Oxidation linolenic acid

That lipid alkoxyl radicals recombine (Reaction 71) at diffusion controlled rates (k= 10 M s ) (198, 305) probably accounts for the presence of low levels of peroxides even under mild conditions and low levels of oxidation. In one study, oxidation of linoleic acid at 30°C gave —C—O—O—C— dimers. Reactions 71-73 were found in linolenic acid oxidized under mild conditions to PV 585 this increased to > 50% at PV 4000 and to > 75% after heating to 40°C (276). Alkoxyl radicals from hydroperoxyepidioxides heated at 40°C generated > 90% dimers (276). 

Small-molecular-weight copper complexes also inhibit lipid peroxidation. The oxidation of linolenic acid by the xanthine oxidase-acetaldehyde superoxide generating system was prevented by Cu(II)2(lonazolac)4 [194]. This eom-plex was also effective in inhibiting linolenic acid oxidation in the presence of... 

Some types of fatty acids and minor constituents are more beneficial in inhibiting oxidation in oils than others. As mentioned previously, polyunsaturated fatty acids such as linolenic acid oxidize easily and are undesirable in edible oils because of the off-flavors and potentially harmful comlb formed. However, linolenic acid is an omega-3 fatty acid that is shown to have positive health effects (Frankel, 2005). Food scientists recommend lower levels of 2—3% linolenic acid, but not complete removal. Tocopherols are another example of the paradox of food constituents. Although alpha... 

Antioxidative activities of the hydrolysates from porcine myofibrillar protein were measured in a linolenic acid oxidation system The hydrolysates at the concentration of 0.02, 0.2 and 2% exhibited antioxidative activities. All hydrolysates exhibited stronger antioxidative activity, as the concentration was higher in the production of hydroperoxides. On the other hand, the addition of 0.2% hydrolysate suppressed the production of TEARS most strongly, and the antioxidative activity in the addition of 2% hydrolysate was lower than that of 0.2% in the method of TEARS. It is well known that 2-thiobarbituric acid (TEA) reacts with aldehyde compounds including malondialdehyde (MDA) formed by Upid peroxidation. Two percent hydrolysates contained a lot of amino confounds including free amino acids and peptides. Therefore, the production of aldehyde compounds seems to be accelerated by amino-carbonyl reaction between hydrolysate and lipid in lipid peroxidation system including 2% hydrolysate. This might be the reason why the antioxidative activity of 2% hydrolysate was lower than that of 0.2 % hydrolysate in the method of TEARS. 

Write properly balanced chemical equations for the oxidation to COg and water of (a) myristic acid, (b) stearic acid, (c) a-linolenic acid, and (d) arachidonic acid. 

Meadows, J., Smith, R.C. and Reeves, J. (1986). Uric acid protects membranes and linolenic acid from ozone-induced oxidation. Biochem. Biophys. Res. Commun. 137, 536-541. 

The major fatty acids present in plant-derived fatty substances are oleic acid (9-octadecenoic, C18 l), linoleic acid (9,12-octadecadienoic, C18 2) and the conjugated isomers thereof and linolenic acid (9,12,15-octadecatrienoic, C18 3) (Scheme 31.1). Their rates of oxygen absorption are 100 40 1, respectively, hence partial hydrogenation with consequent lowering of the iodine number would lead to a significant increase in oxidative stabihty, particularly when C18 3 is reduced. 

The unsaturated fatty acid oxidation proceeds at a rate higher over that for saturated acids. For example, if the oxidation rate for saturated stearic acid is taken as a reference value, the oxidation rate for oleic acid is i 1 times, linolic acid, 114 times, linolenic acid, 170 times, and arachidonic acid, nearly 200 times as high as that for stearic acid. 

The profile is characterized by substantial amounts of dicarboxylic acids, mainly formed in the oxidation of polyunsaturated Cl8 acids (linoleic acid, 08 2 and linolenic acid, 08 3), which are no longer detected after ageing. The presence of short chain dicarboxylic acid, and in particular of oxalic acid, is also characteristic of aged lipid layers. Moreover, in the 30 35 min interval, several peaks are detected and attributed to oxidized species of unsaturated 08 acids. Figure 7.7 reports the mass spectrum of the peak at 31.84, attributed to 13-OH-9-octadecenoic acid or 14-OH-9-octadecenoic acid. Its... 

Other octadecenoic acids carrying hydroxyl groups in the chain are present in the considered time range their formation derives from the oxidation of the unsaturated Cl8 FAs linoleic acid, linolenic acid and oleic acid. 

Carrots (Daucus carota) are excellent sources of (3-carotene and vitamin A, although they have been reported to exert low antioxidant activity compared to some other vegetables (Al-Saikhan and others 1995 Cao and others 1996 Ramarathnam and others 1997 Vinson and others 1998 Beom and others 1998). However, boiling carrots for 30 min significantly improved their antioxidant activity toward coupled oxidation of (3-carotene and linolenic acid (Gazzani and others 1998). 

Interestingly, the first biosynthetic experiments with [3H]linolenic add and the terrestrial plant Senecio isatideus (Asteraceae) as a model system for the biosynthesis of algal pheromones were unsuccessful. If, however, labeled dodeca-3,6,9-trienoic add is administered, a rapid transformation into ectocarpene takes place (36). Nevertheless, the C12 add ultimately derives from linolenic acid via three /3-oxidations, since labeled tetradeca-5,8,11-trienoic acid, which requires only one /3-oxidation, is converted into labeled ectocarpene albeit with very low effidency (37). 

