The sardine was first canned in oil or a tomato sauce at the beginning of the 19th century, when Napoleon came across the need to preserve food. Today, canned sardines are available in whole in oil, fried or smoked, packed in a mustard sauce, or skinned and boned and sold as fillets.
For instance, fresh sardines along with canned sardines and fennel are used for a special pasta sauce that celebrates the feast of Saint Joseph. Using fresh sardines, make the fishmonger scale, gut and debone the fish. In a large nonstick skillet, heat a small amount of olive oil over medium heat. Add chopped onion and garlic and sauté until soft. Add chopped fresh fennel and sauté until golden. Add sardines, tomatoes, golden raisins, pine nuts and salt, and cook until the sauce lightly thickens and the sardines are cooked through and somewhat broken up. Serve with perciatelli or spaghetti.
Canned sardines, often imported from Morocco, are cooked in stews throughout Central Africa.
Here is the recipe of Sardines & Greens Stew.
Ingredients: oil for frying (palm oil is most authentic, but any vegetable oil will do), 1 onion, finely chopped, 1 clove of garlic, minced, one or two ripe tomatoes, chopped (or canned tomatoes, or a tomato sauce or paste), one to two pounds of spinach, cleaned, stems removed or cassava leaves (Feuilles de Manioc), kale, collards, or turnip greens or similar, cleaned, stems removed and parboiled (or some combination of these), salt, black pepper, cayenne pepper or red pepper (to taste), canned sardines (two or three cans).
Preparation: Heat a few spoonfuls of oil in a large saucepan and fry the onion and garlic for a few minutes. Add the spinach (or greens) and fry them at high heat for a few minutes, stirring continually (only a few minutes for spinach, but a few minutes more for the other greens). Stir in the tomatoes (or canned tomatoes with their juice, or a tomato sauce or paste), the salt, pepper and a cup of water. Reduce heat, cover, and allow simmering for twenty minutes or until the greens are nearly tendering. Add the sardines and continue to simmer until the greens are ready to eat.
To prepare canned sardines at home will be not so much time consuming and cheaper than to buy them ready-made at the store. Here is the description of how you can do it.
Canned Sardines (Herring)
Ingredients: Herring, etc. (approximately six inches long), 1-cup water, 3 tbsp mustard, 1 tsp canning salt, 1tsp lemon juice.
Preparation: If you are using herring or other fish that is over 6 inches long, it is best to scale the fish. Remove heads and viscera. Pack the fish into your canning jars. Make a mixture of the following: 1-cup water and 3 tablespoons of mustard. Mix well and pour into the glass jars, containing the fish. Add to each jar 1 teaspoon of canning salt and 1 teaspoon of lemon juice. Cover all of this with the vegetable oil, leaving about 1 inch space from the top of the jar. Cook in a pressure cooker for seventy minutes at 15-pound pressure.
Canned sardines are nutritious and healthy food, since cold-water fish, such as sardines, contain the highest amounts of heart-healthy omega-3 fatty acids, phosphorus, iron, potassium, vitamin B6, niacin, protein and calcium. They do not loose these healthy components in the process of canning.