Cultivating Olives for Oil   

Man has been cultivating olives for thousands of years – the earliest oil containers are thought to date back to around 3500BC. Throughout that time the basic process has been much the same – the olives are crushed to produce oil and the stone and skin discarded.

Olives are cultivated from the tree Olea europaea (coming from the Latin word ‘oleum’ which means oil). As with wine the flavour of the olive oil depends on the variety, the climate, the cultivation methods and the terrain. In terms of production the three main olive producing countries are currently Spain, Italy and Greece.

The scale of olive cultivation ranges from families with a few trees harvesting by hand enough oil for themselves, to the sort of large scale commercial operations which produce export quantities of oil.

The quality of the olive oil will reflect the care taken at each stage.  To produce the finest cold pressed extra virgin olive oil the olives will be harvested by hand, treated with the utmost care and pressed quickly.  This helps retain the finest taste and quality.

Harvesting the Olives from the Trees

Harvesting traditionally was done by hand with the ripe olives combed from the tree and gathered into nets. Now much of the commercial olive harvest takes place with the olives being shaken from the trees using mechanical methods.

Clip showing how machines can be used to shake olives from the tree

Olives being hand combed from the tree

Cleaning the Crop

The olives are often contaminated with twigs and leaves (an occasionally stones or grit) which left would damage both the milling equipment and the flavour of the olive oil. Both water and air are used to clean the olives before any further processing can take place.

Grinding the Olives to release the Oil

Once harvested the olives have to be ground to a paste to release their oil, then water is separated (often by centrifugation) and the final product bottled.

Malaxing

This refers to the process whereby the tiny oil droplets in the olive join up to produce larger ones.  If you pick an olive and roll it between your fingers you will feel this happen as the olive becomes softer and more liquid the more you handle it.  In a mill this is normally achieved by passing the olive paste through a trough with spiral mixing blades.

Separating out the Oil

By this stage in the process oil and water will be mixed together and normally the liquid is centrifuged to ensure the lighter oil comes to the top and can be filtered off.

Classification of Olive Oil

Olive Oil is regulated by the International Olive Oil Council and more than 85% of the world’s production is grown in countries which comply with the IOOC.  This body has produced a range of quality categories outlined below:

Extra-virgin olive oil comes from virgin oil production only, contains no more than 0.8% acidity, and is judged to have a superior taste. Extra Virgin olive oil accounts for less than 10% of oil in many producing countries.  

Virgin olive oil comes from virgin oil production only, has acidity less than 2%, and is judged to have a good taste.

Pure olive oil is usually a blend of refined and virgin production oil.  

Olive oil is a blend of virgin and refined production oil, of no more than 1.5% acidity.  

You will also find oil described as ‘first press’ and ‘cold pressed’ – the first press yields the most flavoursome oil and pressing the oil without heat results in a smaller amount of higher quality product.