14 



U. S. BUREAU OF FISHERIES. 



open, scraped, and washed before the salt is applied. By what cri- 

 teria can we judge the merits of these various methods? The best 

 way to answer this question is : Other conditions being held con- 

 stant, which method or methods of cleaning result in least decom- 

 position during the salting process? 



A series of trials was made by cleaning the fish by the various 

 methods and salting them by the same process and determining the 

 amounts of amino acid nitrogen developed. Two sets complete were 

 tried, one consisting of one sample each cleaned by the various 

 methods and held at a temperature of 79° F, during the salting 

 process; another set similar to the preceding but held at 88° F. 

 during the salting process. Both temperatures are high for salting 

 fish, and the test is correspondingly severe. The results are shown 

 in the following table, which is abbreviated from the paper by 

 Tressler : 



Development of Amino Acid Nitrogen in Fish Cleaned in Various Ways. 



[Fish salted four hours after capture, with Diamond Flake salt containing 99.78 percent sodium chloride; 



salting period, nine days.] 



Method of cleaning. 



Condition of fish at 

 end of period. 



No cleaning, salted round 



Pipped 



Head cut off, abdominal cavity spUt open, viscera, except 

 milt and roe, removed. 



Cleaned perfectly, milt and roe removed, kidney and mem- 

 branes scraped, and all blood washed out. 



No cleaning, salted romid 



Pipped 



Head cut off, abdominal cavity spUt open, viscera, except 

 milt and roe, removed. 



Cleaned perfectly, milt and roe removed, kidney and mem- 

 branes scraped, and all blood washed out. 



Badly spoiled, bloated. 

 Spoiled. 

 Do. 



Excellent condition. 



Badly spoiled, bloated. 

 Badly spoiled. 



Excellent condition. 



Since amino acid nitrogen indicates decomposition, the conclu- 

 sions from this table are entirely obvious. Only those fish were 

 successfully salted at temperatures of 79 and 88° F. which had been 

 thoroughly cleaned and from which all blood had been removed. 

 AVhile these high temperatures were chosen for the test because severe 

 tests bring out differences in a more striking way, the differences will 

 still exist even at lower temperatures and manifest themselves in the 

 poorer or better quality of product. Now, it may be either the blood 

 or flesh, or both, in which the decomposition takes place. Since the 

 perfectly clean fish decompose only slightly, it may be that only the 

 blood decomposed in such cases as those given in the table, and that 

 the decomposed blood pervading the otherwise sound tissue gave the 

 appearance and odor of decomposition to the whole fish. On the 

 other hand, it is possible that the enzymes in the blood when present 

 operate to decompose not only the blood proteins but the tissue pro- 

 teins also. However, this may be, the indisputable fact remains 

 that if fish are to be salted in very Avarm weather it is absolutely 



