Fatty acids in olive oil

The application of 13C NMR for the rapid analysis of the oil composition of oil seeds is well known [16], 13C NMR has recently been applied to the quantitative analysis of the most abundant fatty acids in olive oil [17]. The values obtained by this method differed by only up to 5% compared with GLC analysis. The quantitative analysis was applied to the olefmic region of the high resolution 13C NMR spectrum of virgin olive oil to detect adulteration by other oils which differed significantly in their fatty acid composition. The application of the methodology for the detection of adulteration of olive oil by hazelnut oil is more challenging as both oils have similar chemical profiles and further experiments are in progress. 

The common fatty acids have a linear chain containing an even number of carbon atoms, which reflects that the fatty acid chain is built up two carbon atoms at a time during biosynthesis. The structures and common names for several common fatty acids are provided in table 18.1. Fatty acids such as palmitic and stearic acids contain only carbon-carbon single bonds and are termed saturated. Other fatty acids such as oleic acid contain a single carbon-carbon double bond and are termed monounsaturated. Note that the geometry around this bond is cis, not trans. Oleic acid is found in high concentration in olive oil, which is low in saturated fatty acids. In fact, about 83% of all fatty acids in olive oil is oleic acid. Another 7% is linoleic acid. The remainder, only 10%, is saturated fatty acids. Butter, in contrast, contains about 25% oleic acid and more than 35% saturated fatty acids. 

Palmitic acid (C16 saturated) is the most common fatty acid in living things. Oleic acid (C g mono-unsaturated) is the major fatty acid in olive oil. Arachidonic acid (C20 tctra-unsaturated) is a rare fatty acid, which is the precursor of the very important prostaglandins, thromboxanes, and leukotrienes, of which more later. 

Scano R et al. (1999) Recognition and quantitation of c/s-vaccenic and eicosenoic fatty acids in olive oils by C-13-nuclear magnetic resonance spectroscopy. Lipids, 34, 757-759. 

Major analytical practices are given in brief. Palmitic acid (C16 0) is the principal saturated fatty acid in olive oil, responsible for its figeabihty at low temperamre. 

Unsaturated fats, found in plants, are better choices for a healthful diet. These fats, usually soft or liquid at room temperature, vary from mono-unsaturated (the major fatty acid in olive oil) to polyunsaturated fatty acids (found in cottonseed, soybean, corn, and canola oils). Hydrogenation, a process that changes fatty acids from liquid to solid, creates trans fats. Trans fats raise blood cholesterol levels and may contribute to heart disease. 

Large supply of naturally derived lipids can be obtained from plants in which many oils and fatty acids can be readily extracted and purified. Animal sources (e.g., eggs or milkfats) are used to derive complex lipids such as phospholipids and cholesterol. Yield from natural sources is dependent on the weight-percent composition and the efficiency of the extraction procedure. The constitution of fatty acids in vegetable oils varies widely from different sources. For example, oleic acid is present at 64.6% by weight in olive oil but is present at only 0.7% in palm kernel oil. Similarly, castor oil triglyceride is comprised of almost entirely ricinoleic chains. There are numerous raw material suppliers of oils and oil fractions worldwide. As such, the relative cost of bulk purified... 

The uses cited by Coleman and Macrae (1980) for the lipase catalysed reaction are examples of acidolysis and transesterification. Acidolysis is illustrated by the increase in l(3)-palmitoyl-3(l)-stearoyl-2-olein (POSt) resulting from the reaction of palm oil mid-fraction with stearic acid in the presence of a 1,3-specific enzyme, and by the increase in the content of linoleic acid in olive oil when that oil is reacted with linoleic acid in the presence of an enzyme with fatty acid specificity. An example of transesterification is shown by the increase in POSt triglycerides when a 1,3-specific enzyme is used to catalyse the interesterification of shea butter and palm oil mid-fraction. 

The Mediterranean diet, rich in fresh fruits and vegetables, was shown to be inversely related to the incidence of eardiovaseular disease, as shown in the Seven Countries Studies [59,169-171]. OUve oil, the dietary fat of choice in the Mediterranean area, in eomparison to other vegetable oils has a peculiar fatty acid composition. The monounsaturated oleic acid (C-18 l, n = 9) is the most abundant fatty acid in oUve oil (56-84%), whereas the polyunsaturated Unoleic acid (C-18 2, n = 6) ranges only from 3% to 21%. In addition, oUve oil eontains a variety of minor components, including polyphenols (up to 800 mg/kg), whieh provide the typical taste and aroma of extra virgin olive oil and eonfer on this oil its stability to oxidation [172]. 

GC-MS coupled with chemometric techniques has been used to characterize roasted coffees [54], to detect adulterants in olive oils [55], and to determine fatty acids in fish oils [56], GC-MS data have also been used in toxicology assessments to reveal patterns in complex chemical mixtures with the help of multivariate analyses [57,58],... 

Two distinctly different types of oils are produced from the fruit of the Southeast Asia and African oil palm, Elaeis guineensis, and its hybrids with the South and Central American palm E. oleifera. Palm oil is otained from the fleshy part of the fruit, which resembles an oversized olive about the size of a small chicken egg. Palm kernel oil is derived from the kernel within the nut. Well over 98 percent of the fatty acids in palm oil belong to the C 16 and C 18 group, whereas approximately 64 percent of the fatty acids in palm kernel oil consist of the C 12 and C 14 lauric group. 

Much of the fat taken in via the diet will contain unsaturated fatty acids, particularly that portion which originates from plant material. For example, the fats in olive oil contain up to 85% oleic acid... 

Monounsaturated fats Triacylglycerols containing primarily fatty acids with one double bond are referred to as monounsaturated fat. Unsaturated fatty acids are generally derived from vegetables and fish. When substituted for saturated fatty acids in the diet, monounsaturated fats lower both total plasma cholesterol and LDL cholesterol, but increase HDLs. This ability of monounsaturated fats to favorably modify lipoprotein levels may explain, in part, the observation that Mediterranean cultures, with diets rich in olive oil (high in monounsaturated oleic acid), show a low incidence of coronary heart disease. 

Italian EVOO from different cultivars and geographical areas of the Apulia region were investigated by Sacco et al. (2000), measuring analytical parameters (fatty acids in particular) and recording 1H NMR spectra of phenolic extracts of olive oil. Their metabolite content was confirmed to... 

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