Curing and Salting
Cooking Skills: Fish and Shellfish 2
Chapter 6 · Curing and Salting
Skill goal
Preserve and flavour fish with salt, sugar, vinegar and time, and do it safely.
Shopping list for this chapter
The basics
Curing is the oldest way to keep fish. Salt draws out water so the flesh firms up and bacteria struggle, while sugar softens the taste and helps the texture. A weight presses it flat, and time does the work. Gravlax (Swedish for buried salmon) is cured in salt, sugar and dill for 24 to 48 hours; pickled herring is held in vinegar and spices; salt cod is dried in salt for days and soaked back to life; potted prawns are sealed under spiced butter.
Curing is not cooking, so the raw-fish rules matter. Gravlax and pickled herring should be made from fish that has been frozen at -20°C for at least 7 days (general guidance, to kill parasites), and are not for pregnant women, young children, the elderly or anyone with a weakened immune system. Raw fish is stored cold and eaten within the days given. Cooking Skills: Fish and Shellfish 1, chapter 8 covers freezing fish well. No wine, beer or spirits are used; vinegar and lemon replace them.
The method
- Freeze the fish first (at least 7 days at -20°C), then defrost it in the fridge.
- Mix the cure (roughly equal parts salt and sugar by weight) and cover every surface.
- Weigh it down with a tray and tins so it gives up water evenly.
- Turn it and baste with the liquid every 12 hours.
- Rinse, pat dry and slice thinly with a long, sharp knife at an angle, keeping everything below 5°C.
| Cure | Fish | Time (approximate) | Keeps (fridge) |
|---|---|---|---|
| Gravlax | Salmon | 36 to 48 hours | Up to 4 days |
| Pickled herring | Herring or mackerel | 24 hours, then pickled | Up to 1 week |
| Salt cod | Cod | 2 days salting, 24 hours soaking | Soaked: eat within 2 days |
| Potted prawns | Cooked brown shrimp | 30 minutes plus setting | Up to 3 days |
Raw cured fish, hot vinegar and allergens
Cured and pickled fish are not cooked: gravlax and pickled herring are cured, not cooked, so they can carry parasites and bacteria. Use fish that has been frozen at -20°C for at least 7 days (general guidance) or that the fishmonger says is sushi grade, keep it below 5°C, and eat it within the stated days. These dishes are not for pregnant women, young children, the elderly or anyone with a weakened immune system.Hot vinegar and brine: hot pickling liquid scalds and the fumes sting your eyes. Pour it carefully with the pan well away from your face, cool it before it goes near the fish, and sterilise jars by washing them in hot soapy water and warming them in the oven.
Raw fish: keep raw fish on its own board and plate, away from food that won't be cooked. Wash your hands, boards and knives in hot soapy water afterwards, and store raw fish on a plate on the bottom shelf of the fridge so it can't drip onto other food.
Allergens: fish is one of the 14 major allergens, and cross-contact is easy: it can pass on boards, oil, tongs and pans. Crustaceans (prawns), molluscs (mussels, scallops), gluten, milk and egg also appear in fish recipes. Always tell guests what is in a dish.
Try it
Level 1 · Start here
Gravlax
The simplest cure there is. A thick centre-cut piece of salmon, covered with an even mix of salt, sugar and plenty of dill, pressed for two days. Slice thinly and serve on rye with a mustard and dill sauce. Use fish that has been frozen for at least 7 days.
Ingredients (8 portions)
- 600 g centre-cut salmon fillet, skin on, previously frozen and defrosted
- 50 g coarse sea salt
- 50 g caster sugar
- 1 tsp crushed white peppercorns
- 1 large bunch fresh dill, chopped
- 4 slices of rye bread, to serve
- Mix the salt, sugar, pepper and dill. Lay the fillet skin-side down on cling film, cover the flesh evenly with the cure and wrap tightly.
- Put in a dish in the fridge, set a tray and two tins on top as a weight, and leave for 36 to 48 hours, turning every 12 hours and basting with the liquid.
- Rinse off the cure, pat dry and slice very thinly at an angle. Eat within about 4 days.
Cured raw fish and allergens
Cured and pickled fish are not cooked: gravlax and pickled herring are cured, not cooked, so they can carry parasites and bacteria. Use fish that has been frozen at -20°C for at least 7 days (general guidance) or that the fishmonger says is sushi grade, keep it below 5°C, and eat it within the stated days. These dishes are not for pregnant women, young children, the elderly or anyone with a weakened immune system.Smoked and oily fish for some people: pregnant women, young children, the elderly and people with weak immune systems are advised to limit oily fish and shark, swordfish and marlin, and to avoid raw or lightly cooked shellfish and, for some, cold-smoked fish. This is general guidance, not medical advice: check current health guidance if it applies to you.
