Published: May 02, 2011 r2011 American Chemical Society 6284 dx.doi.org/10.1021/jf200686z | J. Agric. Food Chem. 2011, 59, 6284–6291 ARTICLE pubs.acs.org/JAFC Role of the Raw Composition of Pelagic Fish Muscle on the Development of Lipid Oxidation and Rancidity during Storage Rodrigo Maestre,* Manuel Pazos, and Isabel Medina Instituto de Investigaciones Marinas (CSIC), Eduardo Cabello 6, E-36208 Vigo, Spain ABSTRACT: The muscle composition of a pelagic fish species, Atlantic mackerel (Scomber scombrus), has been studied to determine the relationship with its susceptibility to develop lipid oxidation during chilled storage. For such an aim, the initial concentrations of the major components (water, total lipids, protein, and PUFAs) and minor pro-oxidant and antioxidant components (ascorbic acid, R-tocopherol, hemoglobin, total iron, LMW-iron, copper, and zinc) of different batches of mackerel were characterized. For the study, several batches of mackerel were caught during the spring and summer periods. The different batches were subjected to chilled storage, and the onset of lipid oxidation was statistically related with the initial muscle composition. Results showed significant compositional differences among the mackerel lots, especially for the muscle lipid content (2.83À9.50%). In a first step, a Pearson correlation test was used to check the influence of each component on the progress of lipid oxidation. Results showed a significant relationship between shelf life and water and total lipid contents. Multiple regression was performed to reveal the contribution of each component to the susceptibility to lipid oxidation. The model obtained combines the content of PUFAs, total iron, hemoglobin, and ascorbic acid. An accurate prediction of shelf life in terms of rancidity was achieved by the model created (R 2 = 0.9975). These results establish that the levels of endogenous pro-oxidants and antioxidants present in fish muscle together with the polyunsaturated lipids are relevant factors affecting the shelf life of mackerel muscle. KEYWORDS: lipid oxidation, mackerel, Pearson correlation, multiple regressions, shelf life ’ INTRODUCTION Pelagic fish is extremely rich in essential ω-3 polyunsaturated fatty acids (PUFAs) such as eicosapentaenoic acid (20:5ω-3) and docosahexanoic acid (22:6ω-3). Such fatty acids have shown potential benefits for human health. 1,2 However, the oxidative degradation of unsaturated fatty acids is the major cause of quality deterioration in pelagic fish species, leading to the development of rancid off-odors and a reduction of the nutritional value. Lipid oxidation in fish muscle based foods is influenced by external factors such as storage temperature, time, precooking, processing, or packaging. 3,4 Internal factors related to the com- position of muscle also play a key role in the oxidative reaction. According to the radical nature of the reaction, lipid oxidation is sensitive to substances able to catalyze or inhibit the formation of free radicals. In pork, beef, and chicken, the total content of PUFAs together with the presence of pro-oxidant heme proteins and free ionic iron has been suggested to play an important role in lipid oxidation. 5 The different sources of iron and their concentrations have also demonstrated a relative impact on meat lipid oxidation. 6 In these studies the balance between the total antioxidant/pro-oxidant capacities of meat seemed to be sig- nificant for determining the onset of lipid oxidation. Food processing also affects largely the state of intrinsic components. Meat thermal treatments are described to disrupt membranes, release iron, and accelerate the diffusion of reactants, leading to the propagation of oxidation. 7 Studies performed on the oxidation of fish muscle based foods reveal a more complex situation, mainly attributed to a higher proportion and variety of PUFAs 8 and a major pro-oxidant activity of fish hemoglobins. 7 Additionally, pelagic fish species are characterized by huge variations in compositional parameters depending on season and food availability. 9À11 Such variability affects the content of fat and the levels of antioxidants and pro- oxidants. Various attempts using model systems have been made to investigate the role of lipids and promoters of oxidation on the development of lipid oxidation. The elevated susceptibility of fatty fish species to undergo lipid oxidation is often attributed to their intrinsic amount of PUFAs. 12 However, Undeland et al. 13 reported that the incorporation of 15% fish triacylglycerols to washed cod mince did not accelerate the formation of rancid off- odors. In different washed fish mince model systems, the total content of lipids showed a lower contribution than Hb to the development of oxidation. 14 Phospholipids have been denoted the primary substrate for fish lipid oxidation due to their high proportion of PUFAs. 15 Consequently, there is not a clear conclusion about the real influence of fat content on fish oxidation, and which are the decisive components that govern lipid oxidation in fish. Redox active metals such as iron and copper have been also described to enhance lipid oxidation in fish muscle due to their capacity to generate free radicals via Fenton- type reaction or hydroperoxides decomposition. 16 The endogenous antioxidant system of fish that includes lipophilic and hydrophilic compounds has been also shown to influence the onset of fish lipid oxidation. 14 The loss of endo- genous R-tocopherol seems to mark the onset of the propagation phase of lipid oxidation. 17 Other endogenous antioxidants such as ascorbic acid, which is lost in the early post-mortem stages, are important for maintaining of R-tocopherol in its original reduced Received: February 18, 2011 Revised: May 2, 2011 Accepted: May 2, 2011