Linolenic iodine value

As a reference, the iodine values of oleic, linoleic, and linolenic acids are 89.9, 181.0, and 273.5, respectively. Iodine values for free fatty acids are higher than for those that are part... 

Oxidation Stability (OSI or Rancimat) has been introduced in many ways. In EN14214 it exists as OSI and as a maximum acceptable Iodine Value, or maximum level of linolenic acid or of poly-unsaturated fatty acids. Oxidation stability is of importance when it comes to polymerization and oxidation during storage as well as during use in the engine. Oxidation is directly related to the presence of unsaturated bonds in the FAME, and probably because of this the EN 14214 includes a cap on Iodine Value. 

Is the Iodine Value found in EN 14214 based on science It is certainly not so in an absolute way, but some relation cannot be denied. Frankel (2005) for example clearly states that oxidation stability is a function of two things the number of double bounds, and their position towards one another in the fatty acid. Oleic acid with one double bound oxidizes 40 times slower than linoleic acid with two double bounds, and one bis-allylic position in-between both. Linolenic acid with three double bounds separated with two bis-allylic positions oxidizes only 2.5 times faster than linoleic acid. Oxidation is a radical driven reaction, and the bis-allylic positions are a much more favorable point of attack than the allylic positions next to the double bound. 

The weight of bromine is independent of the amount (per cent) of linolenic acid in the sample, but it varies with the iodine value. For the purposes of this experiment the amount of bromine (grams) may be calculated as 0.7 times the iodine value of the oil. This allows an excess of 10-11 per cent. 

The higher value for canola oil is caused, in part, by the replacement of erucic acid with octadecenoic acids, mainly oleic acid, accompanied by a slight increase in linoleic and linolenic acids (Table 13). The iodine value can also be calculated from fatty acid composition using the specific factors for each unsaturated fatty acid (61). The calculation method provides more accurate data than the iodine absorption assessment. 

The seed of perilla contains 31-51% of oil, which is similar in composition to flaxseed oil, with a higher contribution of PUFA of over 70% (Table 4). The oil is highly unsaturated, with an iodine value of 192-208-g iodine /100-g oil (Table 4). Perilla oil contains over 60% linolenic acid with equal amounts of both linoleic and oleic acids (Table 4). Specific gravity of this oil is higher than flax oil because of a higher contribution of PUFA. Other physical parameters of this oil reflect the composition of its fatty acids. 

Watermelon seed oil was prepared and evaluated for its physicochemical properties (22, 23). The seed oil consisted of 59.6% linoleic acid (18 2n-6) and 78.4% total unsaturated fatty acids (Table 4). The predominant fatty acid in the oil was linoleic acid, which was followed by oleic, palmitic, and stearic acids. Linolenic, palmitoleic, and myristic acids were minor constituents. The refractive index, acid value, peroxide value, and free fatty acids of watermelon seed oil were determined to be 1.4696 (25°C), 2.82 (mg KOH/g oil), 3.40 (mequiv oxygen/kg oil), and 1.41 (% as oleic acid), respectively. The saponification value of watermelon seed oil was 201 (mg KOH/g oil), and its iodine value was 115 (g iodine/100-g oil), which was significantly higher than pumpkin at 109 (g iodine/lOO-g oil) (22, 23). 

The triglycerides of linseed reflect its high linole-nate composition. A wide variation in linolenate content has been noted (Table 3.62). This is related both to variety and to climatic conditions during maturation, the colder the climate the higher the iodine value. Early work (Dillman and Hopper, 1943) has also shown that moisture deficiency during growth tends to reduce the iodine value. There is a close correlation between refractive index and iodine value (Zeleny and Coleman, 1936) (see also Schuster and Marquard, 1974). 

Soybean oil shows a wide variation in composition (Table 3.113). Strong interrelationships exist between the fatty acids. Linolenic and linoleic acids are directly correlated, linolenic and oleic acids are negatively correlated. Saturated acids range from 11 to 26% and are virtually independent of the iodine value (Howel and Collins, 1957 Sing, 1976 White etaly 1961). 

