Harden Franklin Taylor

“ The agency which breaks down protein into these simpler substances is called an enzyme, and protein must always be so liquefied or digested by enzymes before it can be absorbed through membranes; hence the necessity of digestion in the stomach of animals preparatory to absorption of food through the intestines. Now, animals, including fish, require a certain amount of new protein to support the body activities, which, failing, the animal would immediately perish. But the hazards in the existence of any animal often make it obligatory to do without food for a shorter or longer period. ”

“ Once the permeability of cells has been increased by abnormally high or low temperature, does this increased permeability persist after a normal temperature has been restored? When autolysis is set in action by a bruise, do autolytic enzymes affect only the part bruised or do they escape and attack the uninjured cells, destroying them also? To what extent does the acid of rigor mortis accelerate autolysis, and can this acceleration be prevented by early application of salt? To what extent is loss of soluble material in brine due to rough handling and to what extent to other factors? ”

“ Every species of bacteria is acclimated to some particular set of conditions, some of them almost incredible for living things. These red bacteria are accustomed to live and grow either on moist salt or very strong salt solutions. If bacteria are particularly resistant to some condition, as to strong salt in this case, it does not follow that they are likewise resistant to all severe conditions. It is the bacteriologist's business, by studying all the habits and peculiarities of the organism, to discover its weakest point where attack will destroy it. ”

“ In the case of mackerel and herring and such other fishes as have fat tissues the fish must at all times be carefully excluded from contact with air. If the fish are directly exposed to air for a time, the fish "rust"–that is, the fat becomes reddened and rancid–and the value of the fish for food is very greatly impaired. This rusting, especially of salt mackerel, is of immediate and pressing practical importance, for there is a regular waste of a large percentage of mackerel on our northeastern coast for no other cause than rustiness and rancidity. ”

“ Salt arrests autolysis when it arrives, but considerable damage may be done before the salt has reached the innermost parts of the fish. Now, these two processes—salt penetration and autolysis–are running a race, so to say. If the salt penetrates to the innermost parts before autolysis has destroyed them, the salt wins the race and the fish is saved. If before the salt can get to the innermost parts they have been decomposed by autolysis to an intolerable degree, then autolysis wins and the fish spoils. ”

“ 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 ”

“ So there is in each cell stored along with the protein some enzyme ready in case of threatened starvation to break the protein down into simpler substances which penetrate outward into the blood for transportation to the point of need. Fish may thus live for a time at the expense of their own bodies.
These enzymes, present in every part of the fish, while almost an absolute necessity to the living fish, become the greatest enemy of the dead fish, for they soften and liquefy the cell contents, cause unpleasant tastes and odors, and permit the contents to escape from, the cell into brine. ”

“ The bacteria are adjusted to strong salt solutions, that is, the body fluid is of such concentration and their covering membrane is of such partial permeability that when surrounded by strong salt solution they live normally, but when water or weak brine surrounds them these relations are disturbed and they die. Probably water enters the cell in excessive quantity. It is known that the reddening does not attack fat fish. Perhaps the fat acts directly on the membrane, or indirectly by acting on the calcium and magnesium in the salt, to effect the disturbance. ”

“ The distribution of fat is also different in different species of fish. Some fishes, such as herring, salmon, and alewives, contain fat well distributed throughout the body tissues. In others, such as cod and haddock, the fat is localized in some particular part of the body, as in the species mentioned the oil is contained in the lever, the flesh being almost entirely destitute of oil. For reasons that will be set forth later fat fish must not be exposed to the air because of untoward changes that air causes in the fat; but no harm is done to the protein constituents. ”

“ But many of the free fatty acids of fish oils readily oxidize on exposure to air and light, developing during the process a darker color and an unpleasant odor and taste which we call rancidity. Once fats have become rancid they can never be restored to their original sweetness.
What conditions promote rancidity? First, the fat must be decomposed or "split" into glycerin and free fatty acid. Next it must oxidize. Just as fish contain autolytic enzymes that decompose protein, so they also contain fat-splitting enzymes. These enzymes require moisture and warmth for their activities. ”

“ Fat that has been removed from the tissue that produced it may be kept under proper condition for a long time, because only a small amount of fat-splitting enzyme goes with the oil, but when the fat is not removed from the original source all the enzyme is present and available to produce 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. ”

“ It is of the greatest importance that research work be undertaken for the purpose of discovering the conditions under which the cell proteins are digested and pass out and for ascertaining the conditions under which these processes may be arrested. ”

“ The tissues of fish consist mostly of cells. Each cell is a bag of semiliquid, like the white of egg. The surface of every cell either is or acts like a semipermeable membrane. If we surround the cell with water, the inside will be more concentrated than the outside and water will go in. If we surround the cell with strong salt solution, water will pass out to the salt. Some salt will also pass into the cell, which fact shows that the cell wall is not ideally semipermeable. ”

“ If the stomach became empty because of temporary shortage of food or an injured mouth, the animal would die unless special provision were made to supply protein from some other source. But nature has provided a means whereby the proteins in the less important parts of the body can be used for the time being to support the activities of the absolutely necessary vital parts. The stored protein is within cells and could not possibly be carried by the blood stream to the point of need unless it could get out. ”

