Linoleic acid coffee

Coffee oil contains about 47% linoleic, 8% oleic, 1% hexa-decenoic, 32% palmitic, 8% stearic, and 5% behenic and longer chain fatty acids (64). As linoleic acid is the major unsaturated fatty acid in coffee oil, its major oxidation products 2,4-alkadienals and hexen-1,6-dial would play a major role in... 

It is a well-known product of autoxidation of linoleic acid (Ci8 2), but it is not a flavor substance (Ullrich and Grosch, 1987). As the other volatile alkanes, it can eventually be present as a residual trace of solvent after a petroleum ether extraction of ground coffee samples. 

The lipid fraction appears to be very stable and survives the roasting process with only minor changes. Its composition is given in Table 21.5. Linoleic acid is the predominant fatty acid, followed by palmitic acid. The raw coffee waxes, together with hydroxytiyptamide esters of various fatty acids (arachidic, behenic and ligno-ceric) originate from the fruit epicarp. These compounds are 0.06-0.1% of normally roasted coffee. The diterpenes present are cafestol (I, R = H), 16-0-methylcafestol (I, R = CH3), and kah-... 

This aldehyde is a product of autoxidation of linolenic acid (Grosch, 1998a), not linoleic as quoted in the publication by Full et al., which is present in green coffee, representing 1.1 1.5% of the total acid content of immature or mature beans (Guyot et al., 1988a). 

An insight into the factors that enhance lipid oxidation will help one understand why some food products develop oxidized off-flavors very rapidly. A primary consideration is the number and type of double bonds in a fatty acid. The relative rates of oxidation for arachidonic, linolenic, linoleic, and oleic acid are 40 20 10 1. In some food applications, the highly unsaturated fatty acids, e.g., linolenic acid, must be selectively hydrogenated in order to permit an acceptable shelf life. For example, the presence of any linolenic acid in a dry coffee whitener would limit shelf life to less than three months. 

Coffee oil contains mainly glycerides of fatty acids (e.g., linoleic, palmitic, oleic, and stearic acids, with the first two in predominant concentrations) and 5-8% of unsaponifiable matter, which consists of squalene, n-nonaco-sane, lanosterol, cafestol, cahweol, sitosterol, stigmasterol, methylsterols, tocopherols (a, 3,... 

Coffee is an acidic beverage [20]. The pH of percolated coffee is about 4.9-5.0. Coffee is known to contain acids [21,22,25], mainly chlorogenic acids [23-24] (Fig. 14.4), and smaller amounts of nicotinic and citric acids. Linoleic, oleic, palmitic, and stearic acids are present as glycerides. These acids are colorless and cannot stain fibers. However, they can contribute indirectly to the formation of colored species when coffee beans are roasted. 

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