Odor and color stability problems were also related to the alkyl chains used for SAI. These could be traced to the oxidation of unsaturated carbons, such as oleic acid (Ci8 fatty acid with a single double bond between carbon 9 and 10, i.e. bond position 9 counted from the carboxyl carbon), linoleic acid (Cis fatty acid with two double bonds at position 9 and 12), and linolenic acid (Cis fatty acid with three double bonds at position 9, 12, and 15). Natural coconut fatty acid contains about 6% oleic acid, about 3% linoleic acid, and less than 1% linolenic acid. Tallow fatty acid contains nearly 44% oleic and about 6% of other unsaturates [20]. Partial hydrogenation of the coconut fatty acid used in the manufacture of SCI served to eliminate linoleic and linolenic acids for improved odor stability, while not eliminating oleic acid, which is important for good lather. 

As shown in Table 1, the acyl moiety of cardiolipin is comprised almost entirely of unsaturated fatty acids. Other membrane phospholipids such as phosphatidyl choline and phosphatidyl ethanolamine contain 1(M0 mol of saturatedfatty acids such as palmitic acid (Ci6 0) and stearic acid (Ci8 0) per 100 mol of total fatty acids. In particular,linoleic acid (Cl8 2) is the most abundant polyunsaturated fatty acid consisting of 80 mol%, linolenic acid (Cl8 3) 8 mol%, and oleic acid (Ci8 i) 6 mol%. Therefore, by using a commercially available cardiolipin purified from bovine heart mitochondria, we characterized auto-oxidation products by reverse phase HPTLC and reverse phase HPLC. 

The concentration of ozone taken up by the media containing linolenic acid is plotted against time after addition in Figure 8. The rate of ozone breakdown is constant (ozone uptake linear with time) for the first two min until about 0.12 ml ozone are absorbed and then the rate decreases sharply, reaching a steady-state rate of ozone uptake between 10-12 min. This first break in the curve corresponds to an ozone uptake of 0.12 ml + (24 moles/liter) = 0.005 millimoles (or 10 M). This is equivalent to 1 mole of linolenic acid added per mole ozone absorbed. Thiobarbituric acid reactant production is also plotted on the same axis. This compound (TBA reactant) probably arises by formation of a three-carbon fragment (malondialdehyde) from the ozone-induced oxidation of linolenic acid (23). The rate of TBA reactant formation is also linear for the first 2 min at which point the curve undergoes a less pronounced break. Malondialdehyde formation ceases immediately when the ozone is shut off (Scrub 1 on). An oxygen control sample produced no malondialdehyde. 

The correlation between the TEARS assay and MDA dnring oxidation of edible oils may be complicated by the presence of tocopherols (e.g. Vitamin E, 21) . An evaluation was carried of MDA, determined by an independent method , and TEARS as indices for direct oxygen uptake of edible oils and unsatnrated fatty acids. The linear increase of MDA and TEARS with oxygen consumption of soybean oil, in a closed vessel at 170 °C, stops when the latter value reaches 500 p.molL, when both MDA and TEARS start to decrease on further O2 consumption. The same process carried out at 40 °C, using 2,2 -azobis(2,4-dimethylvaleronitrile) (171) as initiator, shows linearity up to 1500 p,molL O2 consumption . A similar behavior is observed for nnsatnrated fatty acids snch as oleic, linoleic and linolenic acids . On the other hand, depletion of Vitamin E (a-tocopherol, 21) and its analogs y- and 5-tocopherol (172, 173) present in the oil show a linear dependence on O2 consumption of the oil, np to 1800 p,molL . This points to the consumption of these antioxidants, and especially 21, as a good index for the O2 uptake in oils at high temperature. The determination of the tocopherols is carried ont by HPLC-FLD (Xex = 295 nm, Ah = 325 nm) . ... 

Linalool, cis, oxide 0 , 1 S172 Linalool, trans, oxide 1 3172 Linalool Pi , Resin , Lf 0 ° Linoleic acid methyl ester 1 73172 Linoleic acid 1 73172 gjCSl34 Linolenic acid methyl ester 0 Linolenic acid 1 3172 gjCSl34 Longifolene, (+) 1 3068 Longifolene 1 3172 qCS156 Inflorescence... 

The flavour of distillates from apple and pear is characterised by typical aroma compounds from these fruits formed by enzymatic degradation of fatty acids to C6-fragments like hexanol, trans-2-hexenol, as well as ethyl esters and acetates of hexanoic acid. In distillates of pears, especially of the variety Bartlett pear, the characteristic pear flavour is mainly dominated by the ethyl and methyl esters of frans-2-czs-4-decadienoic acid and trans-2-trans-A-decadienoic acid [27-29], The biogenesis of these monounsaturated, diunsaturated, and triunsaturated esters may be explained by -oxidation of unsaturated linoleic and linolenic acid in the fruits. The sesquiterpene compound a-farnesene, which is formed during postharvest ripening and storage of Bartlett pears [28], shows that quality and intensity of distilled pear spirits is mainly influenced by the quality and degree of ripeness of the fruits. 

In plants the 13-hydroperoxide produced from linolenic acid by lipoxygenase (Sect. 23.4.1.2) can be converted to the allene oxide by allene oxide synthase followed by cyclisation, reduction and -oxidation to form jasmonic acid, an important plant growth factor the corresponding methyl jasmonate is a valuable flavour and fragrance compound that imparts a sweet-floral, jasmine-like note... 

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