**1. Introduction**

446 Olive Oil – Constituents, Quality, Health Properties and Bioconversions

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Functional properties of fats and oils do not depend only on their fatty acid composition but also on the distribution of these fatty acids in the three positions of the glycerol backbone. This gives the fat or oil its commercial value. (Zhao,2005) There is a growing demand for lipids with desired characteristics ,thus researches have given way to these demands by the development of structured lipids with triacylglycerols that have predetermined composition and distribution of fatty acids. Structured lipids are now considered as alternatives to conventional fats not on the basis of saturate/polyunsaturate ratios but rather on their impact on cholesterol deposition. With the advances in the biotechnology and chemistry of fats and oils it is now possible to design fats and oils with properties that are desired. Recent years have seen great interest in the biotechnological modification and synthesis of structured triacylglycerols. Modification of fats and oil triacylglycerols to improve functionality have been carried out with various oils including olive oil. Olive oil enjoys a privileged position amongst edible oils and is still a buoyant commerce because of the large consumption of Mediterranean inhabitants (Oh et al,2009). It is one of the most expensive vegetable oils and of all the vegetable oils, olive oil is the best source of the monounsaturated fatty acid, oleic acid (72-83%)Risk factors for cardiovascular disease such as the level of homocysteine and total and low density lipoprotein (LDL) cholesterol in plasma have been reported to be reduced by oleic acid (Baro et al,2003). Olive oil is more than just oleic acid and because of its properties and qualities, it is used almost entirely in dietary consumption and even new markets have been created for this oil.

#### **2. Triacyglycerol structure and characteristics**

Triacylglycerols are by far the most abundant single lipid class and virtually all important fats and oils of plant or fat origin and most animal depot fats consist almost entirely of this lipid.

#### **2.1 Triacylglycerol structure**

Glycerol is a trihydric alcohol (containing three **-OH** hydroxyl groups) that can combine with up to three fatty acids to form monoacylglycerols, diacylglycerols, and triacylglycerols.

Biocatalyzed Production of Structured Olive Oil Triacylglycerols 449

**Triacylglycerol (TG)specie % of Total TG (Range)** 

**LLL** 0 - 0.8 **OLL** 0.3 - 5.8 **OLLn** 0.9 – 0.6 **OOLn** 1.0 – 1.5 **PLL** 0.5 – 2.8 **POLn** 0.3 - 1.1 **OOL** 10.4 - 18.2 **PoOO** 0 - 1.1 **POL** 4.5 - 12.3 **PPoO** 0.4 - 1.2 **PPL** 0.7 - 2.1 **OOO** 21.8– 43.1 **POO** 20 - 23.1 **PPO** 2.9 - 5.3 **PSPo** 0 - 0.8 **PPP** 0 - 0.5 **SOO** 3.6 - 3.7 **PSO** 0.4 - 1.2 **PPS** 0 - 0.6

Table 1. Triacylglycerol Composition as Analyzed by HPLC

**2.3 Fatty acid profile and distribution intriacylglycerols** 

The fatty acid composition of olive oil varies widely depending on the cultivar, maturity of the fruit, altitude, climate, and several other factors(Galtier et al,2008). The major fatty acids in olive oil triacylglycerols are oleic acid (C18:1), a monounsaturated omega-9 fatty acid which makes up 55 to 83% of olive oil. Another fatty acid is linoleic acid (C18:2), a polyunsaturated omega-6 fatty acid that makes up about 3.5 to 21% of olive oil. Palmitic Acid (C16:0), a saturated fatty acid that makes up 7.5 to 20% of olive oil, stearic Acid (C18:0), a saturated fatty acid that makes up 0.5 to 5% of olive oil and linolenic acid (C18:3) (specifically alpha-Linolenic Acid), a polyunsaturated omega-3 fatty acid that makes up 0 to 1.5% of olive oil .Olive oil contains more oleic acid and less linoleic and linolenic acids than other vegetable oils, that is, more monounsaturated than polyunsaturated fatty acids . This renders olive oil more resistant to oxidation. The different fatty acids have stereospecific distribution on the glycerol backbone rather than a completely random or "restricted random" distribution. In most vegetable oils either 18:1 or 18:2 are exclusively at the sn-2 position in the triacylglycerol species like OOO,LLL,POL and LLO. Linolenic acid (C18:3) occurs less commonly,but when present , is at the sn-3 position as seen for OOLn in canola oil. Oleic acid is commonly at the sn-2 position of the olive oil triacylglycerols. (Karupiah & Sundram, 2007).Table 2 shows the fatty acid distribution in the three positions

Fatty acids may combine with any of the three hydroxyl groups to create a wide diversity of compounds. A triacylglycerol (TAG)(Fig.1 ) consists of three fatty acids(R) to one glycerol molecule.

