Oxidation of fish oil

Since Trolox C favors formation of Cg unsaturated compounds compared to the unsaturated C] q compounds during the oxidation of fish oils (Cg Cio ratio 2.35 Table II), It Is likely... 

Sulf(on)ation is not the only method used to prepare fatliquor from oil. Simple oxidation of fish oil with air or nitric acid is another, again causing a portion of the oil to become amphipathic. The products are often referred to as moellons or degras. ... 

From Frankel etal. (1996b). Oxidation of vegetable oils were carried out at 60°C for 20 days in bulk and for 12 days in emulsions oxidation of fish oil were carried out at 40°C for 10 days. Negative values represent prooxidant activity. 

Jakobsson and Sivik [47] also used ascorbic acid and a-tocopherol as antioxidants to prevent oxidation of fish oil. The a-tocopherol (0.06%) was incorporated in the oil phase, whereas the ascorbic acid was solubilized in the aqueous phase of the w/o microemulsion, whose composition was 77% fish oil, 20% distilled monoglyceride, and 3% aqueous phase. Oxidation was monitored by measuring the peroxide and anisidine values. A drastic reduction in oxidation was observed when antioxidants were incorporated in the microemulsion system. Oxidation was found to decrease further when ascorbic acid was dissolved in glycerol instead of water. A possible reason for this decrease in oxidation is that there is high internal mobility among the molecules and very short distances between the two phases. This promotes the internal mixing and the ability of the antioxidants to meet and scavenge the free radicals. 

Han et al. [48] also studied the effects of various antioxidants such as ascorbic acid, a-tocopherol, and rosemary extract on the oxidation of fish oil and soybean oil using phosphatidylcholine reverse micelles. Peroxide values of the oils indicated that only ascorbic acid (0.02%) solubilized in the reverse micelles was an effective antioxidant in both fish oil and soybean oil. Also, as in the other studies, a combination of ascorbic acid and a-tocopherol was shown to act synergistically in the fish oil. 

K Heinzelmann, K Franke. Using freezing and drying techniques of emulsions for the microencapsulation of fish oil to improve oxidation stability. Colloids Surfaces B Biointerfaces 12(3—6) 223—229, 1999. 

Kagami, Y., Sugimura, S., Fujishima, N., Matsuda, K., Kometani, T., Matsumura, Y. (2003). Oxidative stability, structure, and physical characteristics of microcapsules formed by spray drying of fish oil with protein and dextrin wall materials. Journal of Food Science, 68, 2248-2255. 

The safety of drugs containing EPA and DHA has been reviewed the reported adverse effects were similar to those in control groups (3). Even 3-7 g/day for several months did not change liver enzyme activities, and there were no bleeding problems. Consumption of fish oils reduces the resistance of LDL to oxidative modification, and this is partly opposed by the addition of vitamin E (4). Belching or eructation with a fishy taste or smell, vomiting, flatulence, diarrhea, and constipation are relatively common. 

Erdogan, H., Fadillioglu, E., Ozgocmen, S. etal., Effect of fish oil supplementation on plasma oxidant/antioxidant status in rats, Prostaglandins Leukot. Essent. Fatty Acids, 71, 149, 2004. 

Faraji H, McClements D.J., and Decker EA. (2004). Role of continuous phase protein on the oxidative stability of fish oil-in-water emulsions. J. Agric. Food Chem. 52,4558-4564. 

Heinzelmann, K., Franke, K., Velasco, J., and Marquez-Ruiz, G. (2000). Micro-encapsulation of fish oil by freeze-drying techniques and influence of process parameters on oxidative stability during storage. Fur. Food Res. Technol. 211,234 239. 

Additionally, key secondary oxidation products contribute distinctive aromas characteristic to certain fish species. In salmon, co-oxldatlon of polyunsaturated fatty acids of fish oils with salmon-specific carotenoid pigments leads to the formation of a characterizing cooked salmon flavor compound, and changes the ratio of carbonyl compounds formed compared to that for pure fish oil. 

We originally believed that the short chain saturated fatty acids In oxidizing fish lipids contributed to burnt/flshy flavors. Saturated fatty acid concentrations (C4 - Cg) measured by volatile headspace analysis (32, 59) reached levels as high as 3 ppm In highly oxidized fish oils (32). Flavor threshholds for these short n-chaln fatty acids In oil systems In the literature (>.66 ppm, 63) Indicate that they could contribute notes to oxidizing fish oils. However, studies designed to document the role of short chain acids as flavor compounds detracting from the flavor quality of fish oils did not confirm earlier beliefs. 

