Producing olive oil is as old as time itself. To make the best olive oil, first of all you have to start with good olives.
For the best extra virgin olive oil it is essential that the harvested olives are dealt with promptly, usually within hours of being picked.
Cold-pressed olive oil used to be produced by hydraulically pressing the ground olive mash between circular mats. Today, decanters or centrifuges are used.
The important factor is that the juice is obtained as gently as possible because any heat generated will reduce the flavour and nutrient content of the oil.
First, large fans blow away all the leaves and any other unwanted foreign bodies. Then the olives, with their pits, are ground to a paste.
Traditionally this used to be done by stone mills but now, almost universally throughout Spain, it is done by hammer mills which are easier to clean and are less labour-intensive.
Once the oil is decanted, it is passed through a series of large settling tanks to clear the oil of impurities and is then placed in bulk containers which are maintained at a constant temperature.
To control the quality, the oil is kept in these tanks right up until the moment of bottling and shipping.
The shorter time olive oil spends in transit, with its inevitable temperature changes, the better the product will be on your table.
Click on the links below for more info on olive oil.