Linolenic acid vegetable oils

Rapeseed methyl ester (RME) is another alternative biofuel that can be used in diesel engines. RME has the advantages that it is renewable compared to diesel, non-toxic and less flammable compared with many other fuels, like ethanol. RME has the same cetane number, viscosity and density as diesel, contains no aromatic compounds and is biologically degradable with minor contamination in soil. RME can be produced from vegetable oils, but is mostly produced from rapeseed oil by pressing of the seeds or by extraction. Up to 3 tons of rapeseed can be produced from one hectare. The fatty acids in rapeseed oil are mostly oleic acid, linoleic acid and linolenic acid. The oil is pressed from the plant and after some purification allowed to react with methanol in the presence of potassium hydroxide as a catalyst, to produce a methyl ester, see Figure 6.6. 

Table 8.10. Fatty acid composition (relative %) and oxidizability of commercial new generation high-oleic (HO), medium-oleic (MO) and low-linolenic (LL) vegetable oils...

Linoleic acid is found in soybean, safflower and com oil, nuts, seeds, and some vegetables. a-Linolenic acid is found in flaxseeds, walnuts, and their oils canola oil is also a good source of a-linolenic acid. Edible oils rich in monounsaturated fatty acids are stable, flavorful, and nutritious for humans and animals. Oleic acid-rich soybean oil is more resistant to degradation by heat and oxidation and requires little... 

Rats fed a purified nonlipid diet containing vitamins A and D exhibit a reduced growth rate and reproductive deficiency which may be cured by the addition of linoleic, a-linolenic, and arachidonic acids to the diet. These fatty acids are found in high concentrations in vegetable oils (Table 14-2) and in small amounts in animal carcasses. These essential fatty acids are required for prostaglandin, thromboxane, leukotriene, and lipoxin formation (see below), and they also have various other functions which are less well defined. Essential fatty acids are found in the stmctural lipids of the cell, often in the 2 position of phospholipids, and are concerned with the structural integrity of the mitochondrial membrane. 

Dietary intake is of great importance. Linoleic acid (C18 2o)6) and a-linolenic acid (C18 3o)3) are the parent essential fatty acids for humans. Both fatty acids derive from vegetable oils. Higher fatty acids are then produced by chain elongation and desaturation. In addition, some of the prime essential fatty acids, AA (C20 4o)6), EPA (C20 5w3) and DHA (C22 6w3), can be obtained directly from the diet. Meat and eggs are rich in AA, whereas fish is a rich source of EPA and DHA [14]. 

LINOLENIC ACID, CAS 463-40-11. Also called 9.12,15-ocladecatri-enoie acid, formula CH,CH CH CHCH2CH rHrH CH CH(CH bCOOH. This is a polyunsaturated fatty ucid (three double bondsl, It occurs as the glyceride in many seetl tats. It ts an essential laity acid in the diet. See also Vegetable Oils (Edible). At room temperature, linolenic aeid is a colorless liquid soluble in most organic solvents insoluble in water. Specific gravity (1.916 (2(1/4"C mp -ll C bp 23()"C. Combustible. Linolenic acid finds use in various pharmaceuticals and drying oils. 

The major properties of nine of the principal edible vegetable oils are summarized in Tbble 2. For descriptions of the constituent acids, see also Arachidic Acid Capric Acid Caproic Acid Lauric Acid Linoleic Acid Linolenic Acid Myristic Acid Oleic Acid Palmitic Acid and Stearic Acid and Stearates. 

Mantzioris, E., James, M.J., Gibson, R.A., and Cleland, L.G. 1994. Dietary substitution with an alpha-linolenic acid-rich vegetable oil increases eicosapentaenoic acid concentrations in tissues. Am. J. Clin. Nutr. 59, 1304-1309. 

Reaction temperature and time were significant operating parameters, which are closely related to the energy costs, of the biodiesel production process. Figure 7 shows the effect of reaction time on the transesterification of rapeseed oil at a catalyst concentration of 1%, molar ratio of 1 6, and 60°C. Within 5 min, the reaction was rapid. Rapeseed oil was converted to above 85% within 5 min and reached equilibrium state after about 10 min. Several researchers reported that the conversion of vegetable oils to FAME was achieved above 80% within 5 min with a sufficient molar ratio (8,11). For a reaction time of 60 min, linoleic acid methyl ester was produced at a low conversion rate, whereas oleic and linolenic methyl ester were rapidly produced. 

The vegetable oil used was rapeseed oil (Nacalai Tesque Kyoto, Japan) without further treatment. The fatty acid content of the rapeseed oil mainly consisted of unsaturated fatty acids (93 wt%), with the saturated fatty acids of palmitic and stearic acids accounting for only a small amount (7 wt%). Various fatty acids of oleic (C181), linoleic (C18 2), linolenic (C18 3), and palmitic (C16 0) acids as well as their methyl esters were purchased from Nacalai Tesque. Anhydrous methanol and distilled water were also supplied by the same company. 

Rapeseed oil and its fatty acids (stearic, palmitic, oleic, linoleic, and linolenic acids) were chosen as the samples of vegetable oil. The experiments were performed in the batch- and flow-type supercritical biomass conversion systems developed in our laboratory. For the batch-type system, a reaction vessel was made of Inconel-625 with a volume of 5 mL for the flow-type system, the supercritical treatment tube was constructed from Hastelloy stainless steel (HC 276) with length of 84 m and an id of 1.2 mm, with the total volume being about 95 mL. Detailed information about the equipment can be found elsewhere (13). 

