Oxidation in fish lipids during thermal stress as studied by 13 C nuclear magnetic resonance spectroscopy (original) (raw)
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Journal of The American Oil Chemists Society, 1998
13C Nuclear magnetic resonance spectroscopy has been applied to elucidate the mechanism of lipid oxidation occurring during thermal treatment of fish. Effects of temperature and time of processing have been studied by means of a model system of lipids, extracted from salmon (Salmo salar) muscle, to simulate industrial conditions of canning. Unsaturated fatty acids located at the sn-2 position of the glycerol moiety were the most prone to oxidative damage. Regarding the mechanism of the reaction, results inferred from olefinic and methylenic resonances indicated a higher susceptibility of the allylic sites closest to the carbonyl group, followed by those placed near the methyl terminal group. Unsaturations located in the middle of the carbon chain did not show much damage. The glyceryl region provided an unusual resonance at 53.4 ppm, which could be assigned to a hydroxylic compound formed during process.
Relationship between lipid and protein oxidation in fish
Aquaculture Research
Oxidation in food is a process that concerns both lipids and proteins by the effect of reactive oxygen species (ROS) (Bernardini et al., 2011). Oxidative modifications can cause numerous functional consequences and lead to changes in food texture, water holding capacity (WHC), digestibility and juiciness in fish meat (Baron, Kjaersgard, Jessen, & Jacobsen, 2007). Also, Sarma, Reddy, and Srikar (2000) found a negative correlation between lipid oxidation parameters and functional properties of the protein in Indian oil sardine, indicating their interdependence. However, still little is known about the kinetics of protein oxidation, the interaction of protein and lipid oxidation and the subsequent impact on muscle food quality (Baron et al., 2007; Kjaersgard & Jessen, 2004). For many years, the focus of food was on lipid oxidation, not only because of its effect on taste and shelf life, but also because the lipid oxidation products can more easily be measured (hydroperoxides, hexanal and MDA) than protein oxidation product and therefore have been detected and correlated to off-flavour in food. Especially in fish, which is rich in n-3 polyunsaturated fatty acids (PUFA), there is a high risk of quality loss due to oxidation (Jeremiah, 2001; Medina, Gallardo, & Aubourg, 2009). Besides lipid oxidation, the oxidation of proteins can also cause quality changes in the fish fillet. In general, the same factors causing lipid oxidation will also cause protein
Biofactors, 2005
Numerous changes occur post-mortem in fish, affecting its chemical composition and nutritional quality. In the present paper we describe the effect of storage on ice or at −30°C or −80°C on 10 species of Mediterranean fish. Water and lipid soluble antioxidants, lipid pattern and products of oxidative attack on lipids, proteins and DNA were quantified for 7 consecutive days on homogenates of fish light muscle. The earliest events were oxidation of ubiquinol and vitamin C, which disappeared almost completely within 48 hours. Ubiquinol oxidation gave rise to an initial increase of ubiquinone, which peaked at the second day: thereafter ubiquinone itslef decreased, more rapidly and to a greater extent than vitamin E. The decrease in antioxidants was accompanied by significant oxidative damage to lipids, proteins and DNA. TBARS significantly increased beginning from the third day of storage in all species and were linked to a significant reduction in the n-3 PUFA of triglycerides (TG) and phospholipid fractions (PL). A remarkable elevation of protein carbonyls and 8OHdG occurred approximately 24 hours later than PUFA oxidation. For SOD, GPX and GSH significant depletions occurred for all species only at 6th or 7th day, but the final values were always higher than 50% compared to the initial ones.Deep-freezing of the same species at −30°C and −80°C for up to 12 months did not significantly affect the levels of enzymatic antioxidants, the redox couple GSH/GS-SG, n-3 and n-6 PUFA of TG and PL fractions of the light muscle.The only antioxidants, which at −30°C and −80°C appeared to be degraded after 6 and 12 months were ubiquinol and vitamin C. As expected their degradation was higher at −30°C than at −80°C. In fact the average decrease for ubiquinol at −80°C was 42% at 6 and 12 months respectively, whereas at −30°C the decrease was 61% and 87% For vitamin C the average decrease at −80°C was 36% and 67% at 6 and 12 months respectively, and at −30°C it was 61% and 82%.Vitamin E was considerably more stable than ubiquinol and vitamin C. The relative stability of the antioxidants, with the exceptions of ubiquionols, vitamin C and, to a certain extent, vitamin E, was accompanied by a very limited increase in oxidation products.In addition no significant hydrolysis of TG and PL fractions were observed throughout the storage time.The dynamics of lipid, protein and DNA oxidation is discussed in the light of depletion of the various antioxidant systems.
