Linoleic value chains

It is not certain that the presence of CLA in tissue lipids is due entirely to the production of cis-9, trans-11 as an intermediate during the biohydrogenation of linoleic acid in the rumen. However, the amount of CLA in milk (7 J) and butter (14) is positively correlated to the level of dietary linoleic acid. Some long chain fatty acid intermediates reach the small intestine and are normally absorbed and deposited into adipose tissue (75). There is seasonal variation in CLA content of milk, with the highest values occurring usually in summer (76). 

The occurrence of cis-double bonds hampers dense packing. Trans-double bonds do not have this effect elaldic acid (which has such a bond) packs like stearic acid. The effect of the cis-bond in the hydrocarbon chain is shown in fig. 3.1 lb, where it is observed that in the condensed phase the molecular area of Cj COOH increases from 0.28 nm for the fully saturated hydrocarbon chain (stearic acid), via 0.40 nm for the single unsaturated chain (oleic acid) to 0.49 nm for the doubly conjugated unsaturated chain (linoleic acid). In line with this, the collapse point, i.e. the value for where the monolayer breaks down to form a multilayer. Increases with decreasing degree of saturation. The pressure corresponding to the collapse point is lower when the fatty acid contains more double bonds (see the arrows in the figure). 

However, the situation may be converted in the y-3 form, in which the presence of two cw-double bonds may stabilize the chain-chain interactions of the linoleic acid leaflet, prohibiting the transformation into more stable forms of P or P as illustrated in Figure 9B. For this reason, the A5 value of y of SLS is much larger than those of Y of SOS and SRS. Furthermore, A5 of SLS y is as large as P forms of SOS. Mechanistically, the transformation from y to P or P is associated with an inclined chain arrangement with respect to the lamellar interface (10), which might be prohibited by the chain-chain interactions of the linoleoyl leaflets in SLS. 

Liquid vegetable oil is a mixture of linolenic, lin-oleic, oleic, and stearic esters. The hydrogenation process of these esters displays a chart of a reaction chain shown in Scheme 10. The processes of preferential hydrogenation of more unsaturated acids with minimum formation of completely saturated fatty acids are preferred by the food industry. The selectivity is expressed as the ratio imo/ oie or k o/ko, where the variables k are the reaction rate constants, and the term fiino represents the conversion of linolenic and linoleic compounds, while ole is for oleic. Thus, good processes have high k o/ko values. 

Linoleic acid li-no- le-ik- [Gk linon flax + ISV oleic (acid)] (1857) n. C18H32O2. cisy c/5-9,12 Octadecadienoic acid. An 18-carbon, straight-chain fatty acid with two double bonds that may be in the 9 and 12 or 9 and 11 positions. It is found in nature as its glyceryl trimester in many vegetable oils and is a starting material for some plasticizers for plastics. It has a mol wt of 280.44, bp of 230°C, iodine value of 181.1. 

Rate constants for the above H atom abstraction process are on the order of 10 M" s with the actual values depending both on the nature of the thiyl and the PUFA. For a given thiyl radical the measured rate increases with the number of bisallylic hydrogens. For the reaction of the thiyl radical from glutathione, GS, with PUFAs, for example, the rate constants increase from 0.8 x lO M" s (linoleic acid, 18 2, two double bonds in one bisallylic functionality), over 1.9 x 10 M" s (linolenic acid, 18 3, three double bonds in two bisallylic functionalities), to 3.1 X 10 M s (arachidonic acid, 20 4, four double bonds in three bisallylic functionalities). As expected, the mere length of the aliphatic chain does not play any role, as indicated by identical rate constants for the 18 3 and 22 3 PUFAs. Also, practically no reaction k < 10 M" s" ) is observed for the corresponding reaction of RS with oleic acid (18 1, one double bond) which lacks bisallylic hydrogens. 

The pKs values for the C2-C9 short-chain acid homologues range from 04.75-4.95. The pKg of 7.9 for linoleic acid deviates considerably from this range. This unexpected and anomalous behavior, which has not yet been clarified, is clearly illustrated in the titration curves for propionic, caprylic and linoleic acids recorded under identical conditions (Fig. 3.1). 

The presence of conjugated double bond systems in the alkyl chain increases the retention time of an ester considerably over that of a similar compound with methylene-interrupted double bonds. Methyl 9-c/s,11-frans-octadecadienoate, for example, is a common minor constituent of ruminant and other tissues and has ECL values of 20.48 on EGSS-X and 20.24 on EGSS-Y , i.e. appreciably greater than the corresponding values for methyl linoleate [161]. In addition, the configuration of the double... 

The pH where 50% of an acid is retained in the Upohilic colloidal droplets (1) and the other half is dissolved in the water phase (w), was termed pKi. Dehydroabietic acid having an aromatic ring had the lowest pKi, of 5.3. The other resin acids were rather similar, with pKi values of 6.8-7.1. The pinolenic acid with three double bonds behaved similarly to the resin acids, and linoleic acid similarly to palmitic acid. However, oleic acid dissolved at a clearly higher pH than the polyunsaturated fatty acids. The saturated stearic acid was preferentially in the colloidal phase, even at pH 10. The long-chain fatty acids with 20-24 C-atoms were dissolved only to a small extent, even at pH 11. 

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