Bluefin tuna
(Thunnus thynnus – Atlantic bluefin tuna; loins, fillets, belly cuts; fresh, frozen, smoked or canned)

Description

• Bluefin tuna (Thunnus thynnus) is a large, high-value pelagic species, prized for its strong, rich flavour and, in some cuts (belly/“toro”), high intramuscular fat with pronounced marbling, often compared to high-grade beef.

• Widely used raw (sushi, sashimi, tartare, tataki) in premium gastronomy, as well as grilled, seared or braised, and in high-end canned products in oil (fillets and belly).

• Flesh colour ranges from deep red in lean dorsal muscle to paler pink–red in heavily marbled areas; after cooking or canning, it becomes beige–pink and opaque.

Indicative nutritional values (per 100 g raw, lean dorsal muscle)

(Average values; very variable with cut, season, fat content and whether wild or ranched.)

• Energy: 140–190 kcal

• Water: ≈ 70–75 g

• Protein: 23–30 g

• Total fat: 4–7 g

  • First occurrence: SFA/MUFA/PUFA = saturated/monounsaturated/polyunsaturated fatty acids. In lean dorsal bluefin, total fat is moderate, with around 1–2 g/100 g saturated fat and a substantial share of MUFA and PUFA (including marine omega-3). Within a diet that keeps overall saturated fat moderate, this profile is generally more favourable than many red meats.

• Carbohydrates: 0 g

• Cholesterol: 35–45 mg

• Sodium (intrinsic): 35–50 mg

• Selected micronutrients (per 100 g, typical ranges):

  • Selenium: ≈ 50–80 µg (sometimes higher)

  • Niacin (vitamin B3): 8–15 mg

  • Vitamin B6: ≈ 0.8–1.0 mg

  • Vitamin B12: ≈ 2–9 µg

  • Phosphorus: ≈ 200–250 mg

  • Potassium: ≈ 300–450 mg

  • Heme iron: ≈ 1–2 mg

• Long-chain omega-3 (EPA + DHA): typically 0.4–1.5 g/100 g, with a wide range depending on cut and fatness.

Very fatty cuts and products in oil (belly, canned fillets)

• Fatty belly cuts (“toro”, “ventresca”) or canned fillets in oil may reach or exceed:

  • Energy: 300–350 kcal/100 g drained

  • Total fat: 20–30 g/100 g

  • Protein: ≈ 20–25 g/100 g

  • Salt: commonly ≈ 1 g/100 g in oil- or brine-packed preserves.

Key constituents

• Proteins

  • High biological value (BV) proteins with a full essential amino acid profile.

  • Rich in BCAA (branched-chain amino acids: leucine, isoleucine, valine), important for muscle metabolism and repair.

• Lipids

  • Moderately fatty in dorsal cuts; very fatty in belly cuts and in oil-packed products.

  • Contains saturated, monounsaturated and polyunsaturated fatty acids, with notable levels of marine omega-3 EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid).

  • No industrial trans fats; only minor natural marine trans isomers.

• Minerals and vitamins

  • Good source of selenium, phosphorus, potassium, vitamin D, vitamin B12, niacin, and heme iron.

• Other components

  • High histidine content, which can be converted to histamine if time–temperature control fails (scombroid risk).

  • Non-protein nitrogenous compounds and nucleotides that contribute to strong umami taste, plus myoglobin that drives the dark red colour.

Production process

(Overview for wild catch, ranching, fresh/frozen market and canned products.)

• Capture and landing

  • Caught using longlines, purse seines, fixed traps (tuna traps) and other gears under tight international management (e.g. ICCAT in the Atlantic/Mediterranean).

  • Rapid onboard chilling (ice, slurry, refrigerated seawater) is critical to limit spoilage and histamine formation and to preserve colour and texture.

• Ranching/fattening in cages

  • In the Mediterranean, bluefin is often captured alive (juveniles/adults) and transferred to offshore cages, where fish are fattened on forage fish until they reach desired size and fat content for sashimi markets.

