A COMPARATIVE STUDY ON FATTY ACID COMPOSITION OF SHELLFISH
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A difference between compositions of the fatty acids has been discussed in another paper in this issue dealing with the meat of two kinds of shellfish, gastropoda and pelecypoda. It is inferable that non-depot lipids of fish flesh might have their own specific composition pat-terns of fatty acids according to their living environments or food habits. Thirty-six kinds of materials including shark, bony fish, and their processed products, were purchased from the market to study the patterns. Lipids were extracted from dorsal muscle which usually contains depot lipids less in amount than the flesh of other parts. Total cholesterol and fatty acid composition were examined in the same manner as described for shellfish. The following are the results from the data shown in Tables 1 and 2. 1) In the dorsal flesh cholesterol content varied from 9.5mg of flying fish to 72mg of pond smelt; though the majority of sea fish had it in the range of 40±10mg, rainbow trout, loach, and pond smelt showed it with slightly higher value of 70-72mg. 2) Lipids of dorsal flesh showed less contents of such fatty acids as C14 saturated, C16:1, C18:1, and C20:1, and more quantity of C22:6, than the lipids of ventral flesh. 3) A pattern of fatty acid composition shown in Table 3 was obtained by averaging the results from seventeen marine bony fish and three cured products which had less than 1% of oil contents in the dorsal flesh and more than 15% of C22:6 fatty acid in the lipids. 4) In case of inshore bottom fish, C22:6 acid was found around one tenth of total acids. Two species of shark had a resemblance in fatty acid composition between them (Fig. 4), but those were different from the pattern of Table 3. 5) Fresh water fish, such as loach and sweet smelt, contained 1.3-2.5% of C22:6 acid with a distinct amount of C18:3 acid which was scarcely present in sea fish (Figs. 1 and 2). In the meat of rainbow trout and pond smelt, however, C22:6 acid reached to 14.9-28.9%, almost similar in amount to the acid found in marine fish (Fig. 3).