Promoters of fish oils as omega-3 sources can argue that shellfish carry certain diseases and that fish oils made from reduction of whole fish might be unwholesome. Freshwater fish oils have C20 omega-6 fatty acids with totals roughly equal to omega-3 content, and this would be true of fish lipids and oils from most tropical and some semitropical fish. In theory this commercial process, developed by Eckey for lard, tallow, margarine and shortenings, palm oil, etc., could be adapted for fish oils. If the rest of the fish oil can be salvaged, then in principle a small proportion (1-2%) of oil might be recoverable enriched in eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA). Fat-soluble impurities are also enriched along with EPA and DHA if they do not form urea complexes, but if 80% of the fatty acids are readily eliminated then the expense for final cleanup (of the 20%) is much reduced.

Lipid was extracted from fillets of large Newfoundland winter Atlantic herring (Clupea harengus harengus) gillnetted in Placentia Bay. In the period January through March percent lipid fell more sharply in females than in males, but lipid-iodine values declined at approximately the same rates. Lipid-iodine values were noticeably higher (about 20 units, maximum values ca. 160) than for the oils produced from fish seined in adjacent waters and commercially reduced. It is proposed that these particular herring are an isolated stock peculiar to Placentia Bay, but that they show certain aspects of lipid biochemistry that are influenced by the reproductive cycle in common with other herring from the Atlantic and Pacific oceans.

From merely being cod liver oil taken for vitamins A and D, fish oils have moved into the center stage of fatty acids in nutrition. The analytical work starting in 1950 provided the means to recognize the long-chain and truly essential n-3 polyunsaturated fatty acids vital for retinal, neurological and cellular membrane functions in our bodies. The AEskimo@ studies of twenty years ago have also now been followed scientifically for two decades, into our recognizing fish and shellfish as highly desirable food sources of these n-3 fatty acids for cardiovascular benefits. th century, when organic solvents became available and German scientists were able to extract things like cod fish muscle and human brains. The grey pastes that resulted from these two materials were rather similar, since they were dominated by phospholipids with a substantial proportion of highly unsaturated fatty acids, both materials not yet known to science. Fish oils were used as industrial chemicals for a hundred years though they were not understood in detail. Their uses were partly based on paints and linoleum, materials where the fatty acids we now know to be highly unsaturated could crosslink into polymers. Hydrogenation for margarine was possible from about 1900, but the quality and purity of the raw material was dubious. Sulphur compounds, for example, from the amino acids of fish protein left too long before oil production, poisoned the catalysts. At the time whale oil was preferred as it was a purer raw material, and even as late as 30 years ago seal oil commanded a higher price than fish oil in Canada for margarine and shortening manufacture because of quality and ease of manufacture. Today we know that this procedure applied to marine oils was wasting highly unsaturated fatty acids potentially valuable in our diets. In 1952 Bailey, Carter and Swain published Bulletin 89 of the Fisheries Research Board of Canada. By this time common terrestrial fatty acids such as oleic, linoleic and alpha-linolenic had definite structures and could be discussed for foods, but the long-chain, highly unsaturated fatty acids of marine origin were listed under a variety of names (usually related to the species of fish providing the oil that was examined) and an even greater assortment of positions for the ethylenic bonds. Two teams resolved most of the significant issues. E. Klenk, in Germany, published a series of papers in 1958-1962 accurately defining several marine polyunsaturated fatty acids such as all-cis-6,9,12,15-octadecatetraenoic fatty acid (18:4n- 3, now called stearidonic). The rapid implementation of chromatographic technology, especially thin-layer and gas- liquid chromatography, and adequate funding by the Rockefeller Institute, led to a group there publishing an almost complete analysis of the fatty acids of menhaden oil (Farquhar et al., 1959). The conceptual problem in identifications was that everybody tried to relate these through the positions of the ethylenic bonds relative to the carboxyl group. By 1962 H.J. Thomasson had realized the importance of the other end of the chain (Thomasson, 1962) and with this useful addition most of the work of the biochemistry group of the Hormel Institute and elsewhere on 'essential fatty acids' fell into place. Personally I benefitted enormously from publications of these authors because Halifax, Nova Scotia, Canada, was remote from other centres doing research into highly unsaturated animal and marine fatty acids. Standards were scarce and expensive. With the data available I was able to organise almost all polyunsaturated fatty acids of marine organisms into structural groups, thus easily identifying unknown peaks in one analysis on any GLC column. For example separation factors for ethylenic bonds could be generated from the almost any readily available vegetable oil:

Fatty acids (FA) are inextricably linked with key physiological and biochemical processes and are thus integral to proper ecosystem functioning. FA not biosynthesized effectively by animals are termed essential fatty acids (EFA). These EFA are important "drivers" of ecosystem health/stability and are therefore highly conserved in aquatic food chains. Aquatic organisms have been and continue to be our primary source of readily available EFA. However, overfishing and our burgeoning population may be acting in concert to threaten our access to this source of EFA. Here, we review the marine FA synthesis/transport cycle and traditional and nontraditional sources of EFA. Our review suggests that, while some traditional sources of marine oils (e.g., tuna) are in steady decline, other sources (e.g., krill) and technologies (e.g., heterotrophic fermentation) hold great promise for maintaining our access to EFA. We provide a minireview which illustrates that EFA contribute to our health and well-being. Finally, there is growing evidence that EFA have been an important force in our past evolution, leading us and others to speculate that an unbroken link exists between EFA, our present health, and, in all likelihood, our continuing evolution.