• Primary processing

  • In plants or on board: evisceration, heading, washing.

  • Sectioning into large carcases, then loins, fillets, belly, tail, etc.

  • For high-end sashimi markets, very precise cutting and handling (including methods such as ikejime and spinal cord destruction) are used to optimise pH, colour and texture.

• Fresh/chilled and frozen products

  • Fresh: vacuum-packed or MAP-packaged loins and portions, distributed under strict cold chain.

  • Frozen: rapid freezing (blast, plate or ultra-low “tuna freezing” at e.g. −35 to −60 °C) to preserve colour and texture; glazing and packing; export and distribution.

• Canned and oil-packed products

  • Cooking or pre-cooking (steam or water) of selected cuts.

  • Removal of skin, bones and dark muscle as required.

  • Cutting into fillets, chunks or belly pieces, packing into cans/jars.

  • Addition of covering medium (olive or extra virgin olive oil, brine, other oils) and salt;

  • Seaming/closing and retorting (sterilisation);

  • Cooling, labelling and ambient storage.

Physical properties

• Highly pigmented muscle: deep red to bright crimson in lean parts; more marbled and paler red in fatty belly areas.

• Firm, dense structure with relatively thick muscle fibres; fatty areas feel softer and more unctuous.

• Typical post-mortem pH around 5.6–6.2; high water activity.

• In oil-packed products, added fat substantially increases energy and perceived oiliness and, when oils are good quality, can moderate oxidation.

Sensory and technological properties

• Flavour

  • Very intense, rich, “meaty” tuna flavour with pronounced umami; belly cuts are extremely succulent and complex, highly prized in gourmet cuisine.

• Texture

  • Dorsal loins: firm and dense, suited to raw/rare preparations and short cooking.

  • Belly: soft, buttery, almost melt-in-mouth when raw or lightly cooked; can become fragile with prolonged heat.

• Technological behaviour

  • Handles high-heat, short-time cooking (grill, pan) well when not overcooked; overcooking drives moisture loss and a dry, fibrous texture.

  • Excellent for tataki or seared outer surface with a rare centre.

  • In preserves, maintains defined fillets/chunks and a rich, oily mouthfeel.

Food applications

• Home cooking and foodservice

  • Raw or lightly processed: sushi, sashimi, tartare, carpaccio, tataki (where legally allowed and microbiologically safe).

  • Cooked: grilled, seared, baked steaks, stews and braises with tomato, legumes or vegetables; belly roasted or grilled, sometimes gently smoked.

• Artisanal and industrial

  • Fillets and belly in olive oil, often associated with Mediterranean specialties (Italy, Spain, etc.).

  • Smoked products, bluefin bottarga, specialty pâtés and spreads.

  • Fish meal and fish oil from heads, bones and trimmings for feed and ingredient uses.

Nutrition & health

• Bluefin tuna provides:

  • High-quality protein with high BV, contributing to maintenance and development of muscle mass.

  • Significant amounts of marine omega-3 EPA and DHA, which, in the context of a varied diet, contribute to:

    • normal heart function and more favourable blood-lipid profile;

    • support of certain brain and vision functions.

  • Substantial selenium, which participates in antioxidant systems and interacts with mercury, though the degree of protection in humans is still being studied.

• Lean dorsal cuts provide moderate fat; fatty belly and oil-packed products deliver much higher energy and total fat per portion and should be factored into daily energy and fat balance.

Mercury – high-concentration species

• Bluefin is a large, long-lived, apex predator and tends to accumulate high levels of methylmercury, often above 0.5 mg/kg and sometimes at or above 1.0 mg/kg in individual fish.

• As a result, it is usually classified among species to limit strongly or avoid for:

  • pregnant or breastfeeding individuals,

  • young children,

  • people with very high intakes of large predatory fish.

• Many national/international guidelines place bluefin and other large tunas in the category of fish that should be eaten only occasionally, favouring low-mercury species (small pelagics, cod, salmon, herring, sardines) for frequent consumption.

