**3.1 Bioactive compounds**

Olive oil glyceridic fraction consists of triacylglycerols, diacylglycerols, monoacylglycerols and free fatty acids (FFA). Among them, 80% of them are unsaturated fatty acids. It is particularly rich in essential monounsaturated fatty acids (55–83% of oleic acid) and polyunsaturated fatty acids (2.5–21% of linoleic acid) [12]. The remaining fatty acids, apart from C16: 1, display an average value ranging from 0.3 to 3.5% (**Table 1** and **Figure 3**). Nevertheless, linolenic acid is a minority and its concentration is lower than 1% [12]. A low level of linolenic acid can be used to detect adulteration via some vegetable oils such as rapeseed and soybean oils [13]. Small quantities of saturated fatty acids also compose the triglycerides of olive oil: stearic acid (about 0.5–5%) and palmitic acid (about 7.5–20%). The remaining fatty acids (C17: 0, C17: 1, C20: 0, C20: 1, and C22: 0) are found to be of lower magnitudes. Since their concentrations are below 0.5% (**Table 1**). The unsaponified matter (about 1–2%) contains sterols, triterpene alcohols, tocopherol (mainly α-tocopherol), tocotrienol polyphenols, and squalene. The oil also contains a non-negligible proportion of volatile compounds. The total phytosterols content of VOO ranges between 100 and 200 mg/100 g. Also, 100 mg/100 g represents the inferior


*SFA-Saturated Fatty acids, MUFA-Monounsaturated fatty acids, PUFA-Polyunsaturated fatty acids: Apparent beta-sitosterol: beta-sitosterol +delta-5-avenasterol +delta-5-23-stigmastadienol +clerosterol + sitostanol +delta 5–24-stigmastadienol.*

#### **Table 1.**

*Physicochemical parameters, fatty acids, phytosterols, and tocopherols composition of olive oil.*

*Olive Oil: Extraction Technology, Chemical Composition, and Enrichment Using Natural… DOI: http://dx.doi.org/10.5772/intechopen.102701*

**Figure 3.** *Chromatogram of fatty acids.*

limit set by the international olive council [12]. Apparent beta-sitosterol, (beta-sitosterol + delta-5-avenasterol + delta-5-23-stigmastadienol + clerosterol + sitostanol + delta 5–24-stigmastadienol) are the main compounds in the sterol fraction with a value more than 93% while β-sitosterol has the greatest relative percentage [14, 15] (**Figure 4**). VOO content also includes up to 4.5 g/100 g of total phytosterols [12]. The erythrodiol (5α-olean-12-ene-3β, 28-diol, homo-olestranol) in free and esterified forms and are the major triterpene di-alcohols found in olive oil [14], and their percentage reached up to 4.5% of the total content of sterols [12]. Moreover, four isoforms of tocopherols (α, β, γ, and δ-tocopherol) (**Figure 5**) and four tocotrienols (α, β, γ and δ- Tocotrienol) are present in olive oil. α-tocopherol is the main tocopherol found in olive oil, constituting more than 90% of the total tocopherol fraction [14]. Cunha et al. [16] reported that the proportions of tocopherols and tocotrienols ranged from 100 to 270 mg/kg in Portuguese olive oils [16]. Gharby et al. [47] found that the values of tocopherols varied from 150 to 250 mg/kg in three varieties ('Arbequina', 'Moroccan Picholine', and 'Picual') of olive oil [17]. Moreover, another study, based on the comparison of the tocopherol contents of olive oils from 4 different varieties harvested at different ripening periods found

**Figure 4.** *Chromatogram of sterols.*


#### **Figure 5.**

*Tocopherols chemical structure.*

that the α-tocopherol (major tocopherol) in oils obtained from olives composed of 130.54–180.43 mg/kg [18]. In general, tocopherol and tocotrienol levels in oil fluctuate with several factors such as harvest year, climatic conditions, storage time, extraction method, soil properties and spacing between olive trees [19]. Tocopherols possess a strong antioxidant power [20]. Together with tocopherols and tocotrienols, olive oil contains other antioxidant molecules such as polyphenolic compounds.

Many research works have demonstrated that the content of tocopherols in VOO is lower than that of argan oil [21–23].

The phenolic compounds are endowed to have a large scale of biological functions including stability to auto-oxidation, beneficial effects on human health [24]. About their well-known activities, olive oil polyphenols have been proven to possess an effective role in maintaining the organoleptic properties and the stability of olive oils [25].

Such bioactive compounds are extensively studied for their anti-inflammatory, antioxidant, neuroprotective, cardioprotective, antidiabetic, antimicrobial, and anticancer properties [26–29].

Franco et al. reported that phenolic compounds have a considerable increase during olive fruit growth. However, they are reduced when the fruits reach the maturation stage [30]. Khalatbary documented that the total phenolic content (TPC) in olive oils varies from 190 to 500 mg/kg [31]. In addition, in extra virgin olive oil, TPC commonly varies from 250 to 925 mg/kg [32]. Other factors including climatic conditions, variety, storage time, extraction conditions, soil properties, and analysis of polyphenolic compounds can lead to important variations in TPC [33]. Likewise, several classes of polyphenols are found in olive oils. These are presented as a separate class, to better understand the antioxidant phenolic chemistry of olive oil [33]. Finicelli et al. classify olive oil polyphenols following their chemical structure as follows [34]:

*Olive Oil: Extraction Technology, Chemical Composition, and Enrichment Using Natural… DOI: http://dx.doi.org/10.5772/intechopen.102701*


The volatile fraction of VOOs has been reported to have about 280 different compounds [38]. The majority of volatile compounds are quickly developed during olive milling as a result of the disturbance of olive cells [39]. Although, Nardella et al. reported that most of the volatile compounds typical of olive oils are generated during

**Figure 6.** *Some phenolic alcohols present in olive oil.*

malaxation due to the activation of particular pathways, in which the lipoxygenase (LOX) enzyme plays an essential role in producing a large quantity of C6 aldehydes, esters, and alcohols. These constitute almost all of the positive sensory marks in olive oils [40]. Such changes are initiated when olive tissues are affected, thereby enhancing the liberation of endogenous enzymes like hydroperoxide lyase and lipoxygenase [40].

Besides, several analytical techniques have been used to determine volatiles composition in olive oil. The main important are: GC (gas chromatography), HPLC (high-performance liquid chromatography), HPLC/MS (high-performance liquid chromatography/mass spectroscopy), IRMS (isotope ratio mass spectroscopy), ICP (inductively coupled plasma spectroscopy), NMR (nuclear magnetic resonance), SPME-GC/MS (solid-phase microextraction followed by gas chromatography/mass spectrometry, SNIF/NMR (specific natural isotopic fractionation nuclear magnetic resonance), SCIRA (stable carbon isotope ratio analysis), PTR/MS (proton transfer mass spectrometry) [41]. Fregapane et al. reported that the composition of volatiles may be affected significantly according to many factors such as cropping season, olive variety, harvest time, technological parameters, and agronomic conditions among other factors [42]. Ghanbari et al. reported that several chemical factors such as hydrophobicity, volatility, position, and functional groups type are reported to be directly linked to the odor degree of a given volatile component more than its content [38]. Theodosi et al. investigated correlations between the composition of volatiles of olive oil and altitude variation. The findings demonstrate that the total volatile compounds of 'Koroneiki' olive oil samples and altitude levels are negatively associated. The most important volatile compounds are alcohols, aldehydes, esters, and hydrocarbons [43].
