April 1951 



COM^'ERCIAL FISHERIES RSVEW 



21 



Stored under different conditions and the resulting packs compared for quality 

 against fish canned from samples which had not been frozen. Relatively large sam- 

 ples, consisting of a considerable number of cases, have been packed and examined. 

 Tests on these packs are still continuing but a number of general conclusions have 

 been drawn so far. These will be discussed without specific reference to any 

 scientific data which will be published at a later date after the tests have been 

 completed. 



There are three types of changes vrtiich may take place when using frozen salmon 

 for canning that do not ordinarily occur when fresh (unfrozen) fish are canned. The 

 first change involves bacterial spoilage of the fish during the freezing process; 

 the second, deterioration, including oxidation of the fish after it is frozen and 

 while it is being held in the frozen state in cold storage; and the third, altera- 

 tions in the salmon which are brought about directly by the freezing process. The 

 first two of these involve changes which can be eliminated or greatly minimized by 

 proper handling techniques; the third, which is beyond control by proper handling 

 techniques, can be held to a minimum by limiting the storage period of the frozen 

 fish. 



BACTERIAL SPOILAGE OF SALMON DURING FREEZING 



Undoubtedly, the 

 most serious and yet the 

 most easily prevented 

 change which may take 

 place in frozen salmon 

 is bacterial spoilage 

 diiring the freezing 

 process. This takes 

 place when the fish are 

 frozen at an exceedingly 

 slow rate — many hours 

 elapse before the fish 

 are frozen completely 

 through to the center. 

 This difficulty is en- 

 countered when inade- 

 quate freezing facili- 

 ties are available and 

 a larger quantity of 

 fish frozen than the 

 refrigeration capacity 

 of the freezing equip- 

 ment is designed to 

 handle. Such a situ- 

 ation often occurs on 

 vessels where space is at a premium and it is impossible to carry a large reserve 

 of refrigeration. In the case of refrigerated tuna boats, fish are usually frozen 

 in brine wells and it is easy to place more fish in the well than the system was 

 designed to handle. Poor circulation of the brine may cause extremely slow freezing 

 to take place at certain locations in the brine well. " 



In freezing, even when proper circulation of the brine takes place and no over- 

 crowding of the wells is attempted, the outside of the fish first starts to freeze, 



REMOVING CANS OF SALMON FROM RETORT AFTER PROCESSING AT A 

 SERVICE TECHNOLOGICAL LABORATORY. 