Extracted from the bean and often called Soyabean oil. A versatile carrier suitable for all skin types. It is comparatively high, up to 17%, in unsaturated fatty acids with the unsaturated linoleic (54%), oleic (24%), palmitic (10%), linolenic (7%) and stearic (4%). It also contains the highest amount of lecithin of any vegetable oil and the cold pressed oil is particularly high in vitamin E. It needs careful storage as it oxidizes easily. Soya oil may cause allergic reactions and has been reported to damage hair. 

The long-term health effects of eating partially hydrogenated vegetable oils concern some nutritionists because many unnatural fatty acids are produced. Consider the partial hydrogenation of linolenic acid by the addition of one or two equivalents of hydrogen. Show how this partial hydrogenation can produce at least three different fatty acids we have not seen before. 

Polyunsaturated fatty acids in vegetable oils, particulady linolenic esters in soybean oil, are especially sensitive to oxidation. Even a slight degree of oxidation, commonly referred to as flavor reversion, results in undesirable flavors, eg, beany, grassy, painty, or fishy. Oxidation is controlled by the exclusion of metal contaminants, eg, iron and copper addition of metal inactivators such as citric acid TniniTniiTn exposure to air, protection from light, and selective hydrogenation to decrease the linolenate content to ca 3% (74). Careful quality control is essential for the production of acceptable edible soybean oil products (75). 

Different varieties of flax Linum usitatissimum) are grown for fiber and for oil. Linseed oil is well known as one of the most unsaturated vegetable oils, resulting from its high level of linolenic acid (50-60%, Table 4). As a consequence of this, it oxidizes and polymerizes very readily and is used in paints, varnishes, and inks, in the production of linoleum, and as a sealant for concrete. These uses diminished with the appearance of alternative petroleum-based products, but the natural oil is coming back into favor on environmental grounds (33). 

Purslane (Portulaca oleracea). The plant (leaves, stem, and whole plant) is reported to be the richest vegetable source of n-3 acids, including low levels of the 20 5, 22 5, and 22 6 members. This is such a surprising result that it should be conhrmed. These acids have not been identihed in the seed oil, which contains palmitic (15%), stearic (4%), oleic (18%), linoleic (33%), and linolenic acids (26%) (165). 

The development of a characteristic, objectionable, beany, grassy, and hay-like flavor in soybean oil, commonly known as reversion flavor, is a classic problem of the food industry. Soybean oil tends to develop this objectionable flavor when its peroxide value is still as low as a few meq/kg, whereas other vegetable oils, such as cottonseed, com, and sunflower, do not (15, 51). Smouse and Chang (52) identified 71 compounds in the volatiles of a typical reverted-but-not-rancid soybean oil. They reported that 2-pentylfuran formed from the autoxidation of linoleic acid, which is the major fatty acid of soybean oil, and contributes significantly to the beany and grassy flavor of soybean oil. Other compounds identified in the reverted soybean oil also have fatty acids as their precursors. For example, the green bean flavor is caused by c/i-3-hexenal, which is formed by the autoxidation of linolenic acid that usually constitutes 2-11% in soybean oil. Linoleic acid oxidized to l-octen-3-ol, which is characterized by its mushroom-like flavor (53). 

Canola Oil Canola oil is obtained from low erucic acid, low glucosinolate rapeseed. The unique polyunsaturated fatty acid and low saturated composition of canola oil differentiates it from other oils. It has a higher oleic acid (18 1) content (55%) and lower linoleic acid (18 2) content (26%) than most other vegetable oils, but it contains 8-12% of linolenic acid (18 3) (58). Canola oil is most widely used in Canada and is considered a nutritionally balanced oil because of its favorable ratio of near 2 1 for linoleic to linolenic acid content. Unlike most other edible oils, the major breakdown products of canola oil are the cis, trans- and tram, trans-2,4-heptadienals with an odor character generally described as oily, fatty, and putty. Stored canola oil shows a sharp increase in the content of its degradation products, which are well above their odor detection thresholds. The aroma is dominated by cis, tram-, tram, frani-2,4-heptadienals, hexanal, nonanal, and the cis, trans- and... 

Standard canola oil is high in CIS fatty acids, about 95%, which is higher than the other commodity vegetable oils. It is high in CIS In - 9 oleic acid at about 60%, much higher than any other vegetable oils, and it is relatively low in polyunsaturated fatty acids, linoleic at about 21%, and linolenic at about 10%. Viscosity, cold hlter plugging point, and cetane number are some of the most important biodiesel fuel properties influenced by fatty acid composition. 

Cottonseed Oil Fatty Acid Composition. The specific fatty acid profile of the triglycerides in cottonseed is dependent on the variety of cotton grown, growing conditions such as temperature and rainfall, and the analytical method used to determine the profile. Table 5 summarizes the fatty acid composition observations of several research and commercial groups. Cottonseed oil is typical of the oleic-linoleic group of vegetable oils, because those two fatty acids comprise almost 75% of the total fatty acids. Although oleic acid makes up 22% and linoleic makes up 52%, less than 1 % linolenic acid is present. Palmitic fatty acid makes up about 24% of the fatty acids. Minor amounts of other saturated fatty acids are also found. 

Some physicochemical properties of conventional flaxseed oil and low linolenic varieties are presented in Table 1. The higher specific gravity of 0.935 observed for flaxseed oil than other vegetable oils can be directly attributed to the high contribution of linolenic acid. It is in line with the specific density of fatty acids that increases from 0.895 to 0.9038 and to 0.914 for oleic, linoleic, and linolenic acids, respectively (7). 

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