Rethinking Salmon Shipping – Twin Tubs
Every year, Europe’s salmon industry ships over 2 million tonnes of fresh fish, and the vast majority travels packed in single-use expanded polystyrene (EPS) foam boxes with flake ice[1]. Flake ice can generally only chill fish to around 0 °C or just above the freezing point of water[2]. In an EPS box, the salmon’s core temperature rarely goes below 0 °C during transit. As a result, spoilage bacteria and enzymes remain active, slowly degrading quality and shelf life.
Today, an innovative transport method offers an alternative solution. It involves placing salmon in durable Twin Tubs (reusable insulated containers) and surrounding them with slurry ice, a pumpable “slush” of micro ice-crystals in brine which then holds the fish below 0 °C (around -0.5 to -1 °C) for the journey. This approach is proving it can deliver higher-quality fish while dramatically cutting costs.
Let’s explore why transporting salmon in slurry ice in Twin Tubs is a win-win for product quality and sustainability.
Faster, More Even Chilling with Slurry Ice
Slurry ice chills salmon much faster and more uniformly than flake ice. In a Twin Tub, liquid slurry ice can flow around every fish, eliminating air gaps and ensuring 100% contact with the surface[4]. The countless tiny ice crystals in the slush have a large total surface area, pulling heat out of the fish efficiently. Studies show slurry ice can chill seafood roughly three times faster than conventional flake ice or refrigerated seawater[4]. This rapid cooling means salmon reach the target temperature quickly after harvest, locking in freshness.
Equally important, slurry ice cools evenly and gently. Because it’s a fluid medium, it fills all voids between fish, avoiding warm spots that can occur with loosely packed ice cubes or flakes. The micro-crystals in slurry have a smooth, “gel-like” texture that cushions the fish[5]. Unlike hard flake ice shards, slurry ice won’t bruise or scratch the salmon’s skin. Fish essentially float in a cold suspension, so there’s no heavy ice pressing on them and no sharp edges, eliminating pressure marks and physical damage to the fillet. The slurry also envelops the fish and excludes air, which helps prevent dehydration of the flesh[6]. By the time the salmon are thoroughly chilled (usually within 10-15 minutes to about -0.5 °C core, depending on the cooling of the salmon prior to going into the tub), the tub’s drain ports are opened to remove excess ice-water. The fish are left lightly coated with ice crystals but no free water to slosh around. This means the salmon travel securely in the tub without shifting or getting jostled by loose ice[7]. In short, slurry ice provides rapid, uniform, and gentle chilling, a clear advantage over flake ice’s slower and uneven cooling.
Colder Temperatures Slow Spoilage (Without Freezing the Fish)
The slurry ice method also achieves something traditional flake ice cannot: keeping the fish below 0 °C for the entire trip. Ordinary flake ice made from fresh water can only maintain around 0 °C, but a slurry made with a bit of salt can remain liquid at subzero temperatures. In practice, salmon in slurry ice are maintained at approximately -0.5 to -1.0 °C in transit[8]. This is a game-changer for fish quality and safety. At these sub-zero (but non-freezing) temperatures, the growth of spoilage bacteria and the activity of degradative enzymes are dramatically reduced, far more so than at +0.x °C[9]. The fish flesh stays in what scientists call the “safety zone,” essentially near-freezing, where microbial spoilage is minimal. For consumers who enjoy salmon raw (such as in sushi or sashimi), this is especially crucial: fewer bacteria mean a safer, fresher product upon delivery.
Importantly, the salmon is not actually frozen solid at -0.5 to -1 °C as its delicate cell structure remains intact. Fresh fish muscle contains salts and other compounds that lower its freezing point below that of pure water. In fact, Atlantic salmon’s initial freezing point is around -1.5 °C[10]. This means the fish won’t begin to form ice crystals internally until roughly that temperature or below. Transporting salmon at about -0.5 to -1 °C thus keeps the fish ultra-cold without freezing it. Research on superchilling confirms that cooling fish to about 1–1,5 °C below the usual freezing point (i.e. around -1 °C for salmon) yields maximum freshness extension without freeze damage[11][12]. A small fraction of the water in the fish may turn to ice (often 5–20% of water content), but the fish tissue as a whole remains pliable, not solid frozen. This “partial freezing” greatly extends shelf life because microbes and enzymes are slowed down, yet the fish texture is preserved. As Iceland’s Matís food institute found, “superchilled salmon holds its water content better throughout processing, the fillets stay firmer, and shelf life can be extended by as much as a week” compared to conventionally chilled salmon[13][14]. In essence, by keeping salmon at a safe -1 °C instead of +1 °C, we gain several days of freshness without any freezing. The fish arrives in prime condition, even after long haul transport, thanks to this sub-zero chilling.
