THE PRINCIPLES OF FISH SALTING 363 



loses its brilliant red color, and the tissues become soft. When these changes 

 have reached the point where odor and taste have become objectionable, the fish 

 is said to be spoiled. The presence of more than 4 per cent of salt in the solutions 

 in the tissues of the fish retards both autolytic and bacterial decompositions and, 

 when the amount of salt in the solution in the fish reaches 20 per cent, the 

 decompositions proceed so slowly that there is little danger of spoilage, except 

 through prolonged storage at elevated temperatures. During salting autolysis and 

 bacterial action tend towards the decomposition of the fish while the passage 

 of the salt into the tissues and the water out into the brine, retard these processes 

 of decomposition. If, before they become too stale, the fish are placed in brine or 

 salt during cool weather, they "strike through" before they spoil; but if the salting 

 takes place at such elevated temperatures that the decompositions proceed more 

 rapidly than the salting, the fish spoil. 



The Influence of the Composition of Salt 



The composition of the salt used has been found by Tressler (1920) to be of 

 great importance, not only in affecting the rate of its penetration into the tissues 

 of the fish, but also in determining the physical qualities of the product. The chief 

 impurities in commercial salt are calcium salts, magnesium salts, sulfates, and 

 organic matter. Sea salts are almost universally used for the salting of fish. The 

 composition of a number of samples collected from various parts of the world 

 are given in Table 6 (p. 15). From these data it is seen that these salts are, 

 for the most part, high in calcium and magnesium salts and sulfates. Turks' Island 

 and Trapani salts, which are used in large quantities by the fish salters of the 

 Atlantic Coast, are particularly high in magnesium salts. 



Calcium and magnesium salts and all sulfates effect a retardation of the rate 

 of penetration of sodium chloride (salt) into fish during the salting process. This 

 retardation of the rate of salting permits more decomposition of the protein of 

 the fish tissues during the process of salting. Therefore, it is important to use nearly 

 pure salt when stale fish are to be salted or when the salting process takes place 

 under adverse conditions, such as in warm climates. Calcium salts retard penetra- 

 tion of salt into fish to a greater extent than either magnesium salts or sulfates 

 and are, therefore, objectionable if present in appreciable amounts. Sulfates are 

 seldom present in sufficient quantities to be objectionable. 



Calcium and magnesium salts, present as impurities in salt used for the salting 

 of fish, affect the color and firmness of the product to a remarkable extent. Fish 

 salted with pure salt are soft, flabby, and of a very light yellow or cream color. 

 Such fish are easily freshened and, when cooked, closely resemble fresh fish; they 

 possess few of the qualities commonly associated with salted fish. The presence of 

 as small an amount as 1 per cent of calcium or magnesium in salt causes a re- 

 markable whitening and stiffening of the flesh. Salts of both of these metals give 

 a strong, bitter taste, characteristic of commercial salted fish. By varying the 

 proportion of calcium chloride in common salt from to 5 per cent salted fish can 

 be prepared of any desired shade, from pale yellow to snowy, chalky whiteness. 

 This should be of considerable value to the fish Salter, for it enables him to con- 

 trol the color and character of his product. Salt containing as much as 2 per cent 

 calcium as calcium chloride produces very stiff, brittle fish, quite unlike fresh fish; 

 a like amount of magnesium chloride or sulfate produces a similar though slightly 



