12 REPORTS OF THE DEPARTMENT OF COMMERCE. 



PRINCIPLES GOVERNING PRESERVATION OF FISH BY SALTING. 



During the lack of proper laborator}^ facilities the Bureau, with the 

 cooperation of the National Kesoarcli Council, was enabled to carry 

 on at Johns Hopkins University Medical School, Baltimore, Md., 

 an investigation of the problems of preserving fish with salt, and Dr. 

 E. V. McCollum kindly volunteered to supervise the work at that 

 institution. Experiments were conducted later at fishing centers in 

 Virginia, Norih Carolina, and Florida. 



The primary object of the investigation was to devise an improve- 

 ment in the present methods of salting fish and to fmd an acceptable 

 way of saltmg fish at summer temperatures, particularly ni the 

 Southern States, where difficulty in the warm months is encountered. 



Incidentally, the work has added materially to our knowledge of the 

 basic principles governing the salting process. The fish used in the 

 experimental work were squeteague and river herring. The rate 

 of penetration of salt into fish and the decomposition of the protein, 

 as indicated by the amount of amino-acid nitrogen formed, were used 

 as criteria of the efficiency of salting methods. 



Sulphates and also salts of calcium and magnesium, as impurities 

 in common salt, were found to retard the penetration of salt into fish 

 muscle, but to produce a firmer, whiter flesh than pure sodium chlo- 

 ride. By reason of retarded penetration, salt containing these 

 impurities permits fish to spoil at a lower temperature than salt not 

 containing such impurities. Of these deleterious substances, the 

 calcium salts are the only ones present in commercial salt in a large 

 enough quantity to have a marked effect on the quality of the fish. 



The removal of all blood and viscera, including roe and milt, appears 

 to be an important factor in the salting of fish in warm climates. 

 Experiments made indicate that the blood spoils at a temperature at 

 least 25° F. lower than the spoilage temperature of the flesh of fish. 



An investigation of the chemical changes taking place in the fat 

 and protein of fish during storage is in progress, and a report of the 

 completed work is being prepared for publication. 



DEVELOPMENT OF A PROCESS FOR RECOVERY OF WASTE BRINE. 



It has been the usual practice among fish curers to discard the 

 used brine employed in brine-salting fish, and also to some extent 

 in the dry-salt process, and to make new brine for new lots of fish. 

 Much salt Jias been wasted, the recovery of which was impracticable 

 for a number of reasons. For example, the brine is loaded with a 

 large amount of organic matter, blood, mucus, soluble proteins, 

 methylamines, bacteria, etc., whose removal would be expensive; 

 and, since salt was comparatively cheap and used in large quantities, 

 any recovery process must of necessity produce results at low cost. 



Recent investigations of the Bureau have shown that a better 

 quality of fish may be produced by using higher grades of salt and 

 have indicated the possibility'' that salting could be successfully accom- 

 plished in warmer climates. Without some recovery process the 

 cost of refined salts may be prohibitive. 



For these reasons the Bureau undertook to develop a process of 

 purifying fish brine without expensive evaporation. Advantage 

 was taken of the absorption by exceedingly fine precipitated particles 

 of a tasteless and inert substance of the suspended and dissolved 



