CHAPTER 14 



Fish and Shellfish as Food 



Chaeacteristics of Fresh Fish: Appearance, Chemical Composition, 



AND Nutritive Value. 



Physical Characteristics 



When a fish dies it stiffens almost immediately, the flesh becoming rather firm 

 and elastic. This condition is called rigor mortis and is a guarantee of perfect 

 freshness. But since, even under the most favorable storage conditions, rigor 

 mortis gradually disappears in a short time, its absence does not indicate that the 

 fish is not suflBciently fresh to be an excellent food. 



The flesh around the large caudal vein and kidney in fresh fish is light colored. 

 As staleness approaches this flesh becomes discolored by the blood. This indicates 

 that the fish has been caught for some time, but does not necessarily mean that 

 it is unfit for food. The presence of this reddish discoloration on the ventral aspect 

 of the backbone should cause the fish to be regarded with suspicion and other 

 tests should be made to discover whether it is stale or putrid. 



Since the personal factor enters largely into the judging of the condition of a 

 fish by its odor and since fresh fish of different species vary considerably in this 

 respect, the use of the sense of smell is invaluable in the examination of fish. 

 Many individuals have difficulty in distinguishing between the odor of fresh fish 

 and that of slightly tainted or stale fish, but few, if any, have trouble in discern- 

 ing a putrid odor. Fresh fish, just taken from the water, usually have only a mild 

 characteristic fishy odor, somewhat similar to that of seaweed. Fish which have 

 not been eviscerated frequently give off odors suggestive of decomposition long 

 before any spoilage of the flesh has taken place. This is usually caused by a rapid 

 decomposition of the substance upon which the fish have been feeding. 



The gills and the slime give off more pronounced decomposition odors than 

 the flesh, and this may be useful in predicting incipient decomposition. The 

 degree of odor is markedly affected by the temperature. Thus fish which are at 

 32° F (0° C) or below may have only a slight odor which might be increased 

 to a relatively stale one ff the fish were allowed to warm to 60° F (15.5° C) or 

 above. The odor of fish kept in finely crushed ice ordinarily progresses from fishy, 

 through sweet, stale, and finally putrid. 



It requires considerable care to strip the flesh from the backbone of a strictly 

 fresh fish, and many pieces are left adhering to the bone. When the fish becomes 

 stale, the flesh comes away readily and comparatively cleanly from the bone. 

 This is another test which may be applied to show relative freshness. 



The condition of the kidney is a very important criterion in judging freshness. 

 It is a very diffuse, vascular, and friable organ, and rapidly decomposes, passing 

 through different shades of color, to form a reddish brown jelly like mass in a 



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