IQF vs Block: The Texture Playbook for Firm, Flaky Fish Every Time

If your thawed fish turns watery or mushy, it’s usually not your pan — it’s ice crystal physics and thaw discipline. Here’s a practical, science-backed guide from the Indonesia-Seafood Team to help you choose between IQF and block formats, thaw correctly, reduce drip loss, and lock in a firm, flaky bite.

We’ve run thousands of kilos of Indonesian fish through our plants and partner kitchens. The same pattern keeps showing up: texture is determined 70% by format and freezing speed, 20% by thaw discipline, and 10% by the species and cut. Get those first two right and you’ll stop asking why your fish weeps puddles after thaw.

The three pillars of firm texture

Format and freezing speed

IQF. Individually Quick Frozen pieces freeze fast so ice crystals stay tiny. That means less cell rupture and less drip loss during thaw. In our experience, well-made IQF fillets typically lose 2–4% weight in purge if thawed correctly.
Block. Slower freezing creates bigger crystals and more damage. Expect 5–10% purge, sometimes more if storage or transport wasn’t tight. Blocks can still be great for stews, curries, breaded items or value menus, but they need more gentle thawing.

Cold-chain discipline

Texture suffers after repeated temperature fluctuations, even with IQF. Keep fish between -18 to -25 C in storage and 0 to 3 C from the moment you start thawing. Don’t thaw on the counter. Ever.

Thaw method for the job

Firm, flaky saute or grill. Choose IQF portions or fillets. Thaw fast at low temperatures or cook from frozen with proper technique.
Soups, curries, breaded. Block can be cost-effective. Thaw long and cold, separate carefully, then finish in sauce or batter where slight softness won’t show.

Practical takeaway: If texture is your top KPI, choose IQF. Then protect it with strict temperature control and a planful thaw.

Fast, safe thawing that protects texture

Here’s the thing. Speed matters, but only inside a cold window. Slow room-temp thawing causes enzymatic breakdown and bacterial growth that reads as mush.

Fridge thaw (0–3 C). Best texture, lowest risk. Allow 8–12 hours per 2.5 cm (1 inch) of thickness for IQF. For block, plan 18–24 hours per inch to reach “sheet separation” stage, then finish as below.
Cold-water thaw (0–5 C). Fast and safe if you keep it cold. Submerge sealed fish in circulating or frequently changed cold water. Thin IQF fillets: 30–45 minutes. Thicker portions: 45–90 minutes. Change water every 30 minutes.
Hybrid for blocks. Thaw the block in the fridge until the outer fillets can be gently separated. Transfer separated pieces to a cold-water bath to finish. This avoids tearing and reduces soak time that can soften the surface.

Two extra steps most kitchens skip:

Open ROP before fridge thaw. Remove vacuum packaging before refrigerator thaw to prevent anaerobic conditions linked to C. botulinum growth. For cold-water thaw, open the original vacuum, then place fish into a non-airtight, food-safe bag to keep water out while allowing air space.
Air-dry chill. After thawing, set fish on a rack, uncovered in the fridge for 15–30 minutes. Pat once more just before cooking. That brief surface drying changes everything for searing.

Can cooking from frozen improve firmness?

Often yes, with IQF. Cooking from frozen skips the long thaw phase where drip loss happens. You’ll add about 50% to the cook time and need a little technique.

Pan sear from frozen. Rinse off any surface frost and dry aggressively. Sear skin-side down in a hot, lightly oiled pan for 2–3 minutes to set structure. Flip, lower heat, and finish gently. For thick portions, move to a 180 C oven to finish.
Batter and fry from frozen. Works beautifully with uniform IQF cuts. Fry at controlled oil temperature and don’t overcrowd.

We use this approach for IQF portions like Mahi Mahi Portion (IQF) and Swordfish Steak (IQF) in busy hotel kitchens that need repeatable outcomes.

Why is my thawed fish mushy or watery?

Three usual culprits:

Big ice crystals from slow freeze or old inventory. Cells rupture and leak. You can’t fully undo this, but you can reduce the damage with smarter thawing and drier cooking.
Warm or slow thaw. Enzymes and microbes soften muscle. Use fridge or cold-water methods and keep fish near 0–3 C.
Over-thawing in water. Long soaks dilute flavor and soften the surface. Aim for just-done thawing and then air-dry chill.

Fresh vs IQF for ceviche or crudo

For raw or near-raw dishes, texture and safety are non-negotiable. Fresh never-frozen fish with tight handling can feel slightly snappier. But high-grade IQF, frozen very fast, can be excellent and far more consistent across seasons and shipping lanes. Choose firm, low-moisture species and sashimi-grade handling. For example, our Pinjalo Fillet (IQF) and Cobia Fillet (IVP / IQF) are popular for sushi and crudo when buyers want predictable texture across volumes.

Context matters. If your supply chain can’t guarantee same-week “fresh,” a premium IQF fillet often beats a tired fresh fillet that took the scenic route.

