A seafood can is a protection system, not just a metal container.
The can body, internal coating, lid, sealing compound, and double seam work together. They block light and external contamination, maintain a hermetic seal, and protect the product during retort processing, transport, and storage.
Canned seafood includes fish, shellfish, and crustacean products packed in sealed containers and thermally processed to achieve commercial sterility. The product may be whole, sliced, packed as fillets, or processed into chunks, flakes, or shredded meat. Common packing media include water, brine, oil, and sauce.
Metal cans are widely used because they provide a strong barrier against oxygen, moisture, light, and contamination. They also tolerate the heat and pressure used during thermal processing. This allows many seafood products to move through the supply chain without refrigeration.
Demand for these products continues to grow. FAO data indicates that global tuna trade volume increased by about 28% in 2024, partly due to stronger demand for canned tuna. The United States imported about 230,557 tonnes of canned and prepared tuna during the same year. (fuente)
More volume does not make package selection simpler. Fish species, product size, salt level, packing medium, retort schedule, and target shelf life all affect can performance.
The real question is straightforward: can the complete package protect the actual product under real processing and storage conditions?
1. Common Types of Seafood Cans
Different seafood products require different can shapes, filling methods, coatings, and opening systems.
| Producto | Common Product Forms | Typical Can Formats | Main Packaging Requirements |
|---|---|---|---|
| Tuna | Solid, chunk, flakes, grated, or shredded | Round two-piece cans, three-piece cans, bowl-shaped cans, and some oval cans | Filling consistency, drained weight, sulfide staining, and easy opening |
| Sardines | Whole, headed, gutted, boneless, or skinless | Small rectangular cans, oval cans, and shallow round cans | Product presentation, oil oxidation, sulfides, and non-round end sealing |
| Mackerel | Fillets, pieces, or whole fish | Rectangular, oval, and round cans | Sauce or oil compatibility, fillet integrity, and easy-open ends |
| Anchovies and herring | Fillets or small whole fish | Small rectangular and oval cans | High-salt formulations, shallow presentation, and coating validation |
| Salmon | Chunks, solid pack, skin-on, or bone-in | Round and shallow round cans | Large solid pieces, heat penetration, sulfides, and color protection |
| Eel | Pieces, fillets, or sauce-packed | Rectangular and oval cans | Sauce compatibility, sugar and salt levels, and product placement |
| Crab | Lump meat, flakes, or body meat | Round, shallow round, and some rectangular cans | Meat color, metal-contact discoloration, and suitable liners or coatings |
| Shrimp | Peeled or whole shrimp | Round and shallow round cans | Shrimp size, heat penetration, and color retention |
| Clams and oysters | Whole meat, pieces, or smoked products | Round and rectangular cans | Salt content, sulfides, smoke flavor, and oil compatibility |
| Abalone | Whole, sliced, or sauce-packed | Round and shallow round cans | Product appearance, coating performance, and opening experience |
Codex classifies canned tuna into forms such as solid, chunks, flakes, and grated or shredded tuna. Each format creates different filling and drained-weight requirements. (fuente)
Canned sardines may be packed in water, oil, or another suitable medium. Codex also requires a can to contain at least two fish from one species. (fuente)
Can shape often follows the product. Rectangular and oval cans are well suited to whole small fish and fillets because they provide a shallow display area. Round cans are practical for tuna, salmon, crab, shrimp, and other products packed as chunks or loose pieces.
2. Can Body Shapes and Construction
Seafood cans are generally produced as two-piece or three-piece containers.
A two-piece can has an integrated body and bottom. Only the top end is double seamed. Common processes include Draw and Redraw, known as DRD, and Draw and Wall Ironing, also called DWI or D&I. Two-piece construction is common for shallow round, rectangular, tapered, and bowl-shaped cans.
A three-piece can consists of a welded body, a bottom end, and a top end. It provides more flexibility in can height and diameter and works well with established round-can filling lines. The welded side seam requires a suitable repair coating because it remains part of the internal food-contact surface.
The lid may be a full-aperture easy-open end, a peelable end, or a standard sanitary end. End selection should not be based only on convenience. Opening force, score stability, post-retort panel movement, stacking clearance, edge condition, and seam specifications all need to be checked.
For non-round cans, corners and changes in panel geometry can affect both opening performance and seam control. Testing should therefore use the actual can shape, lid, seamer, and retort process.
3. Packaging Seafood in Oil, Water, Brine, and Sauce
The packing medium changes the chemical conditions inside the can. A coating that works with tuna in water may not perform the same way with sardines in tomato sauce.
Coating selection should be based on the complete formulation rather than the seafood species alone.
3.1 Oil-Packed Seafood
Common products include:
- Canned sardines in olive oil
- Canned sardines in extra virgin olive oil
- Canned mackerel in olive oil
- Tuna in vegetable oil
Oil-packed seafood needs protection from oxygen and light because both can accelerate oxidation and affect flavor.
The package must control residual oxygen, headspace, vacuum, and seam integrity. The internal coating also needs to tolerate oil contact during retorting and long-term storage.
Persistent oxidized or rancid odors are treated as product defects under Codex standards for canned tuna and sardines. For seafood packed in higher-value oils, can appearance and opening performance may also receive more attention.
3.2 Water-Packed Seafood
Common products include:
- Canned tuna in water
- Tuna packed in water
- Water-packed tuna
Water-packed products are often positioned around a lighter flavor and easier draining. From a packaging perspective, the main concerns are coating coverage, long-term contact with the water phase, vacuum, headspace, and drained weight.