Preserving Quality: No Drip Loss, Firm Fillets, No Gaping
One of the most visible benefits of slurry-ice superchilling is how well it preserves the fish’s quality during transit. Processors report that salmon shipped in slurry ice arrive with noticeably less “drip loss,” the water and juices that otherwise leak out of fillets as they sit on ice. Because the fish’s core is so cold and much of its water is retained in the flesh (or even turned to micro ice within the muscle), very little fluid weeps out. In trials, seafood packed with slurry ice consistently showed minimal drip and firmer texture upon arrival[15]. A Norwegian study noted that Atlantic salmon stored 7 days in -1 °C slurry had higher water retention and remained in excellent sensory condition, whereas salmon stored in traditional ice had more drip and a shorter acceptable shelf life[16]. Simply put, superchilled salmon doesn’t get “soft and floppy” the way fish can when it sits at 0 °C for days. Instead it stays firm and rigor is delayed, which prevents the flesh from separating or gaping at the cut surfaces[13]. Fillets from superchilled salmon thus tend to have tight muscle texture and no gaping holes, even after further processing. This translates to a more attractive fillet for customers and higher fillet yields for processors, since less meat flakes off during cutting[13].
These quality improvements are not just theoretical, they’ve been proven in real-world tests. In Iceland, a trial at Arctic Fish’s processing facility compared sending salmon in slurry-ice Twin Tubs versus the standard EPS boxes. The result: no difference in fish quality or fillet yield between EPS and Twin Tub shipments[17]. In fact, in some batches the Twin Tub method produced slightly better yields because the fish were firmer and retained more moisture. Similarly, Dutch salmon importer Adri & Zoon partnered in pilot shipments using iTUB’s Twin Tubs and observed no drop in quality compared to their usual EPS box deliveries, in fact the salmon arrived in equally good (if not better) condition, with virtually no drip loss and no increase in gaping. According to iTUB, field tests with Adri & Zoon and Arctic Fish showed that fillet yields even improved in some cases when using Twin Tubs, thanks to the gentler cooling and lack of ice damage[18]. These findings echo the broader research: superchilled salmon “holds its water content better”, has firmer fillets with less gaping, and gives a higher culinary yield than conventionally iced fish[13]. For salmon farmers and processors, that means more sellable product at top quality. Even after a 4–6 day truck journey from, say, Iceland to central Europe, salmon shipped in slurry ice arrive bright, firm, and sashimi-grade fresh, with an extended shelf life on the market or in cold storage.
200 kg Twin Tubs – Keeping Fish Colder, Logistics Leaner
A key enabler of this method is the design of the Twin Tub containers themselves. Each Twin Tub is a rugged, tripple-walled insulated bin that can hold roughly 180-200 kg of head-on gutted salmon plus the slurry ice[19]. The tubs have built-in drainage valves on all four sides specifically for slurry ice use, allowing staff to easily drain out excess water after chilling. Draining the liquid out is important not only for temperature control but also for transport efficiency: it greatly reduces the total weight of each loaded tub. Traditionally, up to 20% of the gross weight of a salmon shipment could be just ice and melt-water[20]. With slurry ice and Twin Tubs, that extra weight is reduced – we ship more fish and far less ice. This directly saves on freight costs. It also makes handling easier and safer, since there’s no sloshing water inside the tub once drained. The salmon sit snugly in a chilled, moist environment without shifting in transit. The sturdy tub keeps them well-protected and stable.
A More Sustainable Cold Chain
Beyond quality improvements, the slurry ice + Twin Tub system offers major sustainability benefits. First is the drastic reduction in single-use packaging. Each reusable Twin Tub can be turned around hundreds of times over a lifespan of 12–15 years, replacing literally thousands of foam boxes. Estimates show one Twin Tub can eliminate about 1,800 EPS boxes over its life[23]. In an all-tub scenario, new plastic consumption for packaging drops by 97–98%, since you’re not manufacturing and trashing endless foam containers[23]. It aligns with the direction regulators and retailers are pushing – to get rid of unnecessary single-use plastics.
