Eicosapentaenoic acid oxidative stability

FA distribution in TAG as well as in phospholipids affects the physical properties, lipolitic and oxidative stability, and nutritional availability of lipids. In many TAG, the FA are arranged in a nonrandom distribution. In plants, monoenoic FA and PUFA are dominant at a sn-2 position (Orthoefer, 1996). In pig depot fat and in cow s milk, the TAG sn-2 position is occupied by palmitic acid. The distribution is also different in cattle and sheep depot fats (Love, 1996). In blubber seals, long-chain n-3 PUFA are esterified rather in sn-l,3 positions, whereas, in muscle, TAG in the sn-2 position that is typical for the lipid muscles of nearly all fish (Ackman, 1994). Enzymatic syntheses of structured TAG containing dY-5,8,ll,14,17-eicosapentaenoic acid (EPA) and dY-4,7,10,13,16,19-docosahexaenoic acid (DHA) in the sn-2 position with medium-chain FA at the end positions are particularly interesting (Halldorsson... 

Production of TAG enriched with polyunsaturated fatty acids (PUFA) via lipase catalysis in codliver oil has also been described (Haraldsson et ah, 1989). Preparation of y-linolenic acid enriched TAG via rapeseed lipases (Syed Rahmatullah et aL, 1994 Jachmanian and Mukerjee, 1996) and microbial lipases (Akoh et aL, 1995, 1996) has also been reported. Incorporation of eicosapentaenoic and docosahexaenoic acids into peanut oil via transesterification catalysed by microbial lipases has been reported by Sridhar and Lakshminarayana (1992). According to Wada and Koizumi (1986) and Kimoto et aL (1994) interesterification of fish oils to form TAG containing PUFA in the 2-position rather than the 1,3-positions increases the oxidative stability of the modified oil as compared to its original counterpart. 

There is evidence that humans benefit from diets with additional fatty acids that have a double bond three carbons from the methyl end of the chain, the so-called n-3 or o)-3 fatty acids, such as the eicosapentaenoate of fish oil or the linolenate of soybean and canola oils. These results have led some people to question the desirability of reducing linolenate percentages to increase oxidative stability and even to suggest that consumers might benefit from raising the linolenate level of soybean oil. A ratio of linoleate to linolenate of 4 1 has been suggested as ideal (Chapkin, 1992 Bruckner, 1992). Since soybean oil is the major oil... 

Unsaturated fatty acids such as DHA (mentioned earlier), eicosapentaenoic (EPA), arachidonic, y-linolenic and linoleic acids, and their alkali metal salts or esters are unstable, since air oxidation easily occurs at the double-bond site. Hence, plant and fish oils, which contain many triglycerides with a high proportion of unsaturated fatty acids, are easily oxidized, resulting in loss of stability in storage. It was considered difficult to stabilize triglycerides with CyDs since triglycerides are large molecules, but the use of y-CyD has allowed plant and fish oils to be stabilized [22]. 

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