REFRIGERATION AND FREEZING OF FISH 



329 



duction of frozen fishery products by geographical sections is also presented. 

 Cold storage holdings of fish and fishery products are given in Table 87. Most 

 of the frozen fish and fishery products are held in the New England, Middle 

 Atlantic, and Northern Pacific coastal states, and in the Great Lakes region. 



1940 1941 1942 1943 1944 1945 1946 1947 1948 



(Courtesy U. S. Fish and Wildlife Service) 



Fig. 16-1. During 1948, stocks of frozen fish averaged slightly more than 

 in 1947. In the early part of the year they were somewhat lower than in 1947, 

 but large holdings in the latter part of the year raised the average above the 

 1947 level. A peak of 158 million pounds was reached on December 1— only 

 slightly lower than the record holdings of November 1, 1946. 



Production of frozen fish set a new record of 291,987,979 pounds— an in- 

 crease of 18 per cent from the previous year. The largest gains recorded 

 among major species were in the production of rosefish fillets, whiting of all 

 kinds, and halibut. Freezings of mackerel registered a sharp decline in 1948. 

 It is estimated that a catch of approximately 625 million pounds of fish and 

 shellfish was required to produce the nearly 292 million pounds of round, 

 dressed, and drawn fish, fish fillets, and packaged shellfish frozen during 1948. 



The Nature of the Preservation of Fish by Freezing 



Fish are generally recognized as being highly perishable. Shortly after they 

 are caught, certain changes begin to take place, at first not undesirable, but 

 which, if permitted to continue, rapidly destroy the suitability of the fish for 

 human consumption. One of the earliest changes is the coagulation of the cell 

 proteins which causes a general body rigidity or stiffness, known as rigor mortis. 

 This condition comes about sooner and lasts a shorter time at higher temperatures 

 than at lower temperatures. Rigor mortis is a characteristic of perfectly fresh fish. 

 After it passes away, various other changes occur, some of an external character 

 which serve as an index to the quality of the fish and others of a chemical nature 

 which affect the quality of the flesh. These changes are principally as follows: 



Autolysis. The tissues of fish, like those of other animals, contain enzymes which 



