Vegetable oils common fatty acids

Historically, antifoaming agents or, more commonly, defoamers were single component liquid systems or homogeneous solutions derived from vegetable oils and fatty acids. Other useful materials included mineral oils, aliphatic and aromatic hydrocarbons [16,17]. 

Triacylglycerols I (cf. Fig. 1) of traditional oil seed crops contain a limited number of different fatty acids eight of these common fatty acids contribute more than 97% of the world production of edible vegetable oils [5]. Fatty acids such as palmitic and stearic acids are formed by fatty acid synthase in the plastids of plant cells. 

Figure 2. Methyl esters of common fatty acids found in vegetable oils...

Table 1. Common fatty acids in vegetable oil and animal fat triglycerides [2,3]...

Monounsaturated fatty acids. The report that monounsaturated fatty acids (viz., oleic acid) were just as effective as polyunsaturated fatty acids (viz., linoleic acid) in lowering plasma total and low-density lipoprotein (LDL) cholesterol (100) aroused interest in the nutritional properties of canola oil. Canola oil contains 60% oleic acid and is second only to olive oil, among the common vegetable oils, in oleic acid content. Although avocado oil and high-oleic sunflower oil also contain high levels of oleic acid (>70%), they are minor constituents in the average diet. 

An active catalyst for hydrogenating the lauryl ester of coconut oil fatty acid is made by decomposing copper-ammonium chromate at 350-400°C. A 90 per cent hydrogenation is. obtained in 2 hr by operating at 275°C and 3,000 lb hydrogen pressure." Coconut oil is one of the vegetable oils commonly hydrogenated to produce alcohols. In this case, the result-... 

HEAR and LEAR oils contain brassicasterol, a C28 sterol (Fig. 3) characteristic of Brassica oils. It does not occur in other common edible vegetable oils (Table XII) except for mustard oil. Brassicasterol is, thus, a key factor in identifying Brassica oils either by themselves or after blending with other edible oils, since fatty acid compositions cover a range for each oil due to cultivar, climate, or maturity, and overlaps in physical properties are common (Spencer et al., 1976). Among recent authors examining this question... 

The magnitude of the variation in the composition of rapeseed oil and meal now commercially available has created a need for new terms to describe the products derived from rapeseed. The fatty acid composition of most edible vegetable oils such as soybean, sunflower, or cottonseed oils, varies within narrow limits. Thus, the species or commodity name (e.g., soybean oil) provides a reasonable description of the fatty add composition of soybean oil. In contrast, the erucic acid content of commercially available rapeseed oil may vary from near zero to 55%, and the oleic acid from 10 to more than 60%. A number of terms have been proposed or utilized to describe the new rapeseed oil whose fatty acid composition has been altered by the elimination of erucic acid these include low erucic acid rape-seed oil (LEAR), canbra, and canola. Similar terms such as high erucic acid rapeseed oil (HEAR) and common or traditional rapeseed oil have been used to describe rapeseed oil whose fatty acid composition includes substantial amounts of erucic acid. 

The fatty polyamides are produced by reacting di- and polyfunctional amines with polybasic acids that result from condensations of unsaturated vegetable oil acids. The most commonly used amines are ethylene diamine and diethylene triamine. The dicarboxylic acids are synthesized by heating mixtures of unsaturated vegetable fatty acids. The starting materials may come from linseed, soybean, or tung (also called China wood) oil. The fatty acids are heated for several hours at 300°C. If a catalyst is used, the heating is done at a lower temperature. After condensation, the volatile fractions are removed by vacuum. The residues, called dimer acids, are then condensed with the amines. A formation of one such dimer acid from linoleic acid can be illustrated as follows ... 

Vegetable oils comprise a mixture of triglycerides (albeit with one or two specific structures which usually predominate). These compositions vary according to plant species, crop type, season, and growing conditions [4]. Table 1.2 enumerates the most common fatty acids in the triglycerides of plant oils and Scheme 1.2 shows their structures. 

You are to synthesize the ethyl ester of lauric add in Experiment [8A]. Laurie acid, CH3(CH2)ioC02H (dodecanoic acid), is one of the four most common fatty acids found in naturally occurring triglycerides. It is named for the laurel botanical family from which it was first isolated in 1842. It is the most abundant of the fatty acids isolated from the vegetable oils of palm kernel oil (52%), the seed fat of Elaeis guineensis of coconut oil (48%), Cocos nucifera and of babassu oil (A6%), Attalea funifera. 

FIGURE 13.3 Structural formula of a typical vegetable oil containing three of the most common fatty acids (oleic, linoleic, and linolenic) in canola oil, which is extracted from seeds of the rape plant (Brassica napus). 

Animal fats and vegetable oils mostly contain unsaturated straight chain fatty adds with 10 36 carbon atoms. The most common fatty acids are monoenoic and polyenoic fatty acids with 16-18 carbon atoms. The unsaturated fatty acids content of fats and oils ranges widely, from more than 90% of total fatty acids in rapeseed oil to less than 10% in coconut oil. Unsaturated fatty acids in animal fats occur in a much smaller concentration range, usually between 50 and 70% (Table 3.7). The only exception is fish oil, because it contains fatty acids with 20 22 carbon atoms and 4-6 double bonds (Table 3.12). The fat offreshwater fish differs in composition from the fatty adds in the fat of marine fish. Fish do not synthesise... 

Table 22.2 presents the fatty acid composition of the different vegetable oils commonly used in polymerization reactions [4-6]. Additionally, the fatty acid distribution of fish and algae oils are shown. As shown in the table, each oil has a specific fatty acid distribution. Oils from algae, such as microalgae, are raw materials with good perspectives for... 

Table 3.16 shows the most commercially useful vegetable oils with an indication of unsaturated or saturated acid content. Natural oils, or glycerides, contain a mixture of long-chain fatfy acids randomly esterified with glycerol. All natural fatty acids have an even nttmber of carbon atoms, usually Ci4-C2o.but predominantly Qe-Cig. As many as three double bonds are present in some common fatty acids, all in the cis form and never conjugated. 

Table 6.3 Common fatty acid found in vegetables oil...

Polyunsaturated fatty acids in vegetable oils, particularly finolenic 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 minimum exposure to air, protection from light, and selective hydrogenation to decrease the finolenate content to ca 3% (74). Careful quality control is essential for the production of acceptable edible soybean oil products (75). 

Although vegetable oils and animals fats were commonly used in ancient times, most higher acids were not known until the beginning of the nineteenth century. Then the nature of the naturally occurring 18-carbon fatty acids was estabHshed, and hundreds of long-chain fatty acids have been isolated from natural sources and characterized. 

In the characterization of alkyd resin formulations the palmitic acid to stearic acid (P/S) ratio, often used to identify the type of oil in a binder, cannot be applied as many different oils other than the traditional ones are commonly employed in industrial formulations. Moreover, they are often in mixtures, with the additional complication that fatty acids are also sometime added to the vegetable oils, thus making it impossible to rely on measured P/S values. In any case it is important to always derivatize the samples if Py-GC/MS is used and an alkyd is suspected. Phthalic anhydride will be detected also in an underivatized alkyd pyrogram however, isophthalic acid will not, leading to confusion and the possibility of uncorrected identification [92]. 

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