Salted fish can only be stored satisfactorily in a dry place. Fish which has been cured with impure salt is hygroscopic and will run wet in the store.
This hygroscopic moisture weakens the preserving action of the salt. Fish that has been cured with a pure salt will keep much drier under ordinary storage conditions.
(2) Its Grain. The crystals of Fishery Salt should be coarse and hard. Coarse crystals dissolve slowly, and so produce a more gradual cure than fine-grained salt does. Fine-grained salt extracts the water so rapidly from the surface tissues that it coagulates them. This retards the further penetration of the salt into the fish, so that the fish has the appearance of being slack salted.
Round versus Cleaned Fish. The thoroughness with which a cut fish is cleaned and washed influences the temperature at which the fish can be salted successfully, and materially affects the quality and taste of the product. Tressler[1] has shown that the chief cause of fish spoiling when salted in hot weather is the decomposition of the blood which remains in the flesh. Even in cold weather, it is found that the extra washing and cleaning greatly improve the quality of the fish. As the presence of blood in the fish also leads to discolouration during the salting process, a thoroughly cleaned and washed fish is, after salting, much whiter in appearance and has a finer taste.
Many fish are skinned before they are salted. It has been observed that a skinned fish will cure almost twice as quickly as an unskinned fish. This is because salt penetrates the meat of the fish at approximately twice the rate at which it penetrates the skin. It is desirable, therefore, particularly in hot climates, to skin the fish before salting. This, of course, is only commercially practicable with certain large kinds of fish such as cod.
The Reddening of Salted Fish. Salted fish sometimes undergo a change, either during the salting process if improperly carried out, or more generally in the store, which is characterized by the development on the surface of the fish of irregular red and brown patches. This reddening occurs not only on the fish, but also on the floors and walls of the curing factories, on the sides and decks of fishing boats, and even on the salt itself. It occurs most readily in warm weather.
The reddening has been shown to be due to the growth of a micro-organism (a micro-coccus). With this micro-coccus are generally associated a bacillus and a micro-fungus which produce the brown mould on the fish.
Fish become infected with these micro-organisms by contact with boats or docks or warehouses.
Every precaution should be taken to keep such places clean and properly disinfected.
The “rusting” of fatty fish, e.g. herring, is due to the oxidation of certain free, fatty acids split off from the fats by enzyme action.