84 THE SALTING OF FISH. 



These results concerning the rate of formation of amino-acid 

 nitrogen check with those on the penetration of chlorides; that is, 

 where there was a slowing up in the rate of penetration of chlorides, 

 there is an increase in the rate of amino-acid formation. The 

 changes are approximately the same, except in the case of the effect 

 of the sulphates. The results obtained from the work on rate of 

 penetration of salt adulterated with sodium sulphate show a marked 

 decrease in the rate of penetration, due to the impurity. The in- 

 crease in rate of production of amino acids clue to the presence of this 

 impurity is very slight. However, the work on the rate of penetra- 

 tion was done with salts containing 10 per cent of sodium sulphate. 

 It may be that this marked retardation takes place only at high con- 

 centrations of sodium sulphate, when there is a marked hardening 

 of the tissues. 



DISCUSSION". 



PHYSICAL EFFECTS ON FISH. 



This work on the preservative action of different salts was done on 

 alewives, whereas the penetration of salts were followed in sque- 

 teagues. The hardening and whitening action of calcium and mag- 

 nesium salts was marked on alewives ; but it was less noticeable than 

 in the case of squeteagues. Five per cent of sodium sulphate had 

 practically no whitening action on alewives and very little hardening 

 action. It may be that 10 per cent of sodium sulphate in salt is 

 required to bring out the whitening power. No lot of alewives was 

 salted with salt containing more than 5 per cent of sodium sulphate. 



A POSSIBLE EXPLANATION OF RESULTS. 



The writer believes that the hardening action of calcium and mag- 

 nesium salts on the tissues of the fish is responsible for the retardation 

 of the penetration of the chlorides. This, in turn, is at least partially 

 responsible for the lesser preservative action of the impure salts. 

 Sodium sulphate evidently acts only when in greater concentrations 

 than it is ordinarily found in commercial salts. Its deleterious action 

 as an impurity is, therefore, not to be feared. 



PRACTICAL APPLICATION. 



When fish are salted at any temperature averaging below 50° F., 

 salts may be chosen that will produce the desired quality of salted 

 fish. When a hard, white fish is desired, salts high in calcium and 

 magnesium salts may wisely be chosen. However, if a soft, pliable 

 fish is desired, pure salts should be used. 



When the average temperature of salting is above 50° F., greater 

 care should be used in the selection of salt. This becomes of par- 

 ticular importance when the fish are salted, either round or contain- 

 ing blood, roe, or milt, as these fish are much more likely to spoil than 

 when they are thoroughly cleaned. In this case the smaller the 

 amounts of calcium and magnesium salts present the more desirable 

 the salt. Fish salters working in warm climates should strive to 

 obtain salt containing less than 1 per cent of total calcium and mag- 

 nesium salts. . Sulphates are never present in large enough quanti- 

 ties to lower the effectiveness of the salt as a preservative. 



