REFRIGERATION OF FISH 583 



6. The amount and rate of penetration of salt into the tissues of fish varies 

 with the species. In weakfish and flounders the greater part of the salt which 

 can be found in the superficial tissues at the end of a two-hour immersion in 

 brine entered during the first 30 minutes. The absorption in the case of 

 whiting and herring was more gradual, continuing rather uniformly during the 

 two hours. 



7. Inequalities in the far content of the subcutaneous and body tissue of the 

 ash are responsible in large measure for the difference in the susceptibility to 

 salt penetration possessed by fish of the same species and by those of different 

 species. 



Stiles 47 gives several tables of analytical data, of which one is 

 reproduced here as Table 23, showing the influence of the length of 

 time of immersion on penetration of salt in different parts of pike. 



Table 23. — Influence of time of immersion on penetration of salt 



Region of fish 



Near body cavity 



Muscle tissue just under the skin. 

 By the wall of the body cavity... 



Salt in fish after 

 immersion in 21 

 per cent solution 

 at 2.3° F. 



5 minutes 1 hou 



Per cent 



0.17 



.22 



2.51 



Per cent 



0.76 



.29 



3.51 



When the fish are just removed from the brine any excess of salt 

 will be in the skin and immediately underlying tissues. In time 

 this salt seems to diffuse slowly throughout the fish and in this way 

 becomes unnoticeable. Almy and Field observed that salt will even 

 penetrate a block of ice and diffuse toward its center when the block 

 is immersed for two hours in brine, even though the brine is at its 

 freezing point. 



Practical importance of salt penetration. — Salt, being a harmless 

 substance, is of practical importance only insofar as, in penetrating, 

 it (a) salts the fish excessively for taste, or (b) prevents glazing. 

 It is not observed by any of the investigators that any fish have been 

 too salty for taste except where flounders (a thin fish w r ith large 

 surface) w T ere frozen in brine far too strong and too warm. Pre- 

 vention of glazing, however, is of more consequence. It has been 

 discovered independently by two or three investigators (including the 

 present writer) that brine-frozen fish, if the penetration of salt is 

 held to small proportions, can be glazed by washing the brine from 

 the surface before the glaze is applied. 4 * 



Th : s washing may be done either by moving the fish under fresh 

 water or by spraying the suspended fish with fresh water. 49 It was 

 found possible satisfactorily to glaze fish that had been frozen in 

 brine without crystallization of ice. The Booth Fisheries Co. in 

 Seattle, Wash., glazed smelt after freezing them in brine, washing 

 them off, placing them in a cold room for awhile, then applying the 



47 " The preservation of food bv freezing, with special reference to fish and meat," by 

 Walter Stiles. Department of Scientific and Industrial Research, Food Investigation 

 Board, Special Report No. 7, 186 pp. London, 1922. 



48 See " Refrigeration in the fish trade," by W. E. Warner. Cold storage and Produce 

 Review, Vol. XXX, 1917, pp. 105-114. London. 



49 H. F. Taylor, U. S. Patent 1468050, Sept. 18, 1923. 