The decision flow we use with chefs

Define the dish texture outcome

Crispy sear or grill, distinct flakes. Choose IQF fillets or portions. Try Grouper Fillet (IQF), Sweetlip Fillet (IQF), or Snapper Fillet (Red Snapper).
Raw, ceviche, poke. Sashimi-grade IQF or ULT-frozen tuna. Consider Yellowfin Saku (Sushi Grade) or sashimi-grade Bigeye Loin.
Batter fry, stew, curry. IQF or block both work. Block offers value if you follow the hybrid thaw. For block options, see Mahi Mahi Fillet. For IQF convenience at the line, we lean to Grouper Bites (Portion Cut).

Pick the thaw path

IQF for sear/grill. Cold-water thaw to “just pliable” plus 15–30 minutes air-dry chill. Or cook from frozen if service is tight.
Block for sauce dishes. Fridge thaw to sheet separation, then finish in cold water. Don’t soak longer than needed.

Lock in the sear

Pat dry. Season lightly. For added firmness, dry-brine 1% salt by weight for 15–30 minutes, then rinse and dry.
Hot oil meets dry surface. Sear to set the exterior, then finish gently to target temperature.

If you want help matching formats and thaw protocols to your menu and equipment, reach out and we’ll share a simple SOP we use with export clients. Questions about your project? Give us a call.

The fastest safe way to thaw without ruining texture

Cold-water thaw wins when you need speed and quality. Keep water near 0–5 C, change it every 30 minutes, and stop the moment the fish is flexible. Transfer to a rack for 15–30 minutes in the fridge to dry the surface. Cold-water thaw setup on a stainless counter: a clear bin filled with icy water submerging a loose clear bag of fish held by a gloved hand, with an open fridge in the background showing fillets air-drying on a wire rack.

Typical timelines:

150–200 g IQF portions. 30–45 minutes in cold water.
250–350 g steaks or thick fillets. 45–90 minutes in cold water.
1-inch fish in the fridge. 8–12 hours if IQF. 18–24 hours from block to separate, then finish in cold water.

Should I remove vacuum packaging before thawing fish?

Yes for fridge thaw. Open or remove the vacuum to avoid anaerobic conditions. For cold-water thaw, open the original vacuum package, then move fish into a non-airtight, food-safe bag to keep water out while allowing air space. Always keep products at 0–3 C during and after thaw.

Common mistakes that kill texture

Thawing on the counter. Fast on the outside, warm in the core. This is how you get mush and off aromas.
Thawing sealed in ROP in the fridge. See the safety note above.
Long water soaks. You’ll wash out flavor and soften the surface.
Over-marinating acidic mixes. Acid cooks proteins and can turn already-delicate fish into paste. For ceviche, balance acid time with the species’ firmness.
Not drying enough before heat. Water on the surface steams your sear.

Real-world pairings that perform

These are combinations we recommend to buyers who obsess over texture:

Crisp taco or sandwich fish. Mahi Mahi Portion (IQF), cooked from frozen or cold-water thawed, quick dry-brine, hard sear, finish in oven.
Upscale grill with defined flakes. Grouper Fillet (IQF) or Goldband Snapper Fillet. Fridge or cold-water thaw, air-dry chill, high-heat sear.
Sashimi or crudo programs. Yellowfin Saku (Sushi Grade) and sashimi-grade Pinjalo Fillet (IQF) where permitted by your HACCP.

What’s interesting is how much consistency improved in the last 6 months as more operators moved to standardized cold-water thaw and cook-from-frozen SOPs. Even small teams can now hit a high batting average on texture, service after service.

Quick answers to FAQs we hear daily

Is IQF fish less mushy than block frozen? Generally yes. Faster freezing equals smaller crystals and less damage. You still need good thaw discipline.
What’s the fastest safe way to thaw? Cold water at 0–5 C with frequent water changes. Stop the moment fish is flexible and finish with an air-dry chill.
Should I cook from frozen to keep it firm? Often a good choice for IQF portions and steaks. Plan 50% more cook time and focus on surface drying.
How long to thaw fish in the fridge per inch? IQF: 8–12 hours per inch. Block to separable sheets: 18–24 hours per inch, then finish in cold water.
Why is my fish watery after thawing? Ice-crystal damage, warm-thaw damage, or long water exposure. Fix with IQF format, cold-water thaw, and air-dry.
Is fresh less mushy than frozen for ceviche? If truly fresh and tightly handled, yes, it can feel snappier. But premium IQF sashimi-grade is an excellent, consistent alternative.
Should I remove vacuum packaging before thawing? Yes for fridge thaw. For cold-water thaw, open the vacuum and rebag without a tight seal.

If you want to test side-by-side formats for your menu, we’re happy to suggest SKUs and a simple drip-loss trial protocol. Need help with your specific situation? Contact us on whatsapp. Or browse what we offer and match formats to your dishes: View our products.