Fish should be prepared immediately after the catch. When you catch fish, handle them with care to avoid bruising. Beware that exposure to the sun or heat may cause the quality of the fish to deteriorate. Bleed fish immediately after catching to increase the storage life. Remove internal organs and rinse the fish inside and out. Keep fish iced, refrigerated, or frozen until ready to process. Keep fish between 32-40° F (0-4° C) for no longer than one to two days.
You can use either fresh fish or frozen fish for pressure canning. Many Alaskans freeze their catch for up to one year. When fishing season arrives again the fish remaining in the freezer are canned. This gives the fish an effective shelf life of two years. When using frozen fish thaw it in the refrigerator or place the wrapped fish under cold, running water.
There is little we can do to control the composition of the fish flesh as in most cases fish are harvested wild. The living fish flesh is bacteria free. Bacteria is present on the skin, gills, and in the viscera, however, they cannot penetrate the flesh while the fish is alive. The fish flesh becomes contaminated with bacteria during handling and preparation. The sooner the fish can be processed the smaller the number of microorganisms it will contain. Poor quality fish that has been invaded by microorganisms can be characterized by the presence of slime, discoloration of the gills and eyes and loss of flesh texture. To minimize microbial contamination, the fish surface must be scrupulously washed, gutted and rinsed inside. The gills must always be removed. The fish that will be canned must have the scales removed. The scales will fly everywhere so it is wiser to perform this operation outside. After cleaning, the fish has to be washed again. Previously frozen fish can be thawed, then brined and smoked.
Lobster and crab spoil very quickly after death. For this reason lobsters and some crabs are cooked alive in boiling water or weak brine (3-5%) to inactivate enzyme activity.
Shrimp can be cooked and peeled, or peeled raw and then cooked to harden the texture and cause the shrimp to curl. Oysters and clams often contain mud or sand on the exterior and should be well washed before opened. Precooking in boiling water kills the animal, opens the shell and firms the meat.
There are circumstances in which a canner will select a process which is more severe than that required for commercial sterility, as for instance occurs when bone softening is required with salmon or mackerel. Large fish are precooked whole in a steam kettle or cut into sections and precooked in brine.
Small fish are precooked in steam which removes moisture and oil that otherwise will be released in the container during thermal processing. That would adversely affect the texture, appearance and flavor of the product. This cooked out liquid should be drained away.
Precooked fish should be cooled as fast as possible to firm up the flesh to prevent breaking up the flesh during packing into the containers. The packing should follow immediately after.
Fish will benefit from immersing them in a strong brine (80 salinometer degrees), even for a short time. This toughens the surface of the flesh and removes traces of blood. The whole fish may be brined for 45 minutes, small fish or fillets for 5-15 minutes.
Fish like other meats can be smoked by different smoking methods. Smoke temperature and the length of smoking will influence the taste of the fish. All fish may be smoked, but the fatty ones absorb smoke better, stay moister during smoking and taste better.
Salt, spices and condiments will improve flavor. Oil, brine, tomato juice, water or sauces improve appearance and flavor and enhance the heat penetration during thermal processing.
Commercially canned fish is packed tightly to prevent it from shaking around and breaking into small pieces. It is also weighed to meet the requirements on the label. Fish that is processed at home must be cut in a way to best utilize the height of the container. Fillets can be rolled around the can, the shorter ones going inside the can. That is why the 307 x 22.25 can is so well adapted to canning fish.
The tall salmon can, 301 x 408, is another can that is great for canning a variety of fish. Both of those 2-piece cans are tapered which makes them especially attractive for storing at home as they nest inside each other.
Fish packed in jars should be neatly arranged to take advantage of the display properties of the glass, however, due to the shape of a glass jar it is harder to neatly remove the delicate product.