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The unsaponifiable fraction is the part of virgin olive oil that is not made up of fatty compounds. Although it accounts for only around 2% of the oil by weight, it contains many of the substances responsible for some of olive oil's most distinctive characteristics, including its colour, aroma and flavour, as well as compounds with antioxidant and anti-inflammatory properties.
Most of these substances are removed during the refining process. As a result, they are found only in virgin olive oils or, in much lower concentrations, in olive oils that are blends of refined and virgin olive oils.
The unsaponifiable fraction is made up of a large number of compounds, many of which are present only in very small amounts. Their concentration can vary considerably depending on the olive variety and the stage of ripeness at harvest. The different families of compounds can be found by clicking here.
Below, we explain the main compounds, either because they are major constituents of the unsaponifiable fraction or because they make an important contribution to the characteristics of olive oil.
These include phospholipids and waxes. Although present in small quantities, they are responsible for the occasional formation of mucilage and sediment with a gummy appearance inside the bottle.
Squalene can account for up to 40% of the unsaponifiable fraction. Its name is derived from sharks, as one of the earliest commercial sources of squalene was shark liver oil.
Squalene is also produced naturally by the human body. It is one of the main lipids found in the skin, where it helps maintain hydration, elasticity and flexibility. However, its natural production decreases with age, which is why many cosmetic creams and lotions contain squalene.
Its main application is in cosmetics. However, because of its antioxidant properties and its potential role in supporting healthy cholesterol levels, it is also being investigated for pharmaceutical and functional food applications.
Although squalene is found in many vegetable oils, virgin olive oil is one of the richest natural sources. As demand for squalene continues to grow, the cosmetics industry is increasingly interested in virgin olive oil as a sustainable source.
β-carotene is a precursor of vitamin A. It is a fat-soluble antioxidant that contributes to the normal functioning of the immune system. In some countries it has also been used as a dietary supplement to help protect the skin from the effects of ultraviolet radiation.
β-carotene gives olive oil its characteristic yellow-orange colour.
α-tocopherol, better known as vitamin E, is a powerful natural antioxidant that helps protect fats from oxidation. It plays an important role in the stability and shelf life of virgin olive oil.
The concentration of tocopherols varies according to the harvest date. Levels are generally highest in early-harvest olives and gradually decrease as the fruit ripens.
Polyphenols are naturally present in virgin olive oil and in many other plant-based foods, including wine. In olive oil they are largely responsible for its characteristic bitter taste. Among the most important polyphenols are hydroxytyrosol, oleuropein and their derivatives.
Polyphenols are among the main compounds responsible for the antioxidant properties of olive oil. They help protect the oil from oxidation and are widely studied for their potential role in protecting the body against oxidative stress.
Like α-tocopherol, polyphenols also contribute to the stability of the saponifiable fraction by slowing the oxidation of triglycerides.
Their concentration varies considerably depending on many factors, particularly the olive variety and the harvest date. Early-harvest Picual olive oils are generally among those with the highest polyphenol content.
The European Union currently allows a health claim for virgin olive oils containing at least 250 mg/kg of hydroxytyrosol and its derivatives, stating that olive oil polyphenols contribute to the protection of blood lipids from oxidative stress.
Another important phenolic compound in extra virgin olive oil is oleocanthal. It has anti-inflammatory properties similar to those of ibuprofen in laboratory studies and is responsible for the characteristic peppery sensation at the back of the throat. Research into its possible role in Alzheimer's disease and other conditions is ongoing, although the evidence is not yet conclusive.
Other studies have also investigated the potential anti-cancer properties of oleocanthal in certain types of tumour, although further research is needed before firm conclusions can be drawn.
As mentioned above, β-carotene is responsible for the yellow-orange colour of olive oil. The green colour comes mainly from chlorophylls.
The relative proportions of β-carotene and chlorophyll determine the wide range of colours found in virgin olive oils, from bright green to deep golden yellow.
Green olives contain higher levels of chlorophyll than ripe olives, so oils produced from early-harvest fruit tend to have a more intense green colour. As the olives ripen, chlorophyll levels decrease and the golden tones provided by β-carotene become more noticeable.
This group includes more than 100 different compounds, such as hydrocarbons, alcohols, aldehydes, terpenes and furans. Together, they are responsible for the characteristic aroma of virgin olive oil.
These compounds are present in very small quantities, making their analysis particularly complex. Like polyphenols, their concentration generally decreases as the olives ripen. They are largely responsible for the fresh, green and fruity sensory characteristics of virgin olive oil.
Because these compounds are volatile, they evaporate when the oil is heated. This is one of the reasons why high-quality extra virgin olive oils are extracted at low temperatures, helping to preserve their delicate aromas and flavours.