Fig. 1. Stucture of a triacylglycerol

If all three fatty acids are identical,it is a simple triacylglycerol. The more common forms however are the "mixed" triacylglycerols in which two or three kinds of fatty acids are present in the molecule. The positions occupied by these fatty acids are numbered relative to their stereospecificity or stereospecific numbering (sn) as sn-1,sn-2 and sn-3.The orientation of the triacylglycerol structure specificity is as follows: if the fatty acid esterified to the middle carbon of the glycerol backbone is considered to the left ( on the plane of the page) , then the top carbon is sn-1,the bottom carbon is numbered sn-3 (below or behind the plane of the page) and the middle carbon is subsequently numbered as sn-2. The fatty acids in the triacylglycerol define the characteristics and properties of the triacylglycerol molecule. Both the physical and chemical characteristics of fats are influenced greatly by the kinds and proportions of the component fatty acids and the way in which these are positioned in the glycerol molecule (Breckenridge, W.C. 1978; Christie, W.W.1982; Karupiah, T. & Sundram, K.2007).

#### **2.2 Triacylglycerol species of olive oil**

The triacylglycerol composition is a relevant information for the restructuring of lipids. Most often this defines the properties being sought to make them more suitable for their end use. These are mainly nutritional or physical. Nutritional properties are important in structured lipids as there is a growing appreciation for this information because metabolism is intimately linked to triacylglycerol composition. Triacylglycerol composition by HPLC of olive oil as reported in literature is given in Table 1(Christie,1982;Uzzan,1996;Aranda et al,2004). Most prevalent triacylglycerols in olive oil is the oleic-oleic-oleic (OOO) triacylglycerol, followed, in order of incidence, by palmitic-oleic-oleic (POO), then oleicoleic-linoleic (OOL), then palmitic-oleic-linoleic (POL), then by stearic-oleic-oleic (SOO).The triacylglycerol species show a small degree of asymmetry in the distribution of fatty acids among the three positions of the glycerol moiety.

However, a single symmetric triacylglycerol specie (OOO) represents almost half of the total triacylglycerols. New developments in analytical methodology have allowed the evaluation of the degree of asymmetry in other fractions. The information on the individual triacylglycerols would be very useful in the structured lipid production.

Fatty acids may combine with any of the three hydroxyl groups to create a wide diversity of compounds. A triacylglycerol (TAG)(Fig.1 ) consists of three fatty acids(R) to one glycerol

If all three fatty acids are identical,it is a simple triacylglycerol. The more common forms however are the "mixed" triacylglycerols in which two or three kinds of fatty acids are present in the molecule. The positions occupied by these fatty acids are numbered relative to their stereospecificity or stereospecific numbering (sn) as sn-1,sn-2 and sn-3.The orientation of the triacylglycerol structure specificity is as follows: if the fatty acid esterified to the middle carbon of the glycerol backbone is considered to the left ( on the plane of the page) , then the top carbon is sn-1,the bottom carbon is numbered sn-3 (below or behind the plane of the page) and the middle carbon is subsequently numbered as sn-2. The fatty acids in the triacylglycerol define the characteristics and properties of the triacylglycerol molecule. Both the physical and chemical characteristics of fats are influenced greatly by the kinds and proportions of the component fatty acids and the way in which these are positioned in the glycerol molecule (Breckenridge, W.C. 1978; Christie, W.W.1982; Karupiah, T. &

The triacylglycerol composition is a relevant information for the restructuring of lipids. Most often this defines the properties being sought to make them more suitable for their end use. These are mainly nutritional or physical. Nutritional properties are important in structured lipids as there is a growing appreciation for this information because metabolism is intimately linked to triacylglycerol composition. Triacylglycerol composition by HPLC of olive oil as reported in literature is given in Table 1(Christie,1982;Uzzan,1996;Aranda et al,2004). Most prevalent triacylglycerols in olive oil is the oleic-oleic-oleic (OOO) triacylglycerol, followed, in order of incidence, by palmitic-oleic-oleic (POO), then oleicoleic-linoleic (OOL), then palmitic-oleic-linoleic (POL), then by stearic-oleic-oleic (SOO).The triacylglycerol species show a small degree of asymmetry in the distribution of fatty acids

However, a single symmetric triacylglycerol specie (OOO) represents almost half of the total triacylglycerols. New developments in analytical methodology have allowed the evaluation of the degree of asymmetry in other fractions. The information on the individual

triacylglycerols would be very useful in the structured lipid production.

molecule.

Fig. 1. Stucture of a triacylglycerol

Sundram, K.2007).

**2.2 Triacylglycerol species of olive oil** 

among the three positions of the glycerol moiety.


Table 1. Triacylglycerol Composition as Analyzed by HPLC
