A member of the mackerel family, tuna are mainly found in the world's warmer oceans. They can grow to a huge size (up to 700kg) and their meaty flesh is distinctively flaky and firm with a rich, strong flavour, the consequence of its comparatively high oil content. Tuna is mainly sold as steaks. It dries out quite quickly, so should be cooked very briefly over a high heat; marinated before cooking; or simmered in a sauce.
There are many different varieties of tuna but, largely as a consequence of prolonged overfishing, only a handful of these are commercially available - and most of those that are available are considered to be endangered to the point of extinction (Mediterranean and Atlantic) or in decline, particularly bluefin.
Choose the best
As tuna are oily, they go off quickly, so need to be very fresh. When buying tuna steaks, look for those that have been trimmed neatly, with firm, dense red or dark red flesh and a meaty aroma.
Avoid those with strong discolouration around the bone, or which have a dull, brownish cast. Thicker-cut steaks will stay juicier during the cooking process.
Among the best types of tuna are bluefin (which is particularly highly prized and also endangered, so think carefully before you buy), yellowfin, and albacore. Bonito, which falls into a category somewhere between tuna and mackerel, but which is generally classed as a tuna, is also highly sought-after.
Tuna is also available tinned. Albacore is one of the best types sold this way. Skipjack (which, like bonito, is a somewhere between tuna and mackerel, but classed as a tuna) is the most commonly tinned variety. Tinned tuna is available packed in water, brine, vegetable oil or olive oil (with the last being the best).
While it's important to make sure that your tinned tuna is marked as 'dolphin friendly' (which means that it was caught by line rather than by net, in which dolphins and other marine life can become tangled up) or even 'bird friendly' (unless tuna fishing lines are tagged with coloured 'scare tapes', birds fail to spot them and can become trapped), it's equally as important to see whether the tuna is bluefin, yellowfin, albacore or skipjack.
To find out more about many types of endangered fish, try reading The End of the Line, by Charles Clover.
Tuna steaks should not be washed before cooking - just pat them dry with some kitchen paper. Tinned tuna should be drained before use.
For fresh tuna, remove any packaging, wipe with kitchen paper, put on a plate, then cover with clingfilm and put on the bottom shelf of the fridge. Consume within a day. Tinned tuna should be stored in a cool, dark place. After opening, it should be transferred to a non-metal, airtight container and kept in the fridge for up to 24 hours.
Barbecue, grill or pan fry (up to 2 minutes each side). Bake, wrapped in oiled foil (10-15 minutes). Braise (10-15 minutes).
Try herring, tilapia or mackerel.