Allergens: fish is one of the 14 major allergens, and cross-contact is easy: it can pass on boards, oil, tongs and pans. Crustaceans (prawns), molluscs (mussels, scallops), gluten, milk and egg also appear in fish recipes. Always tell guests what is in a dish.
Allergens: contains fish and gluten (rye bread).
Level 2 · Pickle
Pickled herring (alcohol-free)
Pickled herring is a Scandinavian standard. Salt the fillets for a few hours, then cover them in a sweet-sour vinegar brine with onion, carrot and spices. It uses no wine. Use fish that has been frozen for at least 7 days, or buy ready-salted herring fillets.
Ingredients (6 portions)
- 500 g herring or mackerel fillets, previously frozen and defrosted
- 2 tbsp coarse sea salt
- 200 ml white wine vinegar
- 200 ml water
- 100 g caster sugar
- 1 onion, thinly sliced
- 1 carrot, thinly sliced
- 2 bay leaves
- 1 tsp mustard seeds
- 6 white peppercorns
- Sprinkle the fillets with the salt, leave in the fridge for 2 hours, then rinse and pat dry. Cut into 3 cm pieces.
- Heat the vinegar, water, sugar, bay, mustard seeds and peppercorns until the sugar dissolves, then cool completely.
- Layer the fish, onion and carrot in a clean jar, cover with the cold brine and refrigerate for 24 hours. Eat within about 1 week.
Cured raw fish, hot vinegar and allergens
Cured and pickled fish are not cooked: gravlax and pickled herring are cured, not cooked, so they can carry parasites and bacteria. Use fish that has been frozen at -20°C for at least 7 days (general guidance) or that the fishmonger says is sushi grade, keep it below 5°C, and eat it within the stated days. These dishes are not for pregnant women, young children, the elderly or anyone with a weakened immune system.Hot vinegar and brine: hot pickling liquid scalds and the fumes sting your eyes. Pour it carefully with the pan well away from your face, cool it before it goes near the fish, and sterilise jars by washing them in hot soapy water and warming them in the oven.
Allergens: fish is one of the 14 major allergens, and cross-contact is easy: it can pass on boards, oil, tongs and pans. Crustaceans (prawns), molluscs (mussels, scallops), gluten, milk and egg also appear in fish recipes. Always tell guests what is in a dish.
Allergens: contains fish, mustard and sulphites (vinegar).
Level 3 · Salt cod
Salt cod and a brandade
Salt cod (dried, salted cod from a good deli) keeps for months. Soak it for 24 hours in cold water, changing the water, then poach and beat it into a creamy brandade with potato, garlic, milk and olive oil. Serve warm with toast.
Ingredients (6 portions)
- 400 g salt cod
- 300 g floury potatoes, peeled
- 250 ml whole milk
- 3 garlic cloves
- 80 ml olive oil, warmed
- 1 lemon, juice
- 1 pinch nutmeg
- Soak the salt cod in cold water for 24 hours in the fridge, changing the water 3 times. Boil the potatoes for 20 minutes and drain.
- Poach the cod and garlic in the milk for 8 to 10 minutes, lift out, flake (no skin or bones) and keep the milk.
- Beat the cod and potato with the warm olive oil, enough milk to make a creamy mash, the lemon juice and nutmeg. Season sparingly, as the cod is salty.
Hot milk, bones and allergens
Hot liquid and steam: hot milk, stock and poaching liquid scald badly and steam burns faster than boiling water. Keep the handle turned in, lift lids away from your face, use a slotted spoon or fish slice over the pan, and never carry a full pan across a busy kitchen.Bones: even fillets can hide thin pin bones. Run a clean finger along the fillet and pull any bones out with tweezers, and warn children and anyone you serve. Whole sardines and mackerel have fine bones that are best taken out.
Allergens: fish is one of the 14 major allergens, and cross-contact is easy: it can pass on boards, oil, tongs and pans. Crustaceans (prawns), molluscs (mussels, scallops), gluten, milk and egg also appear in fish recipes. Always tell guests what is in a dish.
Allergens: contains fish and milk.
Level 3 · Potted
Potted prawns
A British classic: cooked brown shrimp or small prawns warmed through in spiced butter, packed into ramekins and sealed under a layer of clarified butter. Serve with toast and lemon. Because the shellfish is already cooked, this is not a raw dish.