13 C nuclear magnetic resonance monitoring of free fatty acid release after fish thermal processing
Journal of The American Oil Chemists Society, 1994
13C Nuclear magnetic resonance spectroscopy was applied to the study of lipid hydrolysis occurring during industrial canning of tuna (Thunnus alalunga). An increase in the free fatty acid (FFA) level was observed after cooking and sterilization, and a different FFA pattern was found when storage of the frozen raw material and thermal steps (cooking and can sterilization) were compared. Lipolysis in raw muscle occurs preferentially in thesn-1 andsn-3 acyl positions of triacylglycerols, with a consequent cleavage of saturated and monounsaturated fatty acids. After thermal processing, an increase of docosahexaenoic acid (DHA) was found in the FFA fraction, as well as a relative decrease of the peak intensity of DHA in thesn-2 position of triacylglycerols. This finding indicates a different mechanism of FFA release during the frozen storage and thermal processing of raw fish.
From farm to fork: lipid oxidation in fish products. A review Giulia Secci & Giuliana Parisi
Lipid oxidation is a very complex and important event threatening the quality of foods especially of those containing highly unsaturated fats. Fish are the main source of polyunsaturated fatty acids that, unfortunately, are highly susceptible to degradation process, such as oxidation. Fish supply chain generally involves many steps and each of them together with their interaction might play a central role in muscle quality maintenance. From this review emerged that antioxidants supplementation diet can play a central role to limit the detrimental effects of stress (preslaughter or at killing) and storage. In this sense, lycopene shows the best antioxidant activity during stressful conditions while a-tocopherol acts preferentially in long-term frozen storage. Stress just before or at slaughter can greatly threaten flesh quality both immediately and after storage by inducing numerous metabolic pathways, that often involve the production of very reactive molecular species, such as hydroperoxides. A common operation such as bleeding can significantly reduce both reactive molecules and haemoglobin (Hb), which is recognised as a great pro-oxidant. Temperature and duration are two critical points of storage phase which has to be considered even by consumers. Frozen storage at very low temperatures (À30 C, À40 C) confirms to be the best storage practise. Finally, cooking can compromise aromatic profile of cooking fillets. Thus, feeding antioxidant, reducing stress both during pre-slaughter practise and at killing, good storage practises, if associated with an appropriate cooking method (low temperature, short time) seems to be the clues for preserving the fragile lipid fraction from farm to fork.
Food Control
The aim of this study was to assess lipid oxidation development in sous-vide cooked Atlantic mackerel during chilled storage by fluorescence microscopy coupled with chemical, physical and data analysis methods. Sous vide-cooking at 70°C and 80°C for 10 and 20 min was performed with and without use of antioxidants. Fluorescence micrographs of lipids extracted from the fish samples on 1st, 3rd, 7th, and 9th day of chilled storage at 4 ± 1°C, were acquired in the wavelength region of λex 475/40 and λem 530/50 (44 FITC filter). The obtained images were numerically processed and the resulting data correlated with 2-thiobarbituric acid reactive substances (TBARS) determined by conventional chemical method of lipid oxidation analyses. Total lipid content and color characteristics of mackerel fillets were analyzed as well. The yellowness of the fish flesh significantly correlated (p < 0.05, R = 0.859) with conjugated trienes generated from thermal polymerization of lipids during chilled storage of sous-vide cooked mackerel. Results showed that higher temperature and cooking times generally accelerated lipid oxidation in mackerel samples prepared both with and without addition of antioxidants in terms of conjugated trienes and tetraenes. However, the addition of antioxidants enhanced the lipid oxidation stability of cooked mackerel fillets.