The effect of α-tocopherol (αTOH) (50–2000 ppm), γ-tocopherol (γTOH) (100–2000 ppm), and δ-tocopherol (δTOH) (100–2000 ppm) on the formation and decomposition of hydroperoxides in purified fish oil triacylglycerols (TAG) was studied. The tests were conducted at 30°C in the dark. Purified fish oil TAG oxidized very rapidly with no apparent induction period. The relative ability of the tocopherols to retard the formation of hydroperoxides decreased in the order αTOH> γTOH>δTOH at a low level of addition (100 ppm), but a reverse order of activity was found when the initial tocopherol concentration was 1000 ppm. This dependence of relative antioxidant activity on tocopherol concentration was caused by the existence of concentrations for maximal antioxidant activity for αTOH and for γTOH. An inversion of activity, on the basis of hydroperoxide formation, was observed for αTOH at 100 ppm and for γTOH at 500 ppm, whereas the antioxidant activity of δTOH increased with level of addition up to 1500–2000 ppm. None of the tocopherols displayed any prooxidant activity. All three tocopherols strongly retarded the formation of volatile secondary oxidation products in a concentration-dependent manner. At concentrations above about 250 ppm there appeared to be a linear relationship between rate of consumption of αTOH and initial αTOH concentration, in accordance with the linear relationship observed between the initial rate of formation of hydroperoxides and the initial αTOH concentration. The rate of consumption of γTOH also increased with initial concentration, but to a lesser extent than for αTOH. At high levels of addition the rate of consumption of δTOH was independent of initial concentration, appearing to reflect the greater stability of this tocopherol homolog and participation in reactions with lipid peroxyl radicals only.

Menhanden oil was purified by column chromatography to remove minor components. The effect of α-tocopherol (α TOH) (50–500 ppm) on the rate of formation of hydroperoxides in the original menahaden oil and in the purified menhaden triacylglycerol (TAG) fraction was studied at 30°C in the dark. An increase in the initial rate of formation of hydroper-oxides was observed at αTOH concentrations above 100 ppm in both substrates. The original menhaden oil oxidized more rapidly than the purified menhaden, TAG at all antioxidant levels tested, and the presence of minor components in the menhaden oil was found to contribute only to a limited extent to the peroxidizing effect of αTOH. The αTOH did not display any prooxidant activity at either of the concentrations tested when the control oil was the purified menhaden TAG. Addition of ascorbyl palmitate eliminated the initial peroxidizing effect of αTOH, and this emphasizes the participation of the α-toco-pheroxyl radical in the reactions causing an accumulation of hydroperoxides at high concentrations of αTOH.

The emergence of biodiesel fuels as diesel fuel substitutes has led to several studies on their properties. Surface tension, which plays a role in atomization, has lacked attention compared to other properties. This paper presents a method to predict the surface tension of biodiesel fuels based on the fatty acid composition. Several binary, ternary, and quaternary mixtures of fatty acid ethyl ester gas chromatographic (GC) standards were prepared, and we found that a mass-average equation predicted the surface tension of these mixtures within ±3.5% of their measured values. Six complex mixtures of fatty acid methyl ester GC standards that simulated typical oils used as biodiesel fuels were also prepared. For these complex mixtures the predicted surface tensions of the mixtures, calculated from a mass-average equation, were 2–6% higher than the measured values. A mass-average equation was developed in which we used a weighted surface tension for the individual components, and we found that this method predicted the surface tension of the simulated oils within ±4.5% of their measured values. Five natural vegetable oils were used to produce biodiesel fuels by the transesterification process. The predicted surface tensions of these fuels were all within ±3.5% of their measured values. The surface tensions of 15 biodiesel types were then predicted, based on their fatty acid composition as published in the literature. These results show that the differences in surface tension between biodiesel types are not the main cause of the reported differences in engine tests.

