Olives and olive oil

The olive (Olea europaea) is a member of the Oleaceae, a family that contains jasmine, ash trees, and lilacs, to name a few. It grows as an evergreen shrub or tree and that can reach heights between 3 and 15 metres and live to be thousands of years old. Indeed, there is an olive tree in Brijuni, Croatia, that is around 1600 years old! Despite its advanced age, this plant still produces about 30 kg of olives per year! Clearly age really is just a number for this plant.

This plant has elliptical leaves, with a heart-shaped base, measuring 5-8 cm in length and 1-3 cm in width. When it blooms, small white flowers cluster on the tree, maturing in fall to fruits that are widely used. Olives are very popular, that’s why they can be found in many myths and legends, for example the Greek myth of Athena creating the olive tree as a gift to the city of Athens in order to become its patron deity.

As a result of its quality wood, the use of its fruits for food and oil, and the leaves being used in medicinal teas and tinctures, the olive tree has been very important to humans throughout history. It is difficult to pin down where this popular plant originally came from. Scientists seem to believe though that the wild olive originated in Persia and Mesopotamia, from where it was transferred to Syria, Asia minor, northern Iran, to the south of the Caspian sea, and to the Mediterranean. This plant is believed to have been growing in Greece since at least 2800 BCE, and has been widely spread around the Mediterranean region, from Africa to Spain. In the 15th century CE, this tree was also taken to South American by Spanish colonialists, spreading it to what is now present day Peru, Chile, and Argentina.

Cultivation rapidly spread across the Pacific coast of South America, where the climate is similar to that seen in the Mediterranean. It wasn’t until the 18th century that the olive made its way to North America, especially California, and it would not reach Japan until the beginning of the 20th century. Today, we also see it in Australia and New Zealand, and it is estimated that there are about 865 million olive trees around the globe, producing 300 million tonnes of olives each year! Additionally, there are hundreds of varieties of olive, with each having fruits that have different characteristics and that thus produce differing kinds of oils.


From olive to oil

Olive growing is a large-scale agricultural activity that involves cultivation of plants, production of fruits, and making of oil. The growers find themselves busiest in the fall as this is when the olives are harvested. Though some smaller growers still use manual picking methods involving tree shaking and collecting the fallen fruits, many now use machines. Another method (especially popular in Crete) involves leaving tarps under the trees for the olives to naturally fall onto. Though this is less demanding, the oil is of an inferior quality since some of the olives dry up before being used and thus produce lower quality oil.

To obtain the oil, the olives are mechanically pressed at 27 ° C, which produces a product with no chemical changes in the oil. For the best quality of oil, the perfect olives must be ground, blended, and centrifuged before being poured and filtered. Only water may be added during this process. Usually virgin olive oil (as opposed to extra virgin olive oil) goes through dry cleaning, or refining; with the help of steam, volatiles, odour, colour, and harmful substances are eliminated, but this also removes antioxidants. This oil is usually of a lesser quality than extra virgin olive oil. In addition to these types, olive-pomace oil can also be made by further extracting from the olive residues after the traditional oil removal process.

Take a look at this video to see the process being carried out in Italy:


Types of olive oil

Olive oils are grouped into various categories and sub-categories according to the process used to make them and various quality parameters. Virgin olive oils include extra virgin oils, which are the highest quality and are obtained directly from olives by mechanical means only and are neither chemically nor heat-treated. Extra virgin olive oil differs from regular virgin oils in that it has no sensory defects. At least 8 testers evaluate these defects, which may occur as a result of poor olive quality as some may ferment or go mouldy due to improper storage. In addition to sensory testing, there is also a UV spectrophotometric examination in order to determine the levels of peroxide and ethyl esters. This all being said, within the category of virgin olive oils we also find lampante olive oil, also known as light oil, which is unfit for consumption and is used for technical purposes. For dietary use, the oil needs to be processed and refined. Such refined oils are classified as a category, and the refining process does not change the triacylglycerol structure in the oil. Mixtures of refined and virgin oils are also included in this category. Another category, as we previously mentioned, is the pomace oil, obtained from solvent extraction of the olive residues. According to the blending of refined oils, they can then be further classified into several subcategories.


Chemical composition and effects on health

The main constituent of olive oil is fat, composed of glycerol to which fatty acids are attached. Unlike animal fats, which are dominated by the less-favourable saturated fatty acids, vegetable oils are primarily health-friendly unsaturated fatty acids. Olive oil is also very special among vegetable oils as it is predominantly mono-unsaturated fatty acid, also known as oleic acid after the olives from which it comes. This accounts for about 70% of the olive oil, while sunflower, corn, and hemp oils are all mainly composed of polyunsaturated fatty acids, most commonly called linoleic and linoleic acid after flax. As with other vegetable oils, olive oil is free from cholesterol.

The health benefits of olive oil are due to its oleic acid content, especially when this is used to replace animal fats and butter in the diet. Since it has virtually no saturated fatty acids, it does not promote cholesterol production in our bodies. The advantages of mono-unsaturated oleic acid from olive oil over polyunsaturated fatty acids from other vegetable oils have not been so thoroughly studied. One advantage is that mono-unsaturated fatty acids are more stable and less susceptible to oxidation and the formation of harmful radicals than are polyunsaturated fatty acids. On the other hand, a certain amount of polyunsaturated fatty acids are essential in our bodies as omega-3s and omega-6s are essential fatty acids.

Olive oil contains about 0.5% polyphenolic antioxidants, mainly tyrosol and oleuropein; the latter was named after the Latin name for the olive, Olea europea. These antioxidants successfully protect our blood lipids from oxidation, thereby preventing atherosclerosis, as confirmed by the European Food Safety Authority – EFSA.

There are three ways in which olive oil prevents cardiovascular disease:

  1. It contains no cholesterol.
  2. It does not contain saturated fats that promote cholesterol production in the body.
  3. It inhibits the oxidation of blood lipids, thereby preventing atherosclerosis.

Olive oil is also a relatively good source of vitamins E and K, as one tablespoon of olive oil (13.5 g) provides as much as 10% of your daily needs. On the other hand, we need to be aware that olive oil is high in calories. Ingesting 20 tablespoons of olive oil covers our energy needs all day long, without consuming any essential protein, minerals, or most vitamins. Olive oil is therefore very healthy when used in place of other (especially animal) fats, but it is still not something to consume in excess.

So, how about different coloured olives? While, it turns out the difference between green and black olives isn’t what you might expect. The only difference here is harvest time, with green olives being harvested when they are the right size but not yet ripe. These olives are green-yellow in colour and tend to have a more bitter flavour. Partially ripe olives are already beginning to change their skin colour, while on the inside they are still greenish in color, while truly ripe olives are brown or black.

In addition to its roll in nutrition, olive oil is also an essential ingredient in cosmetics. In ancient times, olive oil was used for skin care, healing wounds and abrasions, as well as nail and hair care. Today it is still used in many soaps and other hygiene products.


Additional reading:

https://www.np-brijuni.hr/en/explore-brijuni/sites-worth-visiting/the-olive-tree-on-brijuni

https://efsa.onlinelibrary.wiley.com/doi/abs/10.2903/j.efsa.2011.2033

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