24 



COMERGIAL FISHERIES EEVTEM 



Vol. IS, No, 4 



would be considered of inferior grade. It has been found tliat when salmon are frozen, 

 thawed, and canned, the amount of free oil is lower than in cases where the fish have 

 not been frozen. Some free oil is always present, but there is a definite decrease 

 in the amount. This lowers the value of the pack in the eyes of certain brokers, 

 especially in the case of the more oily and expensive species, such as canned Chi- 

 nook salmon. The nutritive value of the fish has not been diminished because the 

 total oil content of the canned salmon remains the same. It is merely that more of 

 the oil is held within the tissue of the fish canned from frozen salmon than is the 

 case of fish which had never been frozen. 



In addition to these changes resulting in loss of free oil and excessive curd 

 in salmon canned from frozen fish a definite change in the texture of the fish is 

 noticeable. Salmon canned from frozen fish tends to be firmer and appears drier 

 than that canned from fresh (unfrozen) fish. Many individuals do not find this ob- 

 jectionable when it is present to a slight extent and some even prefer it to the 

 softer, moist texture of a normal pack. In many instances, however, the texture 

 becomes excessively firm and even tough. The salmon seems much drier and has a 

 definite "woody" texture noticeable when eaten. This is especially true of packs 

 prepared from salmon frozen and stored for periods longer than two months and it 

 is objectionable to most people. Apparently these alterations in the texture of 

 the fish are related to the changes which cause loss of free oil and presence of 

 excessive curd in salmon canned from frozen fish. 



These changes resulting in loss of free oil, formation of curd, and develop- 

 ment of undesirable texture in salmon canned from frozen fish are changes forwhich 

 there is no simple remedy as yet. However, neither the curd nor free-oil problem 

 is extremely detrimental but does cause a slight lowering in the quality of the fish. 



Table 1 



Summary of Importance of Various Problems in 

 Canning Different Species of Frozen Salmon 



Problem 



SpoilageV . 



Oxidation^/ 



Curd2/ 



Free oil2/ 



Abnormal textured' , 



Chum 



xxxxx 



XXX 



XXX 



X 



XXX 



Relative Importance 



Pink 



XX3CXX 



xxxxx 



XXX 



XX 



XXX 



Silver 



xxxxx 



XXX 

 XXX 

 XXX 

 XXX 



Sockeye 



xxxxx 



XXX 



xxxx 

 xxxx 



XXX 



King or 

 Chinook 



xxxxx 



XXX 



xxxx 

 xxxx 



XXX 



Table 1 sum- 

 marizes the relative 

 iii5)ortance of the 

 problems of spoilage , 

 oxidation, curd, and 

 free oil when dif- 

 ferent species of 

 salmon are canned 

 from frozen fish. 

 Spoilage of the fish 

 before they are com- 

 pletely frozen can 

 be a very serious 

 problemwith any of 

 the five species. 

 The least difficulty 

 is encountered with 

 the other problems 

 when frozen chum 

 salmon is canned. 

 Frozen pink salmon 

 can be successfully 

 canned provided ade- 

 quate care is taken to proteat it against oxidation in cold storage. With silver, 

 sockeye, and king salmon, even with the best freezing and storage handling methods, 

 some small though definite decrease in quality of the canned salmon will result. 



Vthis problem can easily be overcome by use of proper techniques in 

 freezing the fish. 



2/THIS problem can be greatly REDUCED OR ELIMINATED IF ADEQUATE 



TECHNIQUES ARE APPLIED IN STORING THE FROZEN FISH AND IF IT I S NOT 

 ATTEMPTED TO STORE THE FISH FOR TOO LONG A PERIOD OF TIME. 



3/THESE PROBLEMS CANNOT BE COMPLETELY CONTROLLED BY PROPER FREEZING 

 AND STORAGE TECHNIQUES, BUT CAN BE HELD TO A MINIMUM BY NOT STOR- 

 ING THE FROZEN FISH FOR TOO EXTENSIVE A PERIOD OF TIME. 



XXXXX FACTOR OF CONSIDERABLE IMPORTANCE. 



XXXX FACTOR OF IMPORTANCE. 



XXX FACTOR OF SMALL IMPORTANCE. 



XX FACTOR OF VERY SMALL IMPORTANCE. 



X FACTOR OF NEGLIGIBLE IMPORTANCE. 