Histamine (scombroid) risk

• Like other tunas, bluefin is prone to histamine formation if time–temperature control is inadequate.

• High histamine can cause scombroid poisoning (flushing, headache, itching, gastrointestinal symptoms) typically within hours after the meal.

• Strict cold chain from catch to consumer, rapid chilling and proper handling are essential to minimise this risk.

Portion note

• As a main protein dish, a typical adult portion is 120–150 g cooked or drained.

• In raw preparations (sashimi, tartare), 80–100 g per portion is common.

• For vulnerable groups, any bluefin consumption should be occasional and limited, always balanced with low-mercury fish choices and in line with national advisories.

Allergens and intolerances

• Bluefin tuna is a fish allergen and must be labelled as such; it can trigger reactions in individuals with fish allergy.

• Prepared dishes (salads, pâtés, ready meals) may contain additional allergens such as soy, milk, egg, gluten, mustard, etc., which must be clearly indicated on labels.

• Histamine-related reactions are toxic pseudo-allergic events, not IgE-mediated, but can resemble allergic reactions clinically; they must be distinguished from true fish allergy.

Quality and specifications (typical themes)

• Composition

  • Protein, total fat (including detailed fatty acid profile), moisture and salt within specification.

  • For oil-packed products: defined fish-to-oil ratio and tight control of lipid oxidation.

• Physical/sensory

  • Uniform red colour (for fresh cuts) without excessive browning or dark oxidation patches.

  • Clean marine odour, free from rancid, ammoniacal or “stale” notes.

  • Minimal bones and unwanted tissues;

  • Appropriate texture (not mushy, not excessively dry).

• Chemical

  • Histamine below legal limits for scombroid fish.

  • Mercury and other heavy metals below regulatory maximum levels.

  • Peroxide value, anisidine value and other oxidation indicators controlled, especially in fatty and oil-packed products.

• Microbiological

  • Fresh/chilled: low total counts and absence of pathogens when held at 0–2 °C.

  • Sterilised preserves: commercial sterility throughout shelf-life.

Storage and shelf-life

• Fresh/chilled

  • Store at 0–2 °C (ice, refrigerated, often under vacuum or MAP).

  • Shelf-life is typically only a few days, strongly dependent on initial freshness, capture and bleeding method, handling and packaging.

• Frozen

  • Store at ≤ −18 °C; for sashimi-grade products, even lower temperatures (e.g. −35 to −60 °C) are often used to better preserve colour and texture.

  • Typical quality shelf-life: 6–12 months, with gradual sensory decline.

• Canned and oil-packed

  • Store unopened at ambient temperature in a cool, dry, dark place.

  • Typical shelf-life: 2–5 years depending on process and packaging.

  • Once opened: keep refrigerated (≈ 4 °C) and consume within about 3 days.

Safety and regulatory

• Bluefin tuna is subject to:

  • legal limits on histamine for scombroid fish;

  • maximum levels for mercury (often around 1.0 mg/kg for large predatory fish in many jurisdictions);

  • microbiological and hygiene criteria for fresh, frozen and canned products;

  • species, catch area and production method labelling requirements (“wild-caught”, “ranched/farmed”).

• Management of Atlantic and Mediterranean bluefin stocks is coordinated by ICCAT.

  • After severe overfishing and near-collapse in the past, stringent recovery plans and quotas have led to clear stock improvements, with many recent assessments considering the main Atlantic stock in good status, although sub-population uncertainties remain.

• Processing facilities must operate under GMP/HACCP, with CCPs for:

  • time–temperature control,

  • thermal process validation for canned products,

  • cleaning, sanitation and prevention of cross-contamination.

Labelling

• Common designations:

  • “bluefin tuna”, “Atlantic bluefin tuna”, “tonno rosso” (in Italian markets).

  • Best practice includes the scientific name Thunnus thynnus and FAO catch area.

