From the Sea to the Tin: How Sardines Are Actually Canned

Station 1 — The night hunt

Sardines school densely and rise toward the surface after dark, so the fleets go out at night. The classic method is the purse seine — a wall of net drawn around a school and cinched shut at the bottom like a drawstring purse — and many fisheries use lights to gather the shoal first. The moment the net closes, a clock starts that governs everything downstream: oily fish degrade in hours, not days. Chilled seawater holds the catch on the run home, and the best houses — Galicia's old rule especially — want the fish landed and processed the same day it's caught.

This is also why season matters. A sardine's fat content peaks in the warm months, which is exactly why the Mediterranean and Atlantic festival season and the canning season are the same season — the fish is at its richest. (Our live Season Watch tracks where sardines are running now.)

Station 2 — Landing, grading, brine

At the quay the catch is landed and sold, then graded by size — and this is a detail that quietly explains pricing. Tins are built to the fish: the smallest, most delicate sardines ("sardinillas") are counted into premium tins by the dozen, which is why they cost more than a standard pack. Graded fish then go into a brine bath, where salt does three jobs at once — it firms the flesh, seasons it, and begins drawing out moisture so the final pack isn't watery. The UN's FAO fish-canning guidance is the citable backbone for this and the stations that follow.

Station 3 — Nobbing and the haircut

Next the fish are cleaned: heads and guts removed — the trade calls it "nobbing" — and tails trimmed. In artisanal houses this is still done by hand, at a speed and delicacy machines have never matched for a fish this fragile. It's the single most visible difference between a hand-finished Portuguese or Galician tin — fish neat and intact, silver skins aligned — and a machine-processed budget pack where the pieces arrive broken.

Station 4 — The cook: steam vs. fry, raw-pack vs. pre-cook

There are two traditions here. In the pre-cooked method — the Iberian classic — the fish are steamed or blanched on racks and drained before they go in the tin. In the raw-packed method — common for Nordic brisling styles — the fish are packed raw and cooked inside the sealed can during sterilization. Either way, a sardine is cooked once, before or during the process; a "fresh-packed" tin simply means the fish cooks in its own sealed tin. The older Portuguese habit of frying the fish in olive oil before packing lives in this station too — a step you can still taste in some traditional tins.

Station 5 — Hand-packing: the human minute

This is the signature image of the whole industry: rows of packers laying fish into tins by hand, belly-up or belly-down, in patterns that haven't changed in a century. Why do hands still win, in an age that automates almost everything? Because cooked sardines are fragile, the tolerance on fill weight is tight, and the way the fish are arranged has to survive all the way to your plate. A machine can't yet do all three at once for a fish this soft.

Station 6 — Oil, sauce, and the double seam

Now the tin is filled — with olive oil, another oil, brine, or a sauce. Oil grade genuinely matters, and it's a big part of why a good tin costs more. Then comes the step that is, quietly, the entire food-safety story of canning: the double seam. The lid and the body of the can are rolled together in two operations into five interlocked layers of metal with a sealing compound — no glue, no weld, just precisely folded steel or aluminium and a gasket. A vacuum is drawn as it closes, which is why the ends of a good tin pull slightly concave — and why a bulging tin is a warning you should never ignore.

Station 7 — The retort: why a tin needs no fridge

The sealed tins are then pressure-cooked in a retort at roughly 115–121°C, long enough to render the contents commercially sterile — the standard that guarantees no Clostridium botulinum can survive. This single step is the reason a sardine tin outlives every other fish product in the shop: fully sealed and fully sterilized, it's safe at room temperature for years. No fridge, no preservatives beyond salt and oil — just physics.

Station 8 — Rest, age, dress

The best houses don't ship immediately. They rest the tins for weeks or months so the flavours marry in the oil — the reason a "vintage" tin (millésimée) exists at all, and improves with keeping like wine. Finally, the dress: can lithography, ink printed onto flat tinplate before the metal is formed, a craft with a 150-year history that turned Portuguese and Breton tins into collectibles. The artisanal flex is the wrapped-paper tin — Nuri's are still hand-wrapped, one at a time. It closes the loop nicely: the art on the tin is the last station of a process that began with lights on dark water.

What you're actually paying for

Run the stations back and the price of a good tin stops looking mysterious: a same-day night catch, size-grading, hand-nobbing, a careful cook, the human minute of hand-packing, real olive oil, a five-layer seam, a sterilizing retort, and months of patient resting before the lithographed lid ever meets a shelf. "Just canned fish" is the least accurate description in the grocery store.

See where all that craft lands in the full ranking, browse the makers on the Canneries & Makers page, or explore the whole brand directory.

Frequently asked questions

How are sardines caught for canning?

Mostly at night with purse-seine nets around dense schools, often aided by lights; they're chilled immediately and ideally canned within a day, because oily fish spoil in hours, not days.

Are sardines cooked before they're canned?

Yes — either pre-cooked (steamed) before packing or cooked inside the sealed can; all tins are then pressure-sterilized in a retort.

Why are sardines still packed by hand?

Cooked sardines are fragile and tins are graded to fish size; hands beat machines on breakage, fill accuracy and presentation, which is why premium Portuguese and Galician canneries still employ rows of skilled packers.

How is a sardine tin sealed?

With a double seam: the lid and body edges are rolled into five interlocking metal layers with a sealing gasket, then vacuum-sealed — no glue or welding.

Why don't canned sardines need refrigeration?

Retort sterilization (~115–121°C under pressure) makes the sealed tin commercially sterile, safe at room temperature for years — and many tins genuinely improve with age in oil.