FISH CURING, an operation, or series of operations, the object of which is the preservation of the flesh of fish by salting, drying, pickling, or smoking. Though preservation by various means in periods of plenty against periods when fish could not be caught has been practised tby man since earliest times, it is only recently that a scientific study of the various processes has been begun and the literature is still of meagre character. Curers, in consequence, rely for results on experience and rule of thumb practices, passed on traditionally from father to son.
The principle involved in salting is one of osmosis, in which a certain amount of salt combines with the water of which the tissues of fish flesh are largely composed. Subsequently the com pletion of curing may be accomplished by allowing the fish to remain in the salt solution (pickle) of its own creation, as in the case of pickled herrings, sprats, mackerel and salmon; or it may be dried in the sun, or by artificial heat as in the case of salt cod; or smoked, as with red herring.
As civilization has advanced, there has been a tendency in the temperate zones and in regions touched by increasingly rapid transport for the harder cures to be replaced by fresh fish or by more lightly cured preparations, and for the hard cures (cod, ling, saithe or coalfish, haddock) thus superseded to find new markets in less readily accessible parts of the world among more primitive peoples. Thus in the years immediately preceding the World War Germany was taking a steadily increasing volume of fresh herrings but at the same time the quantity being cured was growing be cause pickled herrings were penetrating further and further into Russia. Similarly, hard cures of cod (also ling, haddock, coalfish and tusk) were being marketed in tropical Africa, Central and South America, experience showing it to be a simpler matter to cure fish in Arctic Norway, at British ports or in Newfoundland for such markets than it is to catch and cure indigenous fish on the spot.
Later developments of the same general tendency have been that with the improvements in refrigeration, cold stored fish begins to compete with cured fish. Of this it is too early to speak, except to state that it has been demonstrated that cold-stored fish can be more widely distributed geographically than was possible with salt cured fish 5o years ago. As a result of improvements in re frigeration at least one fish, the hake, has disappeared from among the kinds which were formerly cured.
Heavy curing of fish was essential in the early days of civiliza tion in northern latitudes when fish flesh had of necessity to take an important place in human fare. With regular supplies of fish available lighter cures have come into use in which the process of smoking is more largely concerned than that of salting. Among these are kippers and bloaters, as split and round herrings are termed respectively, smoked haddock (finnan), whiting and cod ling. In the case of the last three the fish are headed and split after the manner of cod, except that the backbone is not removed. All these are in popular demand in Great Britain, but in the last few years remarkable developments have followed the introduc= tion of smoked fillets. For the preparation of these boneless strips are cut from such fish as cod, ling, haddock, tusk. Before smok ing these are steeped in a pickle to which a harmless vegetable dye (annatto) is customarily added. An economical and readily transported product is then available which has met with a keen demand not only at home but in British colonies.
In Great Britain, the United States, Norway, Holland and Russia cold-smoking is customary, but in Germany and Sweden hot-smoking, by which the fish is partially cooked whilst being smoked, is favoured.
In the British Isles the curing of herrings is done ashore and a Government brand can be demanded guaranteeing the quality and preparation of the contents of the barrels branded. Dutch, Ger man and French fishermen cure their herrings aboard their ships at sea.
Cod are cured both at sea and ashore, but the final stages of preparation for export are completed ashore. At sea, on the Ice landic fishing grounds in spring, trawlers belonging chiefly to England, Germany and Iceland concentrate on the cod fishery. French trawlers favour more the Newfoundland Banks. When the fish are to be cured at sea they are eviscerated, headed, about two thirds of the backbone removed, and then thoroughly washed. After this they are stacked in the trawler's hold with salt in plenty between the layers of fish. Sale is by contract or by auction at a price per ton.
It is customary for British vessels proceeding on "salting voy ages" to engage Scandinavian "splitters" for the specialized work implied by the word. Machines have recently been devised in Ger many which do this work very effectively, and these have also been fitted in ships.
After the fish has been landed at Aberdeen, Hull or Grimsby the process of curing is completed at "cod farms," where the fish are spread on racks exposed to the sun or dried under cover by air heated by coke fires or other means. When the desired standard of dryness has been attained the fish are packed in cases which for some markets are tin lined and hermetically sealed. Large quantities of fish, cleaned at sea and brought ashore in ice in the customary manner of all white fish, are split, salted and dried in establishments in the manner described above. The curing of ling, coalfish, haddock, tusk, is of minor importance and occurs when these fish are incidental to the cod fishery. Curers of salt fish have constantly to be on their guard against "pink-eye" in their stocks. This is caused by organisms occurring in unsterilized salt which develop under certain conditions of temperature and moisture and, giving the fish a pink appearance, render it unsalable. The chief markets for salt cod are the Roman Catholic countries of South ern Europe (Spain, Portugal, Italy), and of South America (Argentine, Brazil, Uruguay) and the West Indies. The lower grades are also extensively exported to West Africa.
BIBLIOGRAPHY.—"Viking," "The Art of Fish Curing," Fish Trades Bibliography.—"Viking," "The Art of Fish Curing," Fish Trades Gazette (5906), a detailed account of the methods employed in Scotland and England ; D. K. Tressler, Marine Products of Commerce (1923). The results of investigations into various matters affecting fish curing are contained in publications by the following: Director of Fisheries, Bergen; U.S.A. Bureau of Fisheries, Washington; Dept. of Scientific and Industrial Research, London; Fishery Board for Scot land, Edinburgh ; Ministry of Agric. and Fisheries, London ; Dept. of Agric. and Technical Instruction for Ireland, Dublin; Biological Board for Canada, Ottawa ; German Sea Fisheries Society, Berlin ; Sea Fisheries Institute, Wesermunde ; Imperial Fisheries Institute, Tokyo.