Composition of extra virgin olive oil

Chemical Properties and Composition of Extra Virgin Olive Oil

It is well known that the characteristics and composition of olive oil depend on many factors: cultivar, pedo-climatic environment, cultivation system, time and method of olive harvest, technology and processing methods, and product storage. Olive oils differ in both organoleptic (aroma, smell, taste) and chemical characteristics (composition, acidity, etc.). Many of the factors that influence the quality of oil are unchangeable (for example, pedo-climatic conditions), as they are typical of a specific location, while others can be easily adaptable, such as cultivation techniques and extraction methods. Therefore, to produce excellent oil, it is necessary to identify and highlight the best organoleptic and chemical characteristics that are worthy of consumer attention. Olive oil is a fat that remains in a liquid state at room temperature (20°C) and is composed, from a chemical standpoint, of 98-99% of a mixture of triglycerides known as the saponifiable fraction, with the remaining 1-2% being a group of compounds referred to as unsaponifiable.

Saponifiable Fraction (Glycerides)

Triglycerides differ from each other based on the nature of the fatty acids and/or their position; the fatty acids, depending on the degree of saturation by hydrogen atoms, are classified into saturated and unsaturated fatty acids. Saturated fatty acids are those fats that appear with solid consistency in nature (common in animal fats), while unsaturated fats are naturally found with liquid consistency at room temperature and consist of monounsaturated and polyunsaturated fatty acids, which are categorized based on the presence of one or more double bonds (double bonds provide greater fluidity, lower melting points, and make the oil less stable as it can be easily attacked by oxygen). Analyzing the acidic composition of olive oil, it is evident that the monounsaturated fraction, represented by oleic acid, is the most abundant (up to 83%), while all others present much lower percentages; for example, saturated fatty acids such as palmitic and stearic acid are present in olive oil with values ranging from 5.7% to 18.6% and from 0.5% to 4.0% respectively.

Among the polyunsaturated fatty acids, linolenic and linoleic acid prevail in olive oil, generally referred to as “essential fatty acids” (EFA) because they are essential for the growth and functioning of tissues, and humans cannot synthesize them; their percentages range from 0.1% to 0.6% and from 3.5% to 20.0%. The high content of monounsaturated fatty acids is the distinctive element of olive oil compared to other vegetable fats.

Unsaponifiable Fraction

The minor constituents of olive oil, known as the unsaponifiable fraction, represent 1-2% of the total. This is the component that differentiates this product from other liquid fats and includes about 220 substances. Some of these components of olive oil have therapeutic value, others are the main part of the oil’s aromatic profile (flavors-scents), while others are effective natural antioxidants capable of giving the product resistance to aging. Among them, the following standout: hydrocarbons, tocopherols, phenolic compounds, alcohols, sterols, colored pigments, and secondary elements.

• • Hydrocarbons: They represent about 60% of the unsaponifiable fraction, with 60-70% being squalene (saturated hydrocarbon), which impacts the nutritional properties of oils, while the remaining portion primarily serves to assess the genuineness and quality of the product;
  • Tocopherols: In olive oil, tocopherols are present in the forms α, β, γ, and δ. 90% of the tocopherol component is in the α form, which is also the most biologically active and known as vitamin E. Tocopherols are natural antioxidants that inhibit the rancidity process of the product, and for this protective function to occur, the ratio between the quantity of vitamin E (mg) and that of polyunsaturated acids (g) must not be less than 0.79 mg/g;
  • Sterols: Oilseeds have a different sterol fraction composition depending on the species. In olive oil, where the β-sitosterol fraction predominates, the following sterols have been identified: cholesterol (predominant in animal fats), campesterol, uvaol, stigmasterol, clerosterol, erythrodiol, and β-sitosterol. These compounds serve as natural antioxidants and also verify the genuineness of the product because the sterolic fraction differs for each type of oilseed;
  • Phenolic Compounds: The phenolic compounds found in olive oil differ from those contained in olives, and their qualitative-quantitative aspects are heavily influenced by variety, ripening stage at harvest, and extraction process. Indeed, being water-soluble, a significant amount of polyphenols is removed during extraction with vegetation waters; moreover, it is known that enzymatic actions occurring during extraction lead to the breakdown into simpler molecules compared to those found in the olive. Virgin and extra virgin olive oils are the only vegetable fats that naturally contain appreciable amounts (50-500 mg/kg) of phenolic substances; the reference to virgin oils is not casual because any type of chemical manipulation or rectification carried out on this product can only completely destroy the natural phenolic content. The antioxidant capacity of polyphenols, highlighted by some researchers, has solidified the important role these compounds play in the stability of olive oil; literature is rich with information spotlighting the positive correlation between the total quantity of polyphenols in virgin oils and their resistance over time to oxidation (induction period). Furthermore, researchers have highlighted the synergistic action between polyphenols and α-tocopherols (vitamin E) on the stability of extra virgin olive oil;
  • Colored Pigments: They give olive oil its characteristic colors, represented by chlorophylls and carotenoids. The chlorophylls a and b give newly extracted oils their intense green color, with levels ranging from 0 to 10 ppm, and they also vary depending on cultivar and maturity stage of the fruits. These substances deserve attention as they can act as pro-oxidants when exposed to light; in darkness, they synergize with phenols to protect against oxidation;
  • Alcohols: Alcohols can be aliphatic or triterpenic; they are found esterified in waxes and are of significant analytical importance for identifying oils obtained through solvent extraction or mechanical pressure;
  • Other Secondary Elements: This includes aldehydes, terpenes, esters, ketones, etc., which influence the aromatic note of the oil and thus compounds involved in its hedonic evaluation.

Here are some tips on why to consume extra virgin olive oil and why to buy olive oil directly from the mill!