Small coating defects may become more significant when an aqueous medium remains in direct contact with the metal.
Opening behavior also matters. High vacuum or excessive filling may cause liquid to splash when the lid is removed.
3.3 Brine-Packed Seafood
Common products include:
- Tuna in brine
- Sardines in brine
- Saltwater-packed fish
- Canned fish in brine
Salt concentration affects product corrosiveness, but it is only one part of the formulation.
The coating system should be qualified against the actual salt concentration, food composition, retort process, and target shelf life.
Sulfide exposure, acidity, mechanical forming, and processing temperature may all change coating performance. There is no single internal coating that can be assumed to work with every brine-packed seafood product.
3.4 Tomato Sauce and Other Acidic Sauces
Common products include:
- Canned sardines in tomato sauce
- Mackerel in tomato sauce
- Canned fish in spicy tomato sauce
- Sauce-packed seafood
Tomato sauce, vinegar, chili, salt, sugar, and spices can create a more aggressive food system than plain water or oil.
Testing should use the final sauce formulation rather than the base ingredient alone. The can body, ends, score area, and side-seam repair coating should all be included.
Sauce-packed products may also require a different drained-weight method. Codex provides a washed drained weight procedure for some sardine products packed in sauce. The measurement method used for water-packed seafood cannot always be applied without adjustment.
4. Internal Coatings and Sulfur Resistance
The internal coating forms a barrier between the seafood and the metal substrate. It helps reduce corrosion, staining, flavor changes, and product discoloration.
Seafood specifications often refer to sulfur-resistant coatings, sulfide stain resistance, retort-resistant lacquer, or coatings for chemically aggressive foods.
Fish and shellfish may release sulfur-containing compounds during thermal processing. These compounds can react with exposed metal and create dark marks on the can or product. Codex treats sulfide staining beyond defined limits as a defect in canned tuna and sardines.
A sulfur-resistant coating can reduce this reaction, but its performance depends on coating chemistry, thickness, coverage, curing, food formulation, forming conditions, and retort severity. A coating tested on a flat panel may behave differently after drawing, scoring, flanging, or seaming.
Crab meat presents another issue. Direct metal contact can cause discoloration during processing and storage. Some crab products therefore use full liners, end liners, or other barriers. This is a product-color problem, not simply a rust problem.
Canned fish may also develop struvite crystals. These are magnesium ammonium phosphate crystals formed within the product. Consumers sometimes mistake them for glass, but they do not come from the can material. Codex identifies crystals longer than 5 mm as a defect.
For European projects, coating descriptions may include non-bisphenol, BPA-NI, PFAS-NI, or EU food-contact-compliant. These terms should be supported by supplier declarations and test documentation.
BPA-NI normally means that bisphenol A is not intentionally used in the coating formulation. It should not be presented as an absolute zero-detection claim without supporting analytical data.
5. Retort Processing and Hermetic Sealing
Can size and thermal processing cannot be approved separately.
Canned seafood is usually a low-acid food packed in a hermetically sealed container. The product must follow an established and validated thermal process that achieves commercial sterility.
Heat penetration depends on can dimensions, product piece size, fill weight, product arrangement, packing medium, sauce viscosity, headspace, initial temperature, and retort method.
Large pieces may heat more slowly than small pieces. Product arrangement can also change the heating pattern. For example, large shrimp may require more processing time than small shrimp at the same retort temperature. They may also pack differently inside the can.
A shallow rectangular can and a tall round can should not be expected to behave the same way, even when the net weight is similar.
Claims such as “suitable for all seafood sterilization processes” should be avoided.
The can and end should be qualified using the customer’s actual product formulation, fill weight, retort schedule, and filling line.
The double seam is part of this qualification. Seam performance depends on the can flange, end curl, sealing compound, metal thickness, chuck, rolls, and seamer settings.
Visual inspection alone is not enough. Seam measurements should follow the approved specifications supplied for the can, end, and seaming equipment.
6. Questions to Confirm Before Approving a Seafood Can
Before approval, the packaging team should confirm the seafood species, product form, packing medium, salt and acid levels, can dimensions, coating system, lid type, retort schedule, seaming specification, and target shelf life.
The package should then be tested using the final formulation and production process. Testing an empty can, a flat coated panel, or a different packing medium does not provide enough evidence.
The final review should answer three practical questions: does the coating protect the product, does the seam remain hermetic, and does the package remain stable after retorting and storage?
7. Final Engineering Check
Qualify the complete package with the actual product.
Do not approve a seafood can based only on its shape, nominal size, or coating name. The final formulation, fill weight, product arrangement, lid, seam, retort schedule, and shelf life all affect performance.
A can that works with tuna in water may fail with sardines in tomato sauce. A coating that tolerates brine may still show sulfide staining with another fish species. An easy-open end that works before processing may behave differently after retorting.
The package is ready only when the can body, coating, lid, seam, product, and process work together under real production conditions.
Pony Ma | Director ejecutivo
Con 25 años Con experiencia en embalajes metálicos, nos dedicamos a proporcionar soluciones de embalaje sostenibles mediante tecnologías innovadoras de aluminio. Y comparto regularmente información sobre innovación en materiales y estrategias de abastecimiento global para ayudar a las marcas a mantenerse competitivas.
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