freeze — minutes in the zone

Schematic comparison of freezing curves, drawn to illustrate the mechanism. Not measurement data from our tunnel — per-lot curves are published in the lot record.

The numbers that matter

Four temperatures, and what
each one actually means.

−18°C
The legal floor. EU law requires frozen fishery products to be kept at not more than −18 °C in all parts of the product. Meeting this is compliance, not quality.
Reg. (EC) 853/2004, Annex III §VIII ch. VII(2)
−30°C
Where we are today. Our store freezes and holds at −30 °C, checked and written down. Well inside the law, and not yet what the science below asks for.
Samaki Bluu cold store, 2026
−35°C
The parasite parameter. FDA accepts −35 °C until solid then held 15 hours; or −20 °C for 7 days. EU accepts −35 °C for 15 hours or −20 °C for 24 hours.
FDA Fish & Fishery Products Guidance ch. 5; Reg. 853/2004 Annex III ch. III(D)(2)
−45°C
The facility specification. A −40 °C core at the end of the blast cycle, logged per lot by the tunnel controller, and a −45 °C hold — the point below which tuna colour stops moving.
Planned · Nakazawa, Okazaki et al. (2020), Int. J. Refrigeration 112: 270–280

Why the new facility is specified at −45 °C rather than −35 °C. The same study found that meat with a pH above 6.8 held its colour at −35 °C, but meat with a pH below 6.2 needed −45 °C or colder. You do not know the pH of every fish before you freeze it. Holding the whole store at −45 °C means the specification works for the worst fish in the batch, not the average one. Across the storage period, K-values — the standard freshness index — rose by less than 7.5% in all samples. Today we hold at −30 °C; this page explains what we are building towards, not what we ship now.

Drip loss

What slow handling
costs you in the pan.

Drip loss is the most honest quality measure there is, because you can weigh it. Published work on tuna fillets after ten days of storage measured it across the temperature range.

Drip loss in tuna fillets after 10 days’ storage, by storage temperature.
Storage temperatureCutDrip loss
−18 °COtoro1.84%
−18 °CChutoro1.87%
−18 °CAkami2.86%
0 °CChutoro15.18%
+5 °CChutoro19.77%

What this table does not show. It compares frozen against chilled. It does not compare −18 °C against −40 °C, and we are not going to imply that it does. We have found no published figure for drip loss at ultra-low temperature versus −18 °C, so we do not quote one. The case for −45 °C rests on the colour and oxidation research above, not on drip.

Sarah, Marwati, Misran & Madinah (2024), Applied Food Research 4(2), DOI 10.1016/j.afres.2024.100648.

Histamine

The one that
cannot be fixed later.

Scombroid species — tuna and kingfish among them — build histamine enzymatically once the fish warms. It is not destroyed by cooking, freezing or canning. There is no recovery step. The only control is speed on the boat.

Regulatory histamine limits for high-histidine species.
AuthorityThresholdMeaning
EU — Reg. 2073/2005m = 100 mg/kgSampling plan n = 9
EU — Reg. 2073/2005M = 200 mg/kgAbsolute maximum
US FDA — CPG 540.52535 ppmDecomposition indicated
US FDA — CPG 540.525200 ppmHealth hazard
Samaki Bluuawaiting first results from the labBatch testing begins with the laboratory programme; the release limit will be published here with the first results

Note the date on the FDA numbers. FDA revised this guidance in November 2024, tightening the decomposition threshold from 50 ppm to 35 ppm and the hazard threshold from 500 ppm to 200 ppm. A great deal of industry material still quotes the old figures. If a supplier is still citing 50/500, their documentation is at least two years out of date.

Commission Regulation (EC) 2073/2005; FDA Compliance Policy Guide Sec. 540.525, revised 4 November 2024.

On the words “sashimi grade” and “super-frozen”. Neither has a legal definition in the EU or the United States. The only regulated thresholds in this entire area are the parasite-destruction parameters and the −18 °C storage floor. When we use the terms, we state the temperature we actually achieved alongside them, because the temperature is the claim and the adjective is not. We would encourage you to hold every supplier to the same test.

Page last reviewed 21 September 2026. Sources: Reg. (EC) 853/2004; Reg. (EC) 2073/2005; Codex STAN 36-1981 Rev. 1-1995; FDA Fish and Fishery Products Hazards and Controls Guidance ch. 5; FDA CPG Sec. 540.525 (rev. 2024); Nakazawa, Okazaki et al. (2020) Int. J. Refrigeration 112: 270–280; Sarah et al. (2024) Applied Food Research 4(2).