ti U. S. BUREAU OF FISHERIES. 



Fisheries indicate that fish preserved in very pure salt soak out in 

 from a third to a half the time required by fish preserved in crude 

 salt. 



What is the practical lesson of this work? It shows that by the 

 judicious selection of salt, not on the basis of its cheapness but on the 

 basis of composition, one can produce a salt fish of almost any 

 desired quality. If salting is to be done in very warm weather it 

 will be necessary to use the purest grade of salt to secure very rapid 

 penetration. In this way a soft, yellowish fish of excellent quality 

 is obtained. Where weather is cool enough to permit, a salt contain- 

 ing more calcium and magnesium may be used, in which case a 

 whiter and firmer fish will be produced. 



Can these very pure salts be obtained commercially? Several 

 brands of salt of the highest degree of purity are available both on 

 the east and west coasts and at a cost not much above the price of 

 cruder salt. In many cases the single item of fish saved that might 

 otherwise spoil will repay the extra cost of pure salt, to say noth- 

 ing of the improvement in quality of the salt fish. 



FLAVORS OF SALT FISH. 



The calcium and magnesium are taken up by the protein in the 

 cells and held, not coming out when the fish is soaked. Now, these 

 impurities, particularly calcium, have an acrid taste and greatly 

 accentuate the " saltiness " of salt. Pure salt is not so " salty " to the 

 taste as crude salt. If the calcium is held by the tissues at the time 

 of soaking out while the salt is removed, then after soaking there is 

 a much greater amount of calcium present in proportion to the 

 amount of sodium than there was in the original salt and a corre- 

 spondingly more acrid "salty" taste. It is therefore necessary to 

 soak out fish much longer or until they are " flat " if they have been 

 cured with crude salt, while with pure salt they may be soaked out 

 until they suit the taste, after which they retain their original flavor. 



Certain improvements in the flavor of fish have been noted after 

 they have been salted by improved methods. The fish variously 

 known as mud shad or gizzard shad {Do7'osoma cepedianum) is 

 plentiful in certain parts of the country but is held in very low esteem 

 because of its muddy, unpleasant flavor. After being washed free 

 from blood and salted in pure salt this unpleasant flavor disap- 

 peared and the fish compared favorably with fish commonly more 

 esteemed. The muddy taste of the carp and other fish from muddy 

 ponds and streams is believed by some to be caused by species of 

 Oscillatoria, a blue-green alga growing in the slime of the fish; by 

 others it is believed to be humic acid derived from the mud. Per- 

 haps the two views could be entirely reconciled, but the actual 

 chemical compound or compounds responsible for the unpleasant 

 flavor seems to be removed by the brine. 



It is not difficult to understand how the alteration of taste may 

 be brought about by salting. The main bulk of the fish, pure protein 

 and pure fat, is believed to be tasteless and odorless. The substances 

 which give rise to taste are free fatty acids (decomposition products 

 from fats), amino acids (decomposition products of proteins), highly 

 odoriferous iiiethylamm^s^ and various waste materials classed by 

 the chemist as purines. The absolute quantities and also the relative 

 proportions of these materials vary from species to species of fish, 



