Date of Award

1994

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Nutrition and Food Sciences

First Advisor

Spiros M. Constantinids

Abstract

Shark-fins are one of the most expensive fish products in the world that fetch high prices in the oriental market. The value of the fins depends on the species, size and quantity of fin needles. These factors are largely determined by the intrinsic chemical and physical characteristics of the shark-fins which this study addressed.

In order to formulate the relationship between body size and fin sizes of sharks, seven hundered and sixty-six shark specimens were measured and recorded from landing sites in Oman between July, 1991 to June 1992. The regression of body size in relation to the fin sizes revealed different R2 within and among the different species of sharks. The best correlation was between the precaudal length and all four fins (dorsal, pectoral, tail and lower lobe of tail), especially in the spinner shark (R2=0.97). This will aid shark-fin vendors and purchasers to estimate sizes of the identified species to predict their values in the market.

In the yield studies, the white fins gave a higher yield than the black fins. However, the lower lobe of tail from black varieties gave the highest yield in fin needles, especially in the silky shark. Processing and extraction of fin needles from pectoral fins of dogfish was more economical than from the tail as it required a about half the time of the tail processing.

The thickness of fin needles was directly proportional to the size of the fins. Due to swelling in preheated water at 60-7o0 c, fin needles increased in thickness to an average of 79.8% of their original width and decreased in length to an average of 57% of their original length.

The proximate analysis of fin needles showed a very high nitrogen content, very low ash and no oil content. ' non-protein nitrogen was not detected. To the contrary, the fin's flesh had a higher content of non-protein nitrogen, ash and fat than the fin needles. The amino acid distribution of elastoidin is similar to that of collagen, except that the former contains cystine and a higher amount of tyrosine. The amino acid profiles indicate no significant difference between fin needles extracted from white varieties or black varieties of fins. The essential amino acids score of elastodin was less than half that of casein. Thus shark-fin is of low nutritional value. Elastoidins are very rich in sulfur which may explain the peculiar hydrothermal properties that distinguish them from other collagens.

Needles extracted from shark-fins are of high commercial value and are in high demand among the Chinese. This suggests that future studies could concentrate in finding innovative methods to produce artificial needles or use the extrusion techniques to prepare protein fibers from shark-fins simulating the shark-fin needles.

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