Making salted fish is one of the oldest preservation methods in the world, and it requires just two ingredients: fresh fish and salt. The basic process involves coating fish in salt, letting osmosis draw out moisture over days to weeks, then drying the fish until it reaches a texture and salt concentration that keeps it shelf-stable. The details of each step, from choosing the right salt to getting the drying conditions right, determine whether you end up with a delicious preserved fish or a spoiled one.
Why Salt Preserves Fish
When you pack fish in salt, the high salt concentration outside the flesh creates osmotic pressure that pulls water out through the cell walls. As moisture leaves, the fish becomes inhospitable to the bacteria that cause spoilage. Most common spoilage bacteria stop growing once water activity drops below 0.95, and at salt concentrations around 17 to 18 percent of the fish’s weight, very few organisms can survive.
For a shelf-stable product you plan to store at room temperature, the FDA recommends a water phase salt level of at least 20 percent. That means 20 percent of the water remaining in the fish flesh is dissolved salt. For fish you’ll keep refrigerated, a minimum of 5 percent water phase salt is sufficient to inhibit dangerous toxin-producing bacteria. These aren’t arbitrary numbers. They represent the thresholds below which harmful organisms, including the one responsible for botulism, can still grow.
Choosing the Right Salt
Not all salt works equally well for curing fish. The FAO notes that unrefined sea salt and mine salt contain calcium sulfate and magnesium compounds that can cause problems. Too much calcium slows salt penetration into the flesh, which can allow spoilage before the cure takes hold. High magnesium levels produce bitter flavors and can also contribute to spoilage during the salting process.
Your best options are coarse sea salt that has been washed or refined, or plain kosher salt without additives. Avoid table salt with anti-caking agents, which can leave off-flavors. If you’re using unrefined sea salt, taste it first. If it has a noticeable bitter edge, it’s high in magnesium and better suited for cooking than curing. Whatever salt you use, make sure the grain size is medium to coarse. Fine salt dissolves too quickly on the surface and can create an overly salty outer layer before penetrating deeper.
Choosing and Preparing the Fish
Lean, white-fleshed fish like cod, pollock, haddock, and snapper are the traditional choices for salt curing because their low fat content means they dry evenly and store well. Oily fish such as mackerel, herring, and sardines can also be salted, but they have a shorter shelf life due to fat oxidation and require more careful temperature control.
Start with the freshest fish possible. This matters more than you might think. Fish that sit at warm temperatures before salting can develop histamine, a toxin that causes scombroid poisoning. Histamine forms most rapidly between 20°C and 30°C (68°F to 86°F), and once it’s present, no amount of salting, cooking, or freezing will destroy it. Keep your fish on ice or refrigerated below 3.3°C (38°F) from the moment it’s caught until you begin curing. If you’re buying from a market, choose fish that has been properly iced and shows no signs of off-smell or discoloration.
Clean and gut the fish thoroughly. For larger fish, fillet them or split them open (butterfly style) so the salt can reach all the flesh. Leave the skin on to help the fillets hold together during curing. Rinse the fish in cold water, then pat dry before salting.
Dry Salting Method
Dry salting is the simplest approach and the one used for centuries to produce salt cod (bacalao), salt herring, and similar products. You apply salt directly to the fish without any added liquid.
For a heavy cure intended for long-term storage, use a salt-to-fish ratio of roughly 1 part salt to 3 parts fish by weight. That’s about 30 to 35 percent of the fish’s weight in salt. Spread a layer of salt on the bottom of a non-reactive container (food-grade plastic, glass, or stainless steel), lay the fish flesh-side up on the salt, then cover every exposed surface generously. For multiple fillets, stack them with salt between each layer. The fish will release liquid over the first day or two, creating its own brine.
Keep the container refrigerated at around 2 to 4°C (36 to 39°F). Place a plate or cutting board on top of the fish and weight it down with something heavy, like a jar filled with water. The pressure helps expel moisture and ensures even contact with the salt. After 2 to 14 days, depending on the thickness of the fish, the flesh will feel firm throughout rather than soft in the center. Thin fillets from small fish may be fully cured in 2 to 3 days. Thick cod fillets need closer to 10 to 14 days. After 4 to 6 weeks of salt maturation, the flesh typically reaches about 17 to 18 percent salt content and 57 to 58 percent water.
