Page:Principles preservation fish by salt.djvu/24

18 decomposition. So in salt fish the fat is in the presence of moisture and an abundance of enzyme, and the necessary warmth is usually present also, ideal conditions for decomposition. The fat having been split to fatty acid, there are two factors, so far as known–namely, air and light–which promote oxidation.

Some little study has been devoted to the effect of salts, such as sodium chloride and calcium chloride, on the splitting of fats, but not enough is known about the effect of these substances in concentration to be of any assistance. Whether or not bruises have the effect in promoting decomposition of fat that they have in promoting decomposition of protein is not known but would be well worth knowing, and here further investigation is certain to be of value. It is known that much of the fat in living fish is contained within inclosed cells, and that even the fattest fish is not greasy when fresh. But whenever the cells are ruptured by rough handling, decomposition or whatever cause, the oil escapes and is exposed to all the unfavorable influences of enzymes, moisture, air, and light, and the fish becomes greasy; eventually it will become rancid. And, further, oil escaped from the fish, being of a lower specific gravity than brine, at once rises to the top of the barrel and is lost as food.

All sorts of possible preventives of rust are practiced or suggested for practice–such things as impermeable barrels, air-proof covering over the liquid, a reducing substance in the brine to absorb the oxygen, cool, dark storage, and the like. There is, of course, much dissolved oxygen in the juice of the fish and in the brine and also considerable amounts of free oxygen occluded in the cavities of the fish to effect considerable rancidity, even if all outside air is excluded. This dissolved and occluded air can be removed by a vacuum pump, but this has never been tried commercially, so far as the writer is aware. Very little improvement can be expected until the problem has been thoroughly investigated by scientific methods. In the improved technique recommended by the Bureau of Fisheries in Florida complete covering of the salt fish by brine in tight barrels was specified.

If cod and haddock escape rusting because of lack of fat, they are subject to another enemy perhaps as bad, namely, reddening, by which large quantities of cod and haddock are lost every year. For the past three years work has been conducted by the division of scientific inquiry of the Bureau of Fisheries on the causes of reddening and significant results have been obtained. The cause, in general, has been known for many years to be bacteria, but otherwise little has been known of the origin of these bacteria or of their peculiarities.

Briefly stated, the results of the work cited are as follows: The bacteria that cause reddening are of two distinct kinds–a spirochaete, which in colonies is pale pink, and a bacillus whose colonies are deep red. The two organisms grow in such close harmony that mixed colonies occur which vary in color from pale pink to deep crimson as the proportions of the two organisms present vary. The evidence points to the solor sea salts from the tropical and subtropical seas as the source of the infection. Solar sea salts, both American and foreign, are infected. Mined salts seem to be free from the infection.