Numerous analytical methods are routinely used for measuring lipid oxidation in foods. However, there is no uniform and standard method for detecting all oxidative changes in all food systems. Therefore, it is necessary to select a proper and adequate method for a particular application. The available methods to monitor lipid oxidation in foods can be classified into five groups based on what they measure: the absorption of oxygen, the loss of initial substrates, the formation of free radicals, and the formation of primary and secondary oxidation products. A number of physical and chemical tests, including instrumental analyses, have been employed in laboratories and the industry for measurement of various lipid oxidation parameters. These include the weight‐gain and headspace oxygen uptake method for oxygen absorption; chromatographic analysis for changes in reactants; iodometric titration, ferric ion complexes, and Fourier transform infrared (FTIR) method for peroxide value; spectrometry for conjugated dienes and trienes, 2‐thio‐barbituric acid (TBA) value, p ‐anisidine value ( p ‐AnV), and carbonyl value; Rancimat and Oxidative Stability Instrument method for oil stability index; and electron spin resonance (ESR) spectrometric assay for free‐radical type and concentration. Other techniques based on different principles, such as differential scanning calorimetry (DSC) and nuclear magnetic resonance (NMR), have also been used for measuring lipid oxidation. In addition, sensory tests provide subjective or objective evaluation of oxidative deterioration, depending on certain details.

Oxidation of unsaturated lipids is a major cause of food quality deterioration by giving rise to the development of off‐flavor compounds and loss of nutritional value of food products. Antioxidants are substances that, when present in foods at low concentrations compared with that of an oxidizable substrate, markedly delay or prevent the oxidation of the substrate by quenching free radicals or scavenging oxygen, among others. Antioxidants that fit in this definition include free radical scavengers, inactivators of peroxides, and other reactive oxygen species (ROS), chelators of metal ions, and quenchers of secondary lipid oxidation products that produce rancid odors. Antioxidants have also been used in the health‐related area because of their ability to protect the body against damage caused by ROS, reactive nitrogen species (RNS) and those of reactive chlorine species (RCS). The US Food and Drug Administration (FDA) regulates the claim of antioxidants in nutrient labeling. According to FDA, the antioxidant claim is possible only if there is an established reference daily intake (RDI) and a scientific evidence of antioxidative effect after absorption in the gastrointestinal tract.

Marine oils are obtained from the flesh of fatty fish, liver of lean whitefish, and blubber of marine mammals. Lipids from marine fish have been used as food and medicine, and traditional uses of blubber lipids of marine mammals were mostly industrially oriented, except for Innus and Eskimos. Marine mammal oils were used as lubricants or “train” oils as well as fuel and used for lighting. Research findings on the importance of long‐chain polyunsaturated fatty acids (LC PUFA) in human health have opened new channels for their value‐added use in food and pharmaceutical industries. During the last three decades, it has been established that Greenland Eskimos living on their traditional diet have a lower incidence of coronary heart disease than do Danes living on a western‐style diet. It has been recognized that PUFA could be useful in controlling serum triacylglycerols, but the fatty acids provided by the food industry were often of the Ω6 family. This article summarizes the current knowledge available on marine mammal oils with focus on seal and whale oils. It presents the lipid class, fatty acid compositions, and oxidative stability of marine mammal oils. The process, production of omega‐3 fatty acid concentrates, and application of common marine mammal oils are discussed. The health benefits and disease prevention properties of seal oils, especially the two unique ingredients, namely docosapentaenoic acid (DPA) and long‐chain monounsaturated fatty acids, (LC‐MUFA) are reviewed. Finally, the fatty acid profile, position distribution, and health benefits of marine mammal oils are compared with those of fish oils.