Ingredients (4 portions)
- 200 g cooked peeled brown shrimp or small prawns
- 125 g butter
- 1 pinch ground mace or nutmeg
- 1 pinch cayenne pepper
- 1 lemon, juice
- 4 slices of toast, to serve
- Melt the butter gently, skim the froth, and pour off the clear butter, leaving the milk solids behind. Keep a third of it aside.
- Warm the prawns in the remaining butter with the mace, cayenne and lemon juice for 2 minutes.
- Pack into 4 small ramekins, press flat and pour the reserved clear butter over the top. Chill for 2 hours and eat within 2 to 3 days.
Potted foods, hot butter and allergens
Potted and sealed foods: a layer of butter keeps air out but does not make food safe for long. Keep potted prawns in the fridge below 5°C, eat within 2 to 3 days, and throw them away if the butter looks cloudy or the smell is sour.Shellfish safety: shellfish must be very fresh and cooked until the shells open and the flesh is firm and opaque. Buy from a good fishmonger, keep it cold (below 5°C), cook it the day you buy it, and never eat shellfish that smells strongly of ammonia. Mussels that stay open when tapped before cooking, or stay shut after cooking, must be thrown away.
Shellfish allergens: crustaceans (prawns) and molluscs (mussels, scallops, squid) are major allergens and can cause severe reactions. Cook them with their own board, pan and tools, tell guests clearly, and don't serve them to anyone who is allergic or unsure.
Allergens: contains crustaceans, milk and gluten (toast).
Experiments
Experiment
Salt-to-sugar ratio
Taste.
- Cure two small pieces of salmon, one with equal salt and sugar and one with twice as much salt.
Look for: Equal parts gives a balanced, mild cure; more salt is firmer and saltier, and shrinks the fish more.
Experiment
Weighted or not
Texture.
- Cure two pieces, one under a weight and one without.
Look for: The weighted fish is firm and dense; the unweighted one is softer and cures unevenly.
Experiment
24 or 48 hours
Firmness.
- Slice a piece cured for 24 hours and another for 48.
Look for: At 24 hours it is soft and mildly cured; at 48 it is firmer, saltier and more translucent.
Experiment
Pickled in vinegar or lemon
Sourness.
- Pickle two small portions, one in vinegar brine and one in lemon juice and sugar.
Look for: Vinegar gives a sharp, long-lasting pickle; lemon gives a fresher flavour that keeps for less time.
Tasting notes
| What I tried | Method or amount | What I saw | What I thought | Will I do it again? |
|---|---|---|---|---|
| Gravlax | ||||
| Pickled herring | ||||
| Salt cod and brandade | ||||
| Potted prawns | ||||
| Salt-to-sugar ratio | ||||
| Weighted or not | ||||
| 24 or 48 hours | ||||
| Pickled in vinegar or lemon |
Troubleshooting
| Problem | Likely cause | What to do |
|---|---|---|
| Gravlax too salty | Cured too long or too much salt | Reduce the salt or cure for 36 hours; rinse well |
| Fish slimy | Old fish or warm fridge | Use fresh fish; keep below 5°C |
| Cure is watery | Normal | Baste, turn and keep the dish level |
| Brandade is too salty | Salt cod not soaked enough | Soak longer with more water changes |
| Potted prawns go cloudy | Butter overheated | Warm gently and clarify the butter |
| Pickle too sharp | Too much vinegar | Add more sugar or dilute the brine |
Cured fish, storage and leftovers
Cured and pickled fish are not cooked: gravlax and pickled herring are cured, not cooked, so they can carry parasites and bacteria. Use fish that has been frozen at -20°C for at least 7 days (general guidance) or that the fishmonger says is sushi grade, keep it below 5°C, and eat it within the stated days. These dishes are not for pregnant women, young children, the elderly or anyone with a weakened immune system.Potted and sealed foods: a layer of butter keeps air out but does not make food safe for long. Keep potted prawns in the fridge below 5°C, eat within 2 to 3 days, and throw them away if the butter looks cloudy or the smell is sour.
Leftover fish: cool cooked fish quickly, refrigerate it within 1 to 2 hours, and eat it within about 1 day (2 at most). Reheat only once, until steaming hot all the way through. Do not refreeze fish that was frozen and thawed unless you cook it first.
Checkpoint: can you do this now?
- I know why fish is frozen before curing.
- I can make a salt and sugar cure.
- I can slice cured fish thinly.
- I can pickle fish without alcohol.
- I know who should avoid raw cured fish.
Next chapter
Cooking Skills: Fish and Shellfish 2, chapter 7 is Smoking at Home: hot-smoking on the hob with wood chips or tea.