SOME PROBLEMS OF THE FISHERIES 755 



Fish-Freezing Problems 



The production of frozen packaged fish has made great advances, and a good 

 quality product is now available in most cities of the United States. There remain, 

 however, many problems in connection with this industry which need to be 

 solved. Some of the most difficult pertain to production. In general, fishing takes 

 place in temperate areas, that is, in areas where the temperature of the water sel- 

 dom rises above 50° F (10° C). In order to accommodate themselves to their 

 surroundings fish maintain body temperatures that are seldom more than 1 or 2 

 degrees above the surrounding water temperature. When they are caught and 

 landed on the deck of the vessel in an air temperature of 60 to 80° F { 15.6 to 

 26.7° C), autolytic deterioration is greatly increased. It is doubled or tripled, 

 depending upon the air temperature and the length of time required before the 

 fish can be stored in crushed ice in the hold of the vessel. 



In many instances a week to 10 days lapse between the time of capture and the 

 landing of the catch at points of production where the fish can be prepared for 

 packaging and freezing. Even though fish remain packed in ice throughout this 

 period, autolysis continues at a reduced rate. As a result, fresh landed fish are 

 often of inferior quality. 



Freezing fish on board the tuna clippers has been common practice for a num- 

 ber of years. It is estimated that these vessels equipped to freeze fish at sea cost 

 between $300,000 and $500,000. All tuna frozen in this manner go to the can- 

 neries. However, several vessel operators are investigating the possibility of im- 

 proving the quality of other fish by freezing at sea. Several vessels, equipped for 

 the preparation of frozen packaged fish, are now in operation. However, many 

 of the operational problems involved in this instance remain to be solved in a 

 satisfactory maimer. 



The characteristics of the flesh of fish introduce some additional problems in 

 handling. The fat content varies considerably with different species, and within 

 the species, depending upon the season of the year. It is one of the most easily 

 oxidized of all fatty substances, and even at temperatures considerably below 

 0° F (— 17.8° C) it becomes rancid and imparts unpleasant flavors and odors 

 to fishery products. As far as present knowledge indicates, there is no way to 

 prevent limited oxidation in all species, even those with relatively low fat con- 

 tent. Only moderately successful attempts have been made to eliminate this 

 difficulty. Even storage in an almost complete vacuum is not entirely satisfactory. 

 The theory has been advanced that there is a chemical rearrangement of the 

 components making up the fat, particularly when it is in contact wdth protein. 



Enzymatic action of the fish flesh also causes deterioration in cold storage. It 

 has been proven that the gradual breakdown of the tissue of the flesh continues 

 even when the fish are frozen and stored at low temperatures. Shellfish are more 

 susceptible to this type of breakdown than any other fish. In some of the labora- 

 tory tests carried out by the Fish and Wildlife Service it has been shown that 

 deterioration takes place in fish even in sealed glass jars, which entirely exclude 

 the air. 



Although ways to stop enzymatic action in frozen fish have been given some 

 attention, the problem is far from being solved. Consideration is being given to 

 the treatment of fish with some of the numerous anti-oxidants to prevent ran- 