Light Cure for Cooking
If you’re making lightly salted fish to use within a few weeks (kept refrigerated), you can reduce the salt. A ratio of about 3.5 percent of the fillet’s weight in salt, spread evenly across the inner surface, works well for a lighter cure. Let it sit refrigerated for 6 hours or longer. This produces a seasoned, lightly preserved fish rather than a hard-cured, shelf-stable product. It needs to stay refrigerated and should be used relatively quickly.
Brine Salting Method
Brine salting involves submerging fish in a salt-water solution. It produces more even salt distribution than dry salting, especially for irregularly shaped pieces. A saturated brine contains about 357 grams of salt per liter of water, which is roughly 1.5 cups of salt per quart. At this concentration, no more salt will dissolve, and you’ll see crystals settling at the bottom of the container.
To brine fish, dissolve as much salt as possible in cold water, place the prepared fish in the solution, and refrigerate. Make sure all pieces are fully submerged, using a plate or weight to keep them under the surface. Brining times vary: thin fillets may need only 12 to 24 hours, while thick pieces benefit from 2 to 5 days. Some traditional producers combine methods, brining first, then finishing with a layer of dry salt to draw out additional moisture.
Drying After Salting
For a fully preserved product, the salted fish needs to be dried after curing. Rinse the cured fillets briefly in cold water to remove excess surface salt, then pat them dry. The goal is to remove enough moisture that the fish becomes stiff and leathery.
If you’re drying outdoors, choose a period of dry, breezy weather. Hang the fish or lay them on racks in a shaded area with good air circulation. Direct sun can cause uneven drying and fat oxidation. Humidity is your biggest enemy: research from the Canadian Department of Fisheries found that when relative humidity exceeds 50 percent and airflow is low, drying slows dramatically and a slimy surface layer can develop, a sign of bacterial growth. On dry days with low humidity, moderate airflow is sufficient. On more humid days, you need stronger airflow to keep the surface drying fast enough to prevent spoilage.
Indoors, you can use a fan-assisted setup or a food dehydrator set to a low temperature (around 25 to 30°C or 77 to 86°F). Position a fan to blow across the fish at a steady rate. Drying takes anywhere from 3 to 7 days depending on thickness, humidity, and airflow. The fish is done when it’s uniformly stiff, with no soft or moist spots when you press it. A properly dried and salted fish, stored in a cool, dark place at 2 to 4°C, can last at least 2 years.
Common Mistakes to Avoid
- Starting with warm fish. If the fish wasn’t kept cold from catch to cure, histamine may have already formed. No amount of processing removes it.
- Using too little salt. Under-salting is a safety risk, not just a flavor issue. For shelf-stable products, you need that 20 percent water phase salt level. When in doubt, use more salt. You can always soak the fish in fresh water before cooking to reduce saltiness.
- Skipping the weight. Pressing the fish during dry curing ensures even salt contact and speeds moisture removal. Without it, you can get pockets of under-cured flesh.
- Drying in humid conditions without airflow. Sliming on the surface is a clear sign the drying environment is too humid or too still. Move the fish or add ventilation immediately.
- Storing before fully dry. If moisture remains in the center of thick pieces, bacteria can grow from the inside out. Break or cut a test piece to check that it’s dry and firm throughout.
A Note on Long-Term Consumption
Salted fish is a staple in many cuisines around the world, but heavy, lifelong consumption has been linked to increased risk of nasopharyngeal cancer in epidemiological studies. The risk factors that matter most are starting to eat salted fish at a young age, eating it frequently over many years, and preparing it by steaming rather than frying, grilling, or boiling. Occasional consumption as part of a varied diet is a different picture from daily intake stretching back to childhood. If salted fish is a regular part of your diet, varying your preparation methods and balancing it with plenty of vegetables (carrots in particular showed a protective association in one large study) is a reasonable approach.