“ There are reasons for expecting that the improvements made in the salting of other fish, particularly those which depend on the use of a very pure salt, will find application in the mild curing of salmon.
14. Fats undergo certain changes after the fish is salted, resulting in a condition known as "rusting." Rusting consists of oxidation of fat after the latter has been split into free fatty acids. This splitting is caused by tissue enzymes in the presence of warmth and moisture. Oxidation is brought about through the agency of light in the presence of water. ”

“ The removal of water by means of salt is in some senses a truer dehydration than actual drying in air, for changes of an undesirable sort take place in air drying that are never corrected, while salting may be done in such a way that few changes other than removal of water are brought about. The statement that salt preserves by extracting water is to be taken strictly and literally, for salt has no peculiar preserving or antiseptic quality, as many people seem to think. ”

“ We have then by exposing the fish to water put water back in the cells and taken out the excess salt. The actual food material of the fish–the cell protein–is still where it was, for practical purposes unchanged. If every step has been scientifically correct we have at the end very nearly the fresh fish we had to start with. But there is the rub. At every turn it is possible to depart from the scientifically correct. The principles of osmosis here very briefly stated are the fundamentals of the art of salting fish. In all that follows there will be frequent occasion to refer to osmosis. ”

“ It is, however, a common experience in pickling fish that the warmer the temperature the more rapid the striking through, a difference too great to be accounted for by temperature variations of osmotic pressure. The cell membrane itself must change. Whether any more free permeability caused by warm temperature is permanent after the fish is chilled again is not known, but the question would be well worth investigating. Cold, when in the neighborhood of freezing, also promotes permeability, as has been proved by various experiments. ”

“ A method of promoting the preservation of fish by salt by the aid of sodium hypochlorite along with the salt has been patented. The original idea, it is understood, was to decompose the salt in sea water by electrolysis, sodium hypochlorite being formed. It was claimed that the sodium hypochlorite penetrates faster than ordinary salt. This substance contains some oxygen that may be given off to act as a sterilizing agent, and after the oxygen is given off ordinary salt or sodium chloride remains. ”

“ If the membrane is perfectly permeable to all constituents, water will pass through to the salt solution and salt will pass through to the water, and these movements will continue until the two sides are alike and then stop. It is always the tendency for the two liquids to come to equilibrium, and they would do so if the membrane were perfectly permeable. ”

“ The climate is excessively warm, and there is an abundance of fish (alewives) adapted to preservation by pickling in a region where an industry might well be built up and where repeated efforts to salt fish in the past had failed. Accordingly, the interest of local fishermen and dealers was enlisted to cooperate in the undertaking, and an experienced fish packer from the Chesapeake Bay region was sent to Florida, after he had been thoroughly instructed in the technology of the process, to try salting by the proposed method on a small commercial scale. ”

“ It may be admitted readily that science has not so pervaded and dominated the fish-pickling industry as it has other ancient arts, but it has contributed something and is capable of contributing a great deal more, and here lies the purpose of this paper. That purpose is to present the rationale of salting and pickling fish, so that the reasons for the various steps and modifications will be readily understood and appreciated, to the end that the art may be practiced more intelligently and successfully. ”

“ 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. ”

“ Fish that have been held a long time are soft and of a disagreeable odor, because autolysis and possibly some bacteria have decomposed the tissues to some extent.
One might reasonably expect research to show that if rapid penetration is secured by means of pure salt the amino acids and other sour or disagreeable substances in stale fish resulting from autolysis would be removed by changing brine a few times, leaving the fish in a condition quite wholesome and fit for food. ”

“ By osmosis oxygen is taken from the air into the blood without any leakage of blood. By the same principle the kidney tubules remove undesirable substances from the body while holding back all desirable substances. By osmosis the roots of plants select the necessary minerals from the soil. A weak sugar solution will readily ferment, but if made concentrated it destroys yeast and bacteria by osmosis and is therefore an excellent preservative of fruits. Salt is also a preservative by virtue of its concentration. ”

“ The optimum temperature for autolytic activity is about human body temperature, 98° F. The autolytic enzymes act under a slightly acid condition. In neutral or alkaline medium they act very little, if at all. It has been noticed by various investigators that autolysis does not begin until two to four hours after death. During rigor mortis there is a decided development of acid that may very materially promote autolysis. It may therefore be that salting fish immediately after capture would strike through the fish before autolysis gains any headway. ”

“ Not only does quite pure salt penetrate the fish more rapidly, but when the time comes to cook the fish it is found to soak out more rapidly also. Practical experiments in the experimental kitchen of the Bureau of 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. ”

“ It is not mere guessing to say that when advantage is taken of all that is known of improved salting methods a fish nearly if not quite equal in edible qualities to fresh fish is obtained, and in some cases the quality is decidedly improved by salting. ”

“ While the former white. firm fish is the customary quality demanded in commerce, there are strong reasons for believing the softer and yellowish fish produced in pure salt to be superior. There is reason for believing that the whitening of the fish in impure salt is explained by the fact that the calcium coagulates the protein, just as heat by coagulating egg white causes it to be white and firm. But where there is no calcium in the salt the protein retains its natural translucency and yellowish color. ”