Oilseeds Oleic acid

For example, the LIFDI mass spectrum of biodiesel from oilseed rape revealed methyl esters of long-chain fatty acids as typical plant lipid constituents (Figure 14.3). The most prominent signal originated from the methyl ester of oleic acid (Ci i, m/z 296.4), accounting to 42.6% of the TII, followed by the methyl esters of linoleic acid (Ciga,m/z 294.4,23.8%), linolenic acid (Cm-,m/z 292.4,4.4%), stearic acid (Ci8 o, m/z 298.5, 2.8%), palmitic acid (Ci6 0, m/z 270.4, 1.4%), and gondoic acid (C2o i,... 

Cool temperatures during the 10-25 days after flowering are the main cause for higher amounts of linolenic acid in flax oils (14). For the same reason, flaxseed grown in the Canadian prairies, northern latimde, produce oils with higher levels of polyunsaturated fatty acids and lower contributions of oleic acid and samrated fatty acids. This phenomenon was also observed for other oilseeds such as sunflower, canola, and soybean (7, 13, 14). Similarly, a wide variation in fatty acid composition in Australian flaxseed samples was observed 13-25% of 18 1 and 46-64% of 18 3 (6). 

As previously mentioned, the triglycerides found in biomass are esters of the triol, glycerol, and fatty acids (Fig. 3.6). These water-insoluble, oil-soluble esters are common in many biomass species, especially the oilseed crops, but the concentrations are small compared to those of the polysaccharides and lignins. Many saturated fatty acids have been identified as constituents of the lipids. Surprisingly, almost all the fatty acids that have been found in natural lipids are straight-chain acids containing an even number of carbon atoms. Most lipids in biomass are esters of two or three fatty acids, the most common of which are lauric (Cn), myristic (Cu), palmitic (Cia), oleic (Cis), and linoleic (Cis) acids. Palmitic acid is of widest occurrence and is the major constituent (35 to 45%) of the fatty acids of palm oil. Lauric acid is the most abundant fatty acid of palm-kemel oil (52%), coconut oil (48%), and babassu nut oil (46%). The monounsaturated oleic acid and polyunsaturated linoleic acid comprise about 90% of sunflower oil fatty acids. Linoleic acid is the dominant fatty acid in com oil (55%), soybean oil (53%), and safflower oil (75%). Saturated fatty acids of 18 or more carbon atoms are widely distributed, but are usually present in biomass only in trace amounts, except in waxes. 

In the 1990s, the United Soybean Boards Better Bean Initiative proposed that a high-oleic acid soybean be developed. However, they subsequendy recommended that a mid-oleic acid /low linolenic acid soybean oil be developed as a new commodity oilseed. 

DuPont scientists were the first to clone FAD2 and FADS genes from the soybean (2). They also provided conclusive evidence for the mechanism of polyunsaturated fatty acid biosynthesis, when antisense or cosuppression of the FAD2 gene led to lower n-6 desaturase activity, and the accumulation of oleic acid in glycerolipids. This was demonstrated not only in soybeans, but also in other oilseed crops, such as canola and sunflower (Table 1). These transgenic events... 

It is probable that our ancestors of several million years ago developed the characteristics leading to our modem biochemistry by eating animal fats (Crawford and Marsh, 1989 Sinclair and O Dea, 1990 O Dea, 1991). At first glance this should simplify discussion of animal fats, as shown by the basic fatty acids of Table 10.1. A popular shorthand notation is used to indicate the stmctures of common fatty acids. In the format x yn-z, x is the chain length or number of carbons in the chain, y is the number of methylene-interrupted cis ethylenic bonds and z is the inclusive number of carbon atoms from the terminal methyl group to the center of the nearest bond. As few as six fatty acids appear to adequately describe animal depot fats. Those fats listed are dominated by two fatty acids, 16 0 (palmitic) and 18 1 (oleic) add. Although tropical seed oils may be rich in C12-C18 saturated fatty adds (Elson, 1992), temperate oilseeds are rich in oleic acid and tend to include quantities of two fatty acids more unsaturated than oleic, especially 18 2n-6 (linoleic), and sometimes 18 3n-3 (linolenic). Even the original rapeseed (Brassica sp.) oil, with up to 50% of 22 ln-9 (emdc) acid usually had approximately 20% 18 2/1-6 and 10% 18 3/i-3 adds (Ackman 1983, 1990). 

Whole sunflower seeds contain about 40% oil and 25% protein. Small black sunflower seeds may contain up to 55% oil. In the 1980s sunflower became a major oilseed crop after the introduction of high yielding varieties. Linoleic (66-72%) and oleic acids (16-20%) are the major fatty acids in oil extracted from regular sunflower oil seeds. Saturated fatty acids, mainly palmitic and stearic acids, comprise less than 15% of the total fatty acids in the oil. 

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