Omega in your Body
Olive oil and health
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Mediterranean diet
In the Mediterranean basin, olive oil, along with fruits, vegetables and fish are considered major factors in preserving a healthy population. The growing popularity of the Mediterranean diet is due to the large body of epidemiological studies that show how the incidence of coronary heart disease (CHD) and certain cancers, e.g. breast and colon cancers, is lowest in the Mediterranean basin. Consumption of olive oil is also increasing in non-Mediterranean areas due to the growing interest in the Mediterranean diet and its healthful properties. Olive oil is the principal source of fat in the Mediterranean diet.
Olive oil production
Cultivation of olive dates back to biblical time. Olive oil is obtained from the fruits of Olea europea L., a tree that is best grown between the 30°-45° parallel. The Mediterranean countries supply more than 95 % of the world olive oil production of around 2,000,000 tons/year. Olive oil production is still mainly traditional farming, with a high number of farmers and mills, each employing its own traditional methods.
In the olive groves of Europe, the olive tree flowers in the spring and produces a small ovoidal bud, which develops into the mature drupe between October and January, depending on the area. Olive oil is obtained from the whole fruit by means of physical pressure, without the use of chemical solvents like most other vegetable oils. Intact olives are hand-picked at the right moment depending on the wanted properties of the finished oil product. They are immediately brought to the mill, crushed and pressed right away in a clean plant at temperatures below 25-30 C to yield a high-quality oil that is rich in minor constituents.
The initial step in production of olive oil is washing the olives to remove dirt, stones and other debris which may adhere to the fruit. The olives are then crushed in a hammer mill and the mixture of crushed olive pericarp and stones (the pomac) is finnally homogenized before pressing. The pomac is fed directly to the hydraulic press plates, each of which is covered by a filtering diaphragm, before the plate pile is loaded into the press for extraction. The oil is produced under pressure and after passing through the filter press, the oil is separated from water by a centrifugal clarifier, resulting in brilliant clear oil.
Olive oil grades in the market
Olive oil is classified into 3 different grades in the market; virgin, ordinary, or pomac. The most valuable kind of olive oil is the extra virgin one, obtained from intact olives that are quickly processed and cold pressed. Virgin olive oil that is submitted to a refining process loses some of the minor components, mainly phenolic compounds, and to a less degree squalene. By mixing virgin and refined olive oil an ordinary olive oil is produced and marketed. After virgin olive oil is produced the rest of the olive dupe and seed is again processed, submitted to a refining process, and the resulting pomac olive oil, to which a certain quantity of virgin olive oil is added, is then put on the market as a cheaper variety of olive oil.
Peculiar to olive oil is the abundance of oleic acid, a monounsaturated fatty acid (C18:1, Omega-9), which ranges from 56 to 84 % of total fatty acids in the oil, and the important minor components squalene and polyphenols. The content of the minor components of olive oil varies, depending on the cultivar, climate, ripeness of the olives at harvesting, and the processing system employed to produce. Olive oil produced from greener olives usually obtains higher taste scores because of its “fruity” and complex aroma, provided by its high polyphenol content. Olive oil contains the highest amounts of squalene of the vegetable oils, from 136 – 708 mg/100g (average 290 mg/100g in refined olive oils and up to 700 mg/100 g in extra virgin olive oil) and up to 500 mg/kg of phenolic compounds (Owen). The olive oils with high phenolic content are in general more bitter and greener than those with low phenolic content, and for some individuals the taste may be too strong.
Maturation of olive
During the growth and maturation period, several changes occur in the fruit. When the fruit is about 6 months old, the major phenolic components are the secoiridoid glucosides present in the pericarp, but as the olive reaches maturity enzymes release free oleuropein, which is the bitter principle of olives. During maturation, oleuropein undergoes hydrolysis and yields several simpler molecules that build up the well-known olive oil complex taste. These, along with several other transformation products, are able to cross the water/oil barrier and therefore become important antioxidants in the harvested oil. Hydroxytyrosol is particularly interesting as an antioxidant preservative because it is both hydro- and lipid soluble, thus useful in emulsion systems that contain both water and oil phases.
Bioactive properties of olive oil
The phenolic fraction, responsible for the stability and flavor of olive oil, is endowed with “pharmacological” properties. Phenolic compounds such as hydroxytyrosol and oleuropein in extra-virgin olive oil are powerful antioxidants, both in the oil and in the body. They have bioactive properties that support the effects of the Mediterranean diet being effective against oxidative stress associated health issues, including ageing, in a dose-dependent manner. Oxidative stress is defined as an imbalance between the oxidant and the antioxidant systems of the body in favor of the oxidants. Olive oil polyphenols are dose-dependently absorbed in humans, metabolized and excreted in the urine as glucuronide conjugates.
It is the unique profile of the phenolic fraction, along with squalene and oleic acid which confers the health promoting properties of olive oil. Squalene is to a large extent transferred to the skin. Its major protective effect is by scavenging singlet oxygen generated by ultraviolet light. The phenolic substances from olive oil are much more potent antioxidants than the classical free radical scavengers like vitamin E and dimethylsulphoxide.
The EUROLIVE study (a research project funded by the EU commission) aimed at assessing the beneficial effects of olive oil on human health, provided evidence of the protective role of the phenolic compounds from olive oil on lipids and lipid oxidative damage in humans at real life olive oil daily dosages. The polyphenols account for greater protection of blood lipids and oxidative stress damage than those provided by oleic acid. A phenolic rich olive oil may contribute to the dietary intake of biologically active compounds in quantities that correlated with good heart health. This was approved as a claim by the European Food Safety Authority (EFSA) in 2011. In vitro studies show that both hydroxytyrosol and oleuropein inhibit the oxidation of LDL cholesterol. Hydroxytyrosol also inhibits aggregation of platelets, prevents accumulation of the pro-aggregant thromboxane in human serum, the production of pro-inflammatory molecules such as leukotrienes and the inhibition of arachidonate lipoxygenase. These results indicate that biological activity of olive oil polyphenols goes beyond their antioxidant properties.
Written by Dr. Linda Saga and Ola Eide, BioActive Foods AS
References
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