Spanish Olive Oil Production
In the two thousand years or so since the Ancient Romans made Spain the biggest producer of olive oil in the world, the production methods for this ‘liquid gold’ have changed very little. Though mechanical harvesting techniques have been developed, it is still far more effective, with less wastage, to harvest by hand and Spanish olive oil is still usually extracted by crushing the olives between two large round stones, just as was done in the heyday of the Roman Empire.
In Spain the olive harvest usually takes place from November to March, depending on the area, weather and the olive variety. Hand harvesting is done either by ‘milking’, stripping the fruits with half open hands onto nets spread to collect them or into baskets, or more often by beating the tree braches with sticks to dislodge the fruits, which are again collected on nets spread under the tree. Some premium olives are hand-picked straight into baskets to avoid damage and ensure the highest quality.
Once harvested the olives must be taken to the mill within 24 hours otherwise they start to spoil. Leaves and twigs are removed, the olives washed and then the whole olive is crushed to a paste between huge millstones.
The olive paste is then spread onto mats which are stacked and then pressed to extract the oil. The temperature must be kept below 27C at this stage, as heat can change the flavour and composition of the oil. The liquid extracted by this cold pressing is then left to stand for an hour, to allow the oil to separate from the water of the fruit. The oil is siphoned off, and left to settle, so that any particles fall to the bottom, then the pure oil can be decanted into bottles without any filtering needed. The whole process only takes a few hours, so olives picked in the morning can be eaten as pure new virgin olive oil with your evening meal that same day.
All the oil from the first pressing is virgin olive oil. It is tested for acidity levels before being designated extra virgin, fine/ virgin or ordinary olive oil. To be certified as extra virgin olive oil it must also pass a taste test by a representative panel of experts from the International Olive Oil Council, based in Madrid.
The paste left behind after the oil is extracted is called pomace. It is usually pressed again to extract any remaining oil. Pomace olive oil is usually flavourless and only recommended for use as a low quality deep frying medium.
More industrial methods of olive oil production use a centrifugal method to extract the oil from the paste after crushing and then again to separate the oil from the fruit water, filtering the oil to remove particles.
Needless to say, cold pressed, unfiltered extra virgin olive oil is considered the most desirable and is said to retain the most nutrients and so to be better for you.
Homer called it "liquid gold." The olive tree, symbol of abundance, glory and peace, gave its leafy branches to crown the victorious in friendly games and bloody war, and the oil of its fruit has anointed the noblest of heads throughout history.