THE RESIDUAL LIPIDS 

 OF FISH PROTEIN CONCENTRATES 



Previous papers (Medwadowski, Van der Veen, 

 andOIcott, 1967, 1968; Medwadowskietal., 1971), 

 presented data on the residual lipids in fish pro- 

 tein concentrates (FPCs) from red hake, Uro- 

 phycis chuss; Gulf menhaden, Breuoortia pa- 

 tronus; pout, Macrozoarces americanus; and 

 alewife, Alosa pseudoharengus; and some pre- 

 liminary data on the effects of storage on the 

 lipids. After 6 mo at 37° or SOT, there were 

 decreases in the contents of highly unsaturated 

 fatty acids (C20:5 for alewife and C20:5 and 

 C22:6 for pout and Gulf menhaden), and an 

 appreciable decrease in the amount of lipid 

 extractable from a menhaden FPC that origi- 

 nally contained 0.56% lipid, but no change in 

 the amount extractable from FPCs that origi- 

 nally contained 0.11% (pout) or 0.06% (alewife) 

 lipids. 



In this paper we present data on the composi- 

 tion of lipids extracted from additional samples of 

 FPCs (from Pacific hake, Merluccius productus; 

 northern anchovy, Engraulis mordax; Atlantic 

 menhaden, Brevoortia tyrannus; and Atlantic 

 herring, Clupea harengus harengus) and also on 

 the effects of storage, at several temperatures 

 and humidities, on the composition of the residual 

 lipids in a hake FPC preparation. 



Materials and Methods 



The FPCs had been prepared at National 

 Marine Fisheries Service laboratories by counter- 

 current extraction of ground fish with hot iso- 

 propyl alcohol, followed by solvent removal and 

 milling (Knobl et al., 1971). 



Samples of a hake FPC were stored at the 

 College Park Fishery Products Technology Labo- 

 ratory at 21. r, 32.3°, and 43.3°C and at 50% 

 and 90% relative humidities for each temperature 

 for periods of 1, 3, 6, and 12 mo (Green, 1972). 

 The control was held at -29°C and ambient 

 freezer humidity. The samples were shipped in 

 plastic bags, cooled with dry ice (except for the zero 

 time control sample which was shipped at ambient 

 temperature), and stored at -18°C pending 

 analyses. 



Two procedures for determining moisture 

 content (volatile matter) of the hake FPC samples 

 were compared: 30-45 h at 110°-115°C, and 1 h 

 at 130°C (Association of Official Analytical 

 Chemists method, Horwitz, 1970:211). In the 



latter case, the drying was interrupted after 30 

 min; the caked meal was broken with a stirring 

 rod; and the meal adhering to the rod was brushed 

 back into the glass-stoppered weighing bottle in 

 which the sample was being dried and weighed. 

 Results from the two methods were in close agree- 

 ment. The shorter method with the modification 

 of the intermittent stirring was used thereafter. 

 The lipids were extracted (Soxhlet) in duplicate 

 or triplicate with chloroform-methanol (2:1) from 

 200-g portions of the FPCs in large prewashed 

 thimbles and analyzed as described by Medwadow- 

 ski et al. (1971) with the following modifications 

 in some cases. Purification was accomplished with 

 a 2 X 22 cm Sephadex^ column chromatography 

 (Siakotas and Rouser, 1965; Rouser, Kritchevsky, 

 and Yamamoto, 1967) and flow was by gravity. 

 The saponification-methylation procedure used 

 for determination of fatty acids was that described 

 by Metcalfe, Schmitz, and Pelka (1966). The 

 amounts of lipid were determined by drying 

 aliquots of their solutions on a warm hot plate 

 in preweighed disposable aluminum pans (Rouser 

 et al., 1967). 



Results and Discussion 



Yields and fatty acid composition of the lipids 

 extracted from seven separate runs — three from 

 Pacific hake, two from northern anchovy, and one 

 each from Atlantic herring and Atlantic men- 

 haden — are shown in Table 1. 



The two anchovy FPCs had somewhat similar 

 fatty acid compositions; the main differences were 

 in the amounts of C16:0 and C20:5. Herring FPC 

 contained relatively larger percentages of C20:l 

 and C22:l. The Pacific hake FPCs, samples 8, 

 9, and 10, were similar in fatty acid composition 

 but contained relatively more C18:1 than the 

 FPCs from the other fish. The lipids of samples 

 8, 9, and 10, in general, resembled those of a 

 red hake FPC, P-5 (reported previously by 

 Medwadowski et al., 1967), and those of fresh 

 red hake (Medwadowski et al., 1967, 1968). The 

 Pacific hake FPCs, samples 8. 9, 10, and 78-103 

 (Table 3), contained higher percentages of C20:5 

 and C22:6 than red hake FPC P-5 and fresh 

 red hake. Possibly less oxidation had occurred 

 during processing, or the fish from which the FPCs 

 were made had been subsisting on different 

 foodstuffs. 



'Reference to trade names does not imply endorsement by 

 the National Marine Fisheries Service, NOAA. 



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