Secondly, the weight savings and improved efficiency translate to a lower carbon footprint. Hauling less ice and using containers more fully reduces fuel burn per kg of fish delivered. A lifecycle analysis by the University of Iceland, published in February of 2024, found that moving salmon in Twin Tubs can cut CO₂ emissions by around 80% compared to the traditional EPS box route (when evaluated over the full cycle including manufacturing, transport, and reuse)[24][21]. Also, because superchilling extends the salmon’s shelf life, it opens the door to more sustainable transport modes. With an extra 2-4 days of freshness to work with, exporters can opt to ship salmon by sea freight instead of airfreight in some cases[25]. Sea freight is far less carbon-intensive than flying fish to distant markets. The Nordic superchilling project noted that the longer shelf life “means fish can be transported by sea rather than by air” – saving a huge amount in transport costs and emissions[25]. In essence, superchilling gives the supply chain more flexibility to choose greener options without sacrificing quality on arrival.
Finally, the circular reuse model of Twin Tubs addresses a waste problem that has loomed over the salmon industry for decades. Currently, those 2+ million tonnes of salmon shipped each year come with an enormous pile of foam packaging waste as a byproduct[1]. By adopting reusable tubs even for a portion of shipments, the industry can dramatically reduce waste. Early adopters have shown that Twin Tubs can slot into existing operations without disrupting the cold chain[17]. For instance, Arctic Fish in Iceland and Scottish Sea Farm in Scotland have successfully integrated tubs alongside EPS, seeing equal fish quality and big drops in plastic waste[17][26]. It’s a proven concept: we can maintain the same (or better) fish freshness while cutting out tons of disposable packaging. This represents a huge opportunity for salmon farmers and processors across Europe to improve their sustainability profile.
Conclusion: Quality and Sustainability Go Hand-in-Hand
Transporting salmon in slurry ice with Twin Tubs at -0.5 °C to -1 °C offers a compelling way to transport salmon. The fish get chilled faster and colder, which locks in freshness and food safety; they suffer less physical damage and lose virtually no weight to drip, yielding firmer, higher-quality fillets for the market. At the same time, producers can save on ice weight, shipping costs, and plastic waste, making their operations leaner and greener. Slurry-iced salmon in tubs can arrive with up to 2-4 days more shelf life than ice-boxed fish[14], a tangible benefit for everyone from processors to retailers to end consumers. Perhaps most exciting is that these quality gains reinforce the sustainability gains: because the fish stays fresh longer, we can reduce wasteful practices (like excessive ice) and adopt more eco-friendly logistics without compromise. In short, the slurry ice Twin Tub method delivers salmon in peak condition while also shrinking the industry’s environmental footprint. With over 2 million tons of salmon still being shipped in throwaway EPS boxes annually[1], the potential impact of scaling up this solution is enormous. Forward-thinking salmon farmers and processors are already embracing it, reaping the rewards in product quality, shelf life, and cost savings, all while demonstrating environmental leadership. It’s clear that superchilled transport in Twin Tubs is not just a high-tech tweak to the cold chain; it’s a smarter, more sustainable way forward for the salmon industry. By keeping their fish ultra-fresh and their footprint low, companies can truly have the best of both worlds. The message is simple: when it comes to shipping salmon, colder and smarter is better; for business, for consumers, and for the planet.
Sources: Supporting data and research from iTUB, Nordic Innovation, and field trials by Adri & Zoon and Arctic Fish[17][18][13][4][8][9][10][20][21].
[1] [17] [21] [22] [23] [24] [26] Twin Tubs & EPS: A Sustainable Duo for Salmon Transport – iTub Rental
https://itub-rental.com/twin-tubs-eps-a-sustainable-duo-for-salmon-transport/
[2] Effects of newer slurry ice systems on the quality of aquatic food products: a comparative review versus flake-ice chilling methods – ScienceDirect
https://www.sciencedirect.com/science/article/abs/pii/S0924224404002225
[3] #avocado #export #sustainability #maersk #reefer #shipping …
[4] [5] [6] [7] [8] [9] [15] [16] [18] [19] Flake Ice vs. Slurry Ice – Two Advanced Methods for High-Quality Salmon Transport – iTub Rental
[10] Microsoft Word – Sub Chilling – Final Report
https://www.nordicinnovation.org/sites/default/files/inline-images/Subchilling%20Final%20Report.pdf
[11] [12] [13] [14] [20] [25] Superchilling of Fish | Nordic Innovation
https://www.nordicinnovation.org/programs/superchilling-fish
