NUTRITIVE VALUE AND QUALITY OF FISH 365 



are frequently delicate, perhaps quite faint, and certainly only transitory. 

 By stage 2, much if not all of the natural species characteristic odors and 

 flavors have disappeared. Unfortunately, the largest part of the fish con- 

 sumed has reached or passed stage 2 so that the pleasing natural flavors 

 and odors are often absent. 



At stage 3, a group of perhaps quite unrelated odors and flavors, which 

 are referred to as ''fishy,"'' begin to accumulate. At this stage these odors 

 and flavors may be so faint as to be quite vague, almost indescribable. 

 During stage 4, these odors often develop to a quite definite, character- 

 istically sweet type if the fish is well refrigerated; yet, the odor is still 

 not considered in any way objectionable. At stage 5, various amine and 

 other odors and flavors have given the fish definitely undesirable proper- 

 ties which, while perhaps not rendering it entirely inedible, have certainly 

 drastically lowered its quality. At stage 6, where sulfide and other ob- 

 noxious odors and flavors predominate, the quality of the fish has sunk 

 to such a low level that by most standards it is considered to be quite 

 inedible. 



Another type of odor and flavor which results from oxidation and ran- 

 cidification of the lipids of fish is more important with certain preserved 

 (especially frozen) fish than with the iced fish product. These rancid 

 flavors and odors of fish oils range from a bland, almost tasteless form in 

 the fresh oil through various vague ''fishy" stages to a fairly typical 

 rancid flavor having a sharp, sometimes acrid taste and possessing a 

 strong after-taste. 



As has been noted by Stansby'^, the odors and flavors associated with 

 bacterial decomposition, primarily of the nitrogenous components of fish, 

 are not necessarily distinct and separate from those associated with fish 

 oil oxidation. On the other hand, it has been shown^-^ that nitrogenous 

 components may combine in some fashion with lipid and during oxi- 

 dation develop certain characteristically "fishy" odors in oils. On the 

 other hand, fish spoiling primarily in a bacteriological pattern may con- 

 tain carbonyl or other such compounds which may have arisen from the 

 fish oil. 



Texture. Normal fish texture may vary over a fairly wide range and 

 still be considered to be entirely acceptable, depending upon the particu- 

 lar product. Thus halibut is normally of a flaky, moist texture wherein 

 presence of stringiness would be considered abnormal; yet, halibut cheeks 

 are prized by the connoisseur for just such a stringy texture. For most fish 

 the texture characteristics considered normal and desirable include moist- 

 ness, flakiness, and absence of toughness. The typically desirable fish 

 from a texture standpoint when chewed has a moist feel in the mouth, 

 but, as pressure is applied in chewing, there is not an excessive pressing 