Because linolenic acid (a minor but significant component of soybean oil) with its n—3 (A 15) double bond furnishes undesirable flavours after oxidation and also because linoleic acid has a desirable dietary value considerable effort has gone into making catalysts with high linolenic/linoleic selectivity. For nickel catalyst this is only 2-3 but with copper catalysts it may be 15-20. Thus soybean oil, reduced to an iodine value of 110 for use as a salad oil, would contain <1% or 4-5% linolenate with copper or nickel catalysts respectively. 

Cedar nut oil n. Pinus cembra, from the seeds of which this oil is derived, grows prolifically in several parts of the world. The main constituent acids are linoleic, linolenic, and oleic acids, and the oil possesses useful drying properties. Iodine values up to 160 have been reported. 

Hempseed oil n. A semidrying oil obtained from the seeds of Cannabis sativa, which grows in India, Manchuria, China, Japan, and some parts of Europe. It is usually classed with soybean, poppyseed, sunflower, and walnut oils, and has an iodine value of approximately 160, arising in the main from the presence of practically 50% of linoleic acid and 25% of linolenic acid. It has some application in manufacture of paints and varnishes. 

Lallemantia oil Drying oil obtained from the seeds of Lallemantia iberica, found in parts of Asia and Europe. It has Sp gr of 0.934/20°C, iodine value of 190, and saponification value of 190. Its main constituents are linolenic and linolenic glycerides. 

Perilla oil p9- ri-l9 (1917) n. A drying oil obtained from the seed of the perilla plants, Perilla ocymoides and Perilla nankinensis, natives of the Orient. Its main constituent acids are linoleic and linolenic, and it has the highest iodine value of all known vegetable oils except chia. It is superior to linseed oil, both from the point of view of drying rate, especially in the form of stand oil, and also of polymerization rate. Sp gr, 0.933-0.937 per 15°C iodine value, 194, saponification value, 192. Paint pigment, drying oils, polymers, resins, naval stores, cellulosics esters, and ink vehicles, vol 3. American Society for Testing and Material, Philadelphia, PA, 2001. 

Safflower oil sa- flau(-9)r- (ca. 1857) n. Semidrying to drying oil, obtained from Carthamus tinctorim, a native of India. It is now available from seed grown in USA. Its main constituent acid is linoleic, with a small quantity of linolenic acid. It dries and bodies more slowly than linseed oil. Sp gr, 0.925/15°C iodine value, 139 saponification value, 189. Its drying characteristics lie between those of linseed and soybean oils. One of its main advantages for paint and varnishes is its extremely low after-yellowing due to its very low linolenic acid content. 

Early attempts at description of the changes in lipid composition included a diminished degree of unsaturation in deficient animals, indicated by a decrease of the iodine value of tissue lipids. When alkaline isomerization technique became available for measurement of polyenoic acids, the deficient animal was found to have a diminished content of dienoic acid and tetraenoic acid but an enhanced content of trienoic acid (Rieckehoff et al., 1949). Through supplementation with single fatty acids, it was discovered that 1in-oleic acid induced increases in tetraenoic acid (arachidonic acid) but that linolenic acid induced increases in pentaene and hexaene acids (Widmer Holman, 1950). These experiments prompted more elegant ones in the laboratories of Mead and Klenk in which the metabolism of linoleic acid to arachidonic acid, linolenic acid to penta-enoic and hexaenoic acids, and oleic to eicosatrienoic acid were described in detail (Mead, 1971). 

Plant oil Iodine value (mg per lOOg) Double bonds Palmitic Fatty acids (%) Stearic Oleic Unolek Linolenic... 

In another frying trial by Xu et al. (1999), three HOLL canola oils with different levels of linolenic acid and HOSO were compared with commercial PO. The oils were heated over a period of 80 h at 190°C by frying potato chips. Fatty acid analysis, iodine value, colour index, dielectric constant, free fatty acids and the total polar compounds were used for the assessment of the suitability of the oils. Additionally, a sensory evaluation was carried out... 

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