Pickling food sous vide is particularly good as the flavour of the pickle is much more quickly absorbed by the food and the quantity of pickle liquid needed is much less than in conventional methods. Mackerel lends itself particularly well to pickling as the flavour of the fish is strong enough to stand up to that of the vinegar and any other complementary flavours that may be added.
Mix together the vinegar, water, sugar and salt and stir until the salt and sugar have dissolved
Place the mackerel fillets flat in a vacuum bag ensuring that they are not overlapping and seal
Transfer to the fridge for 30 minutes then remove the fish from the bag and pat dry
The mackerel can be kept for up to 3 days once pickled
If you prefer the fish to be pickled further, leave it in the bag longer.
The pickle can be flavoured with various herbs and spices, such as coriander seeds, peppercorns, garlic, bay leaf and thyme. You could also try adding a little horseradish or chilli to the pickle for a bit of a kick.
To add colour to the fish, substitute the water for beetroot juice.