Lipids and their constituent fatty acids are, along with proteins, the major organic constituents of fish, and they play major roles as sources of metabolic energy for growth including reproduction and movement, including migration. Furthermore, the fatty acids of fish lipids are rich in ω3 long chain, highly unsaturated fatty acids (n-3 HUFA) that have particularly important roles in animal nutrition, including fish and human nutrition, reflecting their roles in critical physiological processes. Indeed, fish are the most important food source of these vital nutrients for man. Thus, the longstanding interest in fish lipids stems from their abundance and their uniqueness. This review attempts to summarize our present state of knowledge of various aspects of the basic biochemistry, metabolism, and functions of fatty acids, and the lipids they constitute part of, in fish, seeking where possible to relate that understanding as much to fish in their natural environment as to farmed fish. In doing so, it highli...

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Metabolism and Functions of Lipids and Fatty Acids in Teleost Fish

https://dspace.stir.ac.uk/bitstream/1893/467/1/Tocheretal2008.pdf

The role of phospholipids in nutrition and metabolism of teleost fish

Dietary sunflower oil (SFO) was used to gradually replace fish oil (FO) in six diets (which also contained fish meal) for Atlantic salmon parr (initial mass: 21.7 g). The effect on growth performance, tissue fatty acid profiles and disease resistance was monitored after 63 days. At the conclusion of the trial, no significant differences were detected in growth between any of the feeds. Fatty acid composition of whole carcass, dorsal muscle and liver generally reflected that of the diets. Forty percent of the FO could be replaced by SFO before tissue 22:6n-3 was significantly reduced, although other essential and non-essential fatty acids were more susceptible to change. Significant differences were detected in cumulative mortality of Atlantic salmon challenged with Vibrio anguillarum at the trials conclusion, although this was not correlated to the inclusion level of SFO. Despite the changes observed to the tissue fatty acid profile, there was no significant effect on growth suggesting that SFO is a suitable alternative to FO in diets for Atlantic salmon parr when fish meal is also included.

Replacement of fish oil with sunflower oil in feeds for Atlantic salmon (Salmo salar L.): effect on growth performance, tissue fatty acid composition and disease resistance.

Lipid oxidation is an important cause of quality deterioration in seafood, particularly those products which contain high concentrations of lipid. Although this is a primary deteriorative reaction in many types of food, it is particularly acute in fish because of the high content of highly polyunsaturated fatty acids found in organisms from the marine environment (Ackman, 1980). The free radical mechanism of lipid oxidation involving initiation, propagation, and termination steps is familiar (Khayat and Schwall, 1983;Frankel, 1985). Recent kinetic models for lipid oxidation in a variety of food products and biological tissue have shown excellent agreement with chemical measurements of oxidation based on this free radical mechanism (Tappel et al.,1989;Ozligen and Ozligen, 1990). In this paper inhibitors and activators of lipid oxidation will be discussed, with their likely contribution to seafood oxidation. Some general methods for limiting the rate and/or extent of lipid oxidation will also be considered.

Oxidation of lipids in seafoods

Fish and marine invertebrates are an important part of our diet as they contribute to the intake of health‐pro omega‐3 fatty acids and possibly to prevention and treatment of coronary heart diseases. The crude protein contents of seafoods generally vary between 11.0% and 28.4% (usually about 19.0%), and the content of lipid in muscle tissue is inversely related to its moisture content. The contribution of non‐protein nitrogenous compounds to the total crude protein content of seafoods depends on the species of raw material and range from 10% to 40%. While the amount of fat‐soluble vitamins in seafoods is often higher than those in land animals and depends, to a large extent, on the species, the content of water‐soluble vitamins in seafoods is less dependent upon the species. The content of minerals in seafoods is slightly higher than those in terrestrial animals. The flavor of seafoods depends on the species, the fat content, and the presence as well as the type of nonprotein nitrogenous compounds.

Structure and composition of fish muscle

Lipolysis occurs extensively in fish muscle post-mortem and is associated with quality deterioration in the frozen tissue. Fish muscle lipolysis is presented in the context of basic fish muscle physiology and lipid composition. Phospholipase A and lipases from fish muscle have been described and characterized. The reaction is usually followed by measurement of free fatty acid production, and several colorimetric assays are available. Processing and storage treatments have been shown to influence the extent and rate of lipolysis in fish muscle; most of the research in this area has been directed at the effects of frozen storage. The interaction of lipolysis and lipid oxidation is a particularly intriguing area of study as triglyceride hydrolysis leads to increased oxidation while phospholipid hydrolysis produces the opposite effect.

Robert L. Shewfelt

Papers

Fish muscle lipolysis—a review

Sarcoplasmic reticulum from flounder muscle having improved lipid peroxidative activity.