COMPOSITION OF FISH 343 



gory A while other species of category B may occasionally fall in cate- 

 gory C. The latter category, in fact, contains few species which contain 

 enough oil (over 15 per cent) to fall predominately in this category, and 

 most of the species which are of type C are those which more usually 

 fall in category B but at certain seasons of the year are of type C. Table 

 26.4 lists fish by categories, and where a species may fall into more than 

 one category, the primary categories are shown. 



Proximate Composition of Parts of Fish 



The proximate composition of the edible flesh (skin-less, bone-less fil- 

 lets) varies from one part to another. There is a tendency for segments 

 near the head of a fish to have a higher oil content than those near the 

 tail, and this difference may be quite pronounced. Thus in salmon there 

 may be nearly twice as much oil in a slice near the head as in a slice 

 from the same fish near the tail (see Table 26.5). 



Table 26.5. Proximate Composition of Slices of a 



Pink Salmon {Oncorhynchus gorbuscha) Taken at 



3 Positions 



Location of Slice Moisture Protein Oil Ash 



Fish contain two types of muscle, the light which predominates and 

 the dark flesh which occurs usually in small areas, such as beneath the 

 skin at the lateral line. There is a difference in composition between these 

 two types of muscle, with the dark flesh generally having a higher oil 

 content and a lower protein content. Sometimes this difference, particu- 

 larly that in the oil content, may be considerable (see Table 26.6). 



Table 26.6. Proximate Composition of Light and Dark 



Tissue of Edible Flesh of Pink Salmon 



{Oncorhynchus gorbuscha) 



Type of Tissue Moisture Protein Oil Ash 



% % % % 



Light 77.4 20.4 2.1 1.25 



Dark 69.9 17.5 12.5 1.20 



The trimmings of fish (all of the fish except the edible flesh) usually 

 have a considerably higher oil and ash content and lower protein content 



