10 



U. S. BUREAU OF FISHERIES. 



It is seen that the brine-salted fish consistently underjjo 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: 



Penetration of Salt. 



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 con- 

 centrations 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. Stir- 

 ring 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 dif- 

 ferences 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 



