Reading a Spanish tin: what conservas are, and how they are made

By Porter Lang

Start with the process, because it explains the label. A conserva is seafood that has been cooked, packed in a tin with oil, brine or sauce, sealed and sterilised. The tin is not a way of hiding old fish. An export manager at one Galician cannery put it this way to a food-writing site: “Fresh and canned seafood are not better or worse, they’re different.” He called canning a cooking method.

How the work goes

Culinary Backstreets, a food-writing site, visited two Galician canneries and describes the sequence. Clams, razor clams, cockles and mussels are boiled. Sardines and other fish are slowly toasted in ovens. The cannery’s export head said the toasting is meant “to preserve the texture of the fish”, that it softens the bones so you do not notice them, and that it lets the skin stay on.

The prepared seafood goes into the tin, sometimes within 24 hours of being caught in the case of shellfish, and is topped with brine, olive oil or a house-made sauce. Then the tin is sealed and sterilised. The same article describes a very small cannery with 12 workers where the process is manual, century-old machinery seals the cans, and the labels are applied by hand. Larger canneries, it says, have hundreds of workers and use machines.

For a buyer that gives a practical reading of a label. Ask what the seafood is, what it is packed in, and whether the cannery describes its work as hand-packed. The article says some tins hold seaweed, or shellfish and seaweed together, so the list of possible contents is wider than fish.

Why Galicia

The same article calls Galicia “the Globe’s capital of conservas”, which is its headline claim, not a finding. It gives a layered history, taken from a conversation with the director of the Museo de la Conserva in Vigo. The Basques hunted whales off the Galician coast as early as the Middle Ages. At the end of the eighteenth century Catalans introduced advanced salt-preserving techniques. In 1810, after a request from Napoleon for portable food for armies, the Frenchman Nicolas François Appert introduced preserving in sealed sterile glass jars. Metal cans were created in the United Kingdom. About 30 years later, French entrepreneurs with canning experience began opening factories in Galicia.

The article says growth continued until the 1960s, when freezing and refrigeration cut demand for tinned fish, and that an interest in tuna in the 1970s brought a second wave. Tuna still leads, it says, with sardines, clams, cockles, razor clams, mussels and even sea urchin roe and seaweed also tinned.

Where the shellfish comes from

The magazine describes floating rafts called bateas, in the rías, the river-mouth inlets where fresh and salt water mix. Mussel seed is hung in “socks” on ropes and harvested after eight months. It gives more than 3,000 bateas, producing more than 300,000 tons a year, and says Galicia produces 20 per cent of the world’s mussels, with most exported and the rest going to Galician canneries. Those are the magazine’s figures, and we cannot check them against a second source.

At Carril, it describes shellfish gatherers working individually owned plots on the shore at low tide. Cockles and white clams fetch the highest prices there, it says, while Manila clams, an invasive species, are worth less.

What the museum holds

The Museo de la Conserva in Vigo is run by FUNPROMAR, a non-profit foundation. Its website says the museum’s collection is mostly industrial objects and artefacts covering science, advertising and art, technology, and social and labour aspects. Its archive holds the papers of the former Union of Canned Goods Manufacturers of Galicia, of ANFACO (the trade association) and of a fish-canning firm. We give no practical visiting details.

One region, or several?

Here the sources differ in emphasis. A Montreal retailer’s blog, which sells Spanish foods, says different regions of Spain each have a signature: anchovies from Cantabria, octopus from Galicia, sardines from Andalusia, and white tuna called bonito del norte from the Bay of Biscay. Culinary Backstreets puts Galicia at the centre. Both can be true. Our reading is that Galicia is the largest name and not the only one.

Will a tin improve with age?

A cannery owner told Culinary Backstreets that a tin of seafood “is better after four years”, because the seafood combines with the olive oil. A colleague recalled eating a tin sealed in 1982. That is one producer’s view, repeated by one magazine, and we cannot confirm it, so we would not treat it as a rule. Check any storage guidance printed on the tin itself.

Dates in order

Middle Ages: Basque whaling off Galicia, according to Culinary Backstreets.
Late 18th century: Catalan salting techniques arrive, according to Culinary Backstreets.
1810: Appert’s sealed glass jars, according to Culinary Backstreets.
Around 1840 (our reading of “about 30 years later”): French-run factories open in Galicia.
1960s: demand falls with freezing and refrigeration, according to Culinary Backstreets.
1970s: a second wave, led by tuna, according to Culinary Backstreets.

What kind of sources these are

Culinary Backstreets is a food-writing and food-tour company, and its article was published in June 2023. The Montreal retailer’s blog is promotional. The Museo de la Conserva’s website is the museum’s own account of itself. We found no regulator, trade-body or independent scientific page for this piece, so the figures above rest on one magazine.

Questions a buyer would ask

Is a smaller, slower cannery better? The magazine presents one hand-run cannery proudly, but that is its framing. Does the tin say what the fish was packed in? Look for oil, brine or sauce. We name no brand and give no prices.

What we left out

Brand and producer names, the owners and managers quoted, any figure about daily output, the retailer’s sustainability claims, and any serving or pairing suggestions.

Quick answers

How is tinned seafood in Spain made? According to Culinary Backstreets, shellfish is boiled and sardines are slowly toasted, then packed with oil, brine or sauce, sealed and sterilised.

Why is Galicia known for conservas? The magazine credits a coast rich in seafood, Catalan salting in the 1700s and French-run factories that opened about 30 years after 1810.

Where is the museum of canning? In Vigo, Galicia, according to its own website, and it is run by the FUNPROMAR foundation.

Roam first. Shop later.

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