• For processed products, labels should include:

  • full ingredient list with clear emphasis of the allergen fish and any other allergens;

  • type of covering medium (olive/extra virgin olive oil, brine, water);

  • net and drained weight;

  • nutrition declaration;

  • origin and, for premium products, possibly local/geographical indications and traditional techniques.

Troubleshooting

• Dry, fibrous steaks

  • Cause: overcooking of relatively lean cuts or excessively aggressive heat.

  • Actions: reduce time/temperature, use marinades, prefer quick searing and leave the centre pink/rare where safe.

• Excessive oiliness (belly and oil-packed products)

  • Cause: combination of high intrinsic fat and added oil.

  • Actions: moderate portion size; pair with acidic, bitter or high-vegetable side dishes; drain more thoroughly before use.

• Surface browning and oxidised smell

  • Cause: pigment and lipid oxidation due to oxygen, light and inadequate temperature.

  • Actions: improve packaging (vacuum/MAP), cold chain and time in display.

• Clusters of flushing/headache/itching after eating

  • Likely cause: histamine incident (scombroid).

  • Actions: test histamine on suspect batches, investigate time–temperature management, reinforce HACCP measures.

Sustainability and supply chain

• Bluefin tuna has a history of heavy overexploitation and high market value (especially for sashimi), with some stocks driven close to collapse in the past.

• In recent years, thanks to strict quotas, recovery plans and increased control, assessments indicate:

  • rising spawning biomass,

  • Atlantic stocks currently in much improved condition, with no overfishing detected in many recent evaluations, though uncertainties and regional differences persist.

• Ongoing concerns include:

  • impacts of ranching/fattening (removing wild juveniles for cage fattening rather than full aquaculture),

  • high carbon footprint associated with long-distance transport and deep-cold storage,

  • potential risk of renewed overfishing if controls are relaxed.

• Good practice along the chain:

  • preferential sourcing from well-managed, traceable fisheries and, where available, certified operations;

  • full utilisation of the fish (minimising waste, using trimmings for fishmeal/oil);

  • proper effluent management with attention to BOD/COD and recyclable packaging;

  • stock rotation using FIFO to limit oxidation, quality loss and waste.

Conclusion

Bluefin tuna (Thunnus thynnus) is an outstandingly flavourful, high-protein marine ingredient with a rich content of omega-3 fatty acids, selenium and key vitamins, especially in premium fatty cuts. Nutritionally, it can contribute positively to cardiometabolic and protein intake within a varied diet, but its high mercury burden makes it a food that should be consumed sparingly and thoughtfully, particularly by pregnant/breastfeeding women and children. Environmentally, despite notable progress in stock management, bluefin remains a high-profile species requiring careful attention to origin, quotas, traceability and sustainability credentials. Responsible use—moderate frequency, appropriate portion sizes, preference for well-managed sources and full utilisation of the animal—allows appreciation of its gastronomic qualities while minimising health and ecological risks.

Mini-glossary

• SFA/MUFA/PUFA – Saturated/monounsaturated/polyunsaturated fatty acids; in lean bluefin cuts, total fat is moderate with a substantial unsaturated fraction, while fatty belly and oil-packed products are very energy-dense; overall health impact depends on the total dietary pattern.

• EPA/DHA/ALA – Eicosapentaenoic acid / docosahexaenoic acid / alpha-linolenic acid; EPA and DHA are long-chain marine omega-3s linked to heart, brain and vision benefits; ALA is a plant omega-3 that the body can convert only partially into EPA/DHA.

• BV (biological value) – Measure of how efficiently dietary protein can be used for body protein synthesis; bluefin tuna has high BV.

• BCAA – Branched-chain amino acids (leucine, isoleucine, valine), important for muscle metabolism and recovery, abundant in fish and meat proteins.

• GMP/HACCP – Good Manufacturing Practices / Hazard Analysis and Critical Control Points; fundamental systems to ensure hygienic, safe and traceable processing of fish products.

• BOD/COD – Biochemical/Chemical Oxygen Demand; indicators of the organic and oxidisable load of wastewater, used for sizing and monitoring treatment plants in seafood and other food industries.

