Page:Principles preservation fish by salt.djvu/16

10 It is seen that the brine-salted fish consistently undergo a greater decomposition than those salted with dry salt, as shown by the abundance of decomposition products, amino acids. The average excess of amino acid nitrogen in the six lots pickled in brine over the six lots in dry salt is 51 per cent, a very material difference. It will be noticed in the last column of the table that spoiling of fish pickled in brine takes place at a lower temperature than it does in dry salt. Fish were satisfactorily salted in dry salt at 80° F., but at this temperature fish pickled in brine spoiled.

To complete the evidence in favor of using dry salt, the following table from the, same paper shows the rate of penetration of salt into squeteague when applied dry in comparison with brine:

What is the reason for the superiority of dry salt over strong brine or pickle, especially since the dry salt very shortly forms its own pickle? In answer to this question it is necessary to refer to the principles of osmosis. It was shown that the flow of water is from the less concentrated to the more concentrated. The relative concentrations govern the direction of flow and also the rate or quantity of flow. Salt is going into the fish and water coming out. If brine is used, it is losing some of its salt which penetrates the fish and is being diluted with water which is coming out. This process rapidly brings the contents of the cells into equilibrium with the brine; that is, with the film of brine immediately in contact with the fish. Stirring as usually done may cause a momentary increase of penetration by removing the film of dilute brine adjacent to the fish, but we may imagine that a new dilute, film forms again very rapidly. If instead of brine dry salt is placed in contact with the fish very material differences are at once apparent. Part of the salt dissolving in the free moisture forms strong brine, which begins its extraction of water from the fish. The water coming from the fish is not able to dilute the adjacent brine, because some of the excess of dry salt present immediately dissolves, and thus assures saturated brine at all times. It should also be obvious that since the very purpose of using salt on fish is to extract water the addition of water at the beginning simply supplies just so much water to the salt and satisfies the affinity of salt for water to that extent. The water should come from the fish and not elsewhere.

To put into words the conclusions from this section of the paper, when salt is applied dry to the fish there is a more rapid penetration of salt, less decomposition of fish, and it is possible to preserve fish