Page:Principles preservation fish by salt.djvu/14

8 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 containing 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 nothing of the improvement in quality of the 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 correspondingly 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 (Dorosoma 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 disappeared 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. Perhaps 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 methylamines, 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,