• FIFO – First In, First Out; stock-rotation principle whereby older lots are used before newer ones, reducing oxidation, expiry issues and waste.

References__________________________________________________________________________

Collette BB, Nauen C. FAO species catalogue, Vol. 2. Scombrids of the world: an annotated and illustrated catalogue of tunas, mackerels, bonitos, and related species known to date. FAO Fish Synop. 1983;125:1–137

Kojadinovic J, Potier M, Le Corre M, Cosson RP, Bustamante P. Mercury content in commercial pelagic fish and its risk assessment in the Western Indian Ocean. Sci Total Environ. 2006 Aug 1;366(2-3):688-700. doi: 10.1016/j.scitotenv.2006.02.006.

Abstract. As top predators of pelagic food webs, large fish naturally bioaccumulate mercury (Hg). Determining Hg burdens in commercialized fish is essential considering the concern about effects of contaminants on human health and the legal thresholds that are therefore set for local consumption and/or exportation. Total Hg levels were measured in the muscular tissue of 183 fish of five commercially important species from the tropical zone of the Western Indian Ocean. All individuals were measured and sexed in order to study the impregnation of Hg with size and sex within each species. Values of Hg found in this part of the Indian Ocean were comparable to Hg in muscular tissue of the same species studied in other areas. The highest Hg levels were noted in Swordfish (Xiphias gladius) caught in waters surrounding Reunion Island (3.97+/-2.67 microg g(-1) dry weight). Following the Swordfish, in decreasing order of Hg content, were the Yellowfin Tuna (Thunnus albacares) and the Skipjack (Katsuwonus pelamis), then the Common Dolphinfish (Coryphaena hippurus) and the Wahoo (Acanthocybium solandri). In the North of the Mozambique Channel, Swordfish had higher Hg levels than Yellowfin Tunas, and Dolphinfish exhibited intermediate Hg levels. The size of a fish was a determining factor of its Hg burden, as was the species. Differences in size-normalized Hg levels were observed between the two study zones for Swordfish and Common Dolphinfish. Sex, in contrast, did not influence Hg levels suggesting that females and males have similar feeding habits. The muscular Hg levels presented here suggest that consumers of fish originating from the Western Indian Ocean should limit themselves to one Swordfish based meal per week, or one fish meal a day if they choose to eat tuna or Common Dolphinfish.

Juan-Jordá MJ, Mosqueira I, Cooper AB, Freire J, Dulvy NK. Global population trajectories of tunas and their relatives. Proc Natl Acad Sci U S A. 2011 Dec 20;108(51):20650-5. doi: 10.1073/pnas.1107743108.

Abstract. Tunas and their relatives dominate the world's largest ecosystems and sustain some of the most valuable fisheries. The impacts of fishing on these species have been debated intensively over the past decade, giving rise to divergent views on the scale and extent of the impacts of fisheries on pelagic ecosystems. We use all available age-structured stock assessments to evaluate the adult biomass trajectories and exploitation status of 26 populations of tunas and their relatives (17 tunas, 5 mackerels, and 4 Spanish mackerels) from 1954 to 2006. Overall, populations have declined, on average, by 60% over the past half century, but the decline in the total adult biomass is lower (52%), driven by a few abundant populations. The trajectories of individual populations depend on the interaction between life histories, ecology, and fishing pressure. The steepest declines are exhibited by two distinct groups: the largest, longest lived, highest value temperate tunas and the smaller, short-lived mackerels, both with most of their populations being overexploited. The remaining populations, mostly tropical tunas, have been fished down to approximately maximum sustainable yield levels, preventing further expansion of catches in these fisheries. Fishing mortality has increased steadily to the point where around 12.5% of the tunas and their relatives are caught each year globally. Overcapacity of these fisheries is jeopardizing their long-term sustainability. To guarantee higher catches, stabilize profits, and reduce collateral impacts on marine ecosystems requires the rebuilding of overexploited populations and stricter management measures to reduce overcapacity and regulate threatening trade.