The most detailed smdies on the flavor of fish oil in recent years were probably those of Hsieh et al. (78, 79), Lin et al. (80), and Lin (81). In their studies, a series of alkanals, alkenals, alkadienals, and alkatrienals were determined by dynamic headspace gas chromatography-mass spectrometry in cmde menhaden oils (Table 11). Most of these aldehydes contributed to the characteristic oxidized oily odors, such as green grassy, waxy, and rancid in the crude oils. Alkatrienals, i.e., nonatrienal and decatrienals, were also found at ppb levels in the dynamic headspace of the crude oils. 2-fraM5,4-frflMi,7-cA-Decatrienal, 2-fra 5,4-d5,7-di-decatrienal,... 

Oxidative stability of 00-3 fatty acids can be increased using free radical scavengers. TBHQ (t-butyUiydroquinone) at a concentration of 0.02% has successfully slowed down the oxidation of menhaden oil for up to 40 days, compared with 3 days for the control group (83). a-Tocopherol and butylated hydroxytoluene (BHT) alone or in combination increased the oxidative stability of EPA and DHA (84). The most notable success in fish oil stabilization has been achieved with ternary antioxidant systems, which contain a- or y-tocopherol concentrates, ascorbic acid (or ascorbyl palmitate), and lecithin (85). 

This equation was originally developed to express the inactivation kinetics of a-chymotrypsin and glucoamylase covalently bound to a water-insoluble support in an aqueous system (Kawamura et al., 1981). Equation 1.4 was successfully applied to express the oxidation kinetics of fish oil (EPA, eicosapentaenoic acid Yoshii et al., 2003) and linoleic acid powder (Ishidoh et al., 2002, 2003). The above-mentioned three equations are equivalent from the perspective of simulation of flavor release from spray-dried powder. All of the parameters, n in Equation 1.1, (3 in KWW s equation, and a Gaussian distribution with the standard deviation o in Equation 1.4, can be viewed as a consequence of the activation energy distribution of the release rate. 

Vogt, G., Aursand, M., Aaby, K., and Nilsson, A. 2001. Evaluation of conventional methods for measuring oxidation in fish oil, Lipidforum, 21 stNordic Lipid Symposium, Bergen, June 5-8, 2001. 

It has to be remembered that the results of in vitro and ex vivo studies on the effect of n-3 LC-PUFA on LDL oxidation are equivocal. Many studies showed either no LDL oxidation under fish oil (27-32), or even a decrease in the rate and the extent of oxidation (33,34). These seemingly contradictory findings may be related to the methodology of measuring LDL oxidation, as well as to the actual variable chosen to evaluate LDL susceptibility. To what extent oxidative susceptibility of LDL measured ex vivo reflects oxidative susceptibility in vivo is unknown. 

Sorensen, N.S., Marckmann, P., Hoy, C.E., van Duyvenvo-orde, W., and Prince, H.M. (1998) Effect of Fish-Oil-Enriched Margarine on Plasma Lipids, Low-Density-Lipoprotein Particle Composition, Size, and Susceptibility to Oxidation, Am. J. Clin. Nutr. 68, 235-241. 

Wander, R.C., Han, C.-T., Lee, Y.-S., and Caputa, M.D. (2002) Dose-Dependent Effects of Fish Oil on LDL and HDL Oxidative Susceptibility and Functional Properties. 5th Congress of the International Society for the Study of Fatty Acids and Lipids (ISSFAL), May 7-11,2002, Montreal, Canada. 

Drusch S, Serfert Y, Scampicchio M et al. (2007) Impact of physicochemical characteristics on the oxidative stability of fish oil microencapsulated by spray-drying. Journal of Agricultural and Food Chemistry 55 11044-11051. 

Drusch S, Serfert Y, Schwarz K (2006) Microencapsulation of fish oil with n-octenylsuccinate-deriva-tised starch Flow properties and oxidative stability. European Journal of Lipid Science and Technology 108 501-512. 

Hughes BH, Muzzy HM, Laliberte LC, Grenier HS, Perkins LB, Skonberg DI. Oxidative stability and consumer acceptance of fish oil fortified nntrition hax. J Food Sci. 77(9) (2012) S329-S334. 

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