fillet yield), the proximate chemical 

 composition (moisture, protein, fat, 

 and ash), and the sodium and potassium 

 content of fish as they vary between 

 species with season of the year, and 

 with different geographical areas. Re- 

 sults of studies show that fish have a 

 low sodium content, and the methods 

 by which fish are cooked have a pro- 

 found influence on the final sodium con- 

 tent of the fish as they are eaten. Of 

 all the common cooking methods tested, 

 boiling is the most efficient in lowering 

 the sodium content; steaming, broiling, 

 and baking are next in order of im- 

 portance. These findings have great 

 significance to people whose physical 

 condition requires a low sodium diet. 

 These tests also confirm the fact that 

 the practice of brine-dipping fillets 

 destined for the frozen market results 

 in an increase in the sodium content 

 of the fillets, thus precluding their use 

 in sodium-restricted diets. By taking 

 advantage of these findings, industry 

 can insure the retention of hospital 

 kitchens as outlets for its frozen fish. 



Flavor and Odor Components. 



Research on flavor and odor has as 

 its goal the detection, identification and 

 separation of those compounds respon- 

 sible for the undesirable odor and 

 flavor changes that occur in fishery 

 products during frozen storage. In- 

 formation obtained will be used in 

 establishing methods to minimize any 

 undesirable changes, thereby enabling 

 frozen fish to retain that fresh-from- 

 the-sea flavor. 



Results during the past year indicate 

 that chemical methods can be used to 

 detect the quantitative differences in 

 the carbonyl content of fresh and frozen 

 haddock and to relate this to storage 

 age and quality. This work is progress- 

 ing satisfactorily, and it is expected 

 that as a corollary to this study a 

 chemical test will be developed that 

 will distinguish recently frozen fish 

 from frozen-stored fish. 



Protein Studies. 



Fundamental changes in the order of 

 arrangement of the molecules compris- 

 ing the protein of the muscle of frozen- 



Figure 11. — Determining the spectra of compounds that 

 contribute to the odor and flavor of fish. 



stored fish contribute to toughness and 

 loss of quality. Solution of this prob- 

 lem will be an important contribution 

 in increasing the acceptability of and 

 the demand for frozen fish products. 

 Research at this laboratory is aimed 

 at identifying the chemical groups that 

 are directly involved in bringing about 

 these changes in protein. The hypoth- 

 eses are that: (1) the increased tough- 

 ness of frozen- stored fish is due to 

 polymerization and is occurring through 

 the formation of new disulfide linkages, 

 and (2) the apparent dryness in the 

 muscle of frozen- stored fish is due to 

 a loss of function of certain molecular 

 groups which, in fresh muscle, are 

 free to bind large quantities of water 

 and give to the flesh the attribute of 

 succulence. 



The first hypothesis is being tested 

 by measuring the rate of changes of the 

 shape and weight of the protein mole- 

 cules in the presence and absence of 

 p-chloromercuribenzoic acid. This 

 reagent is specific for sulfhydryl 

 groups in that it attaches itself to them 

 alone. By so doing, it prevents sulf- 

 hydryl groups from participating in 

 reactions and therefore, should main- 

 tain the protein molecules in a mono- 

 meric state during storage. Measure- 

 ments of changes in molecular shape 