Groups of Atlantic salmon parr (mean initial weight 9.5 g) were fed three diets, the first containing no tocopherol supplement, the others supplemented with either all-rac-alpha-tocopherol (A-T) or RRR-gamma-tocopherol (G-T). Tocopherol concentrations in the liver, serum, testes, kidney, brain, gill, muscle, and perivisceral fat were measured after 36 wk. Despite a higher dietary intake of G-T, compared to A-T, deposition of gamma-tocopherol (gammaT) was less efficient than of alpha-tocopherol (alphaT) in most tissues except in the perivisceral fat, an adipose tissue. In fish fed the G-T diet, the gammaT/alphaT ratio was highest in the perivisceral fat and lowest in the liver, indicating that the liver is the most discriminatory organ for retaining alphaT as compared to gammaT, and the perivisceral fat is more suitable for the storage of gammaT. A negative correlation (P < 0.01) was observed between the gammaT/alphaT ratio and the corresponding tissue phospholipid content, suggesting that gammaT is less efficiently deposited compared to alphaT in the phospholipid-rich membranes which are presumed to be the functional site for lipid antioxidants in vivo. During restricted intake of alphaT, the liver and muscle exhibited the greatest reduction of this tocopherol among the tissues analyzed. The presence of minimal alphaT in the muscle from fish fed the tocopherol-unsupplemented diet led to greater susceptibility to lipid peroxidation after frozen storage than was the case for muscle containing higher concentrations of either alphaT or gammaT. However, both alphaT and gammaT were effective stabilizers of salmon muscle lipids during frozen storage.

The purpose of this investigation was to determine whether diets supplemented with oils from three different marine sources, all of which contain high proportions of long-chain n-3 polyunsaturated fatty acids (PUFA), result in qualitatively distinct lipid and fatty acid profiles in guinea pig heart. Albino guinea pigs (14 days old) were fed standard, nonpurified guinea pig diets (NP) or NP supplemented with menhaden fish oil (MO), harp seal oil (SLO) or porbeagle shark liver oil (PLO) (10%, w/w) for 4-5 weeks. An n-6 PUFA control group was fed NP supplemented with corn oil (CO). All animals appeared healthy, with weight gains marginally lower in animals fed the marine oils. Comparison of relative organ weights indicated that only the livers responded to the diets, and that they were heavier only in the marine-oil fed guinea pigs. Heart total cholesterol levels were unaffected by supplementing NP with any of the oils, whereas all increased the triacylglycerol (TAG) content. The fatty-acid profiles of totalphospholipid (TPL), TAG and free fatty acid (FFA) fractions of heart lipids showed that feeding n-3 PUFA significantly altered the proportions of specific fatty-acid classes. For example, all marine-oil-rich diets were associated with increases in total monounsaturated fatty acids in TPL (p < 0.05), and with decreases in total saturates in TAG (p < 0.05). Predictably, the n-3 PUFA enriched regimens significantly increased the cardiac content of n-3 PUFA and decreased that of n-6 PUFA, although the extent varied among the diets. As a result, n-6/n-3 ratios were significantly lower in all myocardial lipid classes of marine-oil-fed guinea pigs. Analyses of the profiles of individual PUFA indicated that quantitatively, the fatty acids of the three marine oils were metabolized and/or incorporated into TPL, TAG and FFA in a diet-specific manner. In animals fed MO-enriched diets in which eicosapentaenoic acid (EPA) > docosahexacnoic acid (DHA), ratios of DHA /EPA in the hearts were 1.2, 2.2 and 1.5 in TPL, TAG and FFA, respectively. In SLO-fed guinea pigs in which dietary EPA ≈ DHA, ratios of DHA/EPA were 0.9, 3.4 and 2.1 in TPL, TAG and FFA, respectively. Feeding NP + PLO (DHA/EPA = 4.8), resulted in values for DHA/EPA in cardiac tissue of 2.1, 10.6 and 2.9 in TPL, TAG and FFA, respectively. In the TAG and FFA, proportions of n-3 docosapentaenoic acid (n-3 DPA) were equal to or higher than EPA in the SLO- and PLO-fed animals. The latter group exhibited the greatest difference between the DHA/n-3 DPA ratio in the diet and in cardiac TAG and FFA fractions (7, 3.4 and 3.1, respectively). Quantitative analysis indicated that ≥ 85% of the n-3 PUFA were in TPL, 7-11% were in TAG, and 2-6% were FFA. Specific patterns of distribution of EPA, DPA and DHA depended on the dietary oil. Both the qualitative and quantitative results of this study demonstrated that in guinea pigs, n-3 PUFA in different marine oils are metabolized and/or incorporated into cardiac lipids in distinct manners. In support of the concept that the diet-induced alterations reflect changes specifically in cardiomyocytes, we observed that direct supplementation of cultured guinea pig myocytes for 2-3 weeks with EPA or DHA produced changes in the PUFA profiles of their TPL that were qualitatively similar to those observed in tissue from the dietary study. The factors that regulate specific deposition of n-3 PUFA from either dietary oils or individual PUFA are not yet known, however the differences that we observed could in some manner be related to cardiac function and thus their relative potentials as health-promoting dietary fats.