The process of drawing the oil out of olives is called “Pressing”. “Pressing olives” involves three distinct pressing processes. If you visit an olive press, you will invariably find machines that perform three functions: crushing, stirring, and separating. Olive presses has been evolving for over two thousand years, and arguments have raged for centuries about which crushers are best, which stirrers are best, and which separators are best. But there is no room for argument about the three stages of pressing.
- First, the olives must be crushed. For centuries olives were crushed by squeezing them under giant stone rollers, Today’s cleaner way is to grind them in stainless steel hammer mills. Crushing is an essential part of pressing olives because the impermeability of an olive’s skin, the firm structure of its flesh, and the hardness of its stone, make it is impossible to draw out the oil while the olives are whole.
- Secondly the crushed olives must be stirred, a process called ‘malaxing’. For centuries, the olives were malaxed by letting them slosh in the pit with the grindstones rolling around tham. Today’s quicker way is to stir the olive paste with rotating stainless steel blades in stainless steel tubs. Malaxing is an essential part of pressing, because most of the oil in olives is held in microscopic sacks called vacuoles, and the oil cannot get free until the skins of the vacuoles have been breached. The temperature should be in the mid-twenties Celsius – not so cold that the vacuoles cannot release the oil, not so hot that the oil loses its punch.
- Thirdly, the crushed and stirred olive paste must be put under pressure to separate the oil from the rest of the olive. For centuries, pressure was applied by squeezing the paste between two wooden plates, and some processors still regard this as the best method, although the plates are now steel instead of wood. The more common method today is to press out the oil with centrifugal force. Whatever the method, pressure is an essential to let the oil run free.
An olive press, with an unmistakeable and permeating olive smell, and the magic of the green-gold oil flowing from the press, is a matchless combination of traditional romanticism and unremitting work. The presser loves to hear murmurs of ‘beautiful oil’, and ‘good yield’ from the onlookers. Modern olive presses are hi-tech machines, but operators require skill and dedication to produce fine oil.
Good pressing requires finesse as well as technique. It is not just a matter of removing leaves and imperfect olives, or keeping the temperature right. It is also a matter of judging when the olives are optimally malaxed, how much pressure to put the paste under, and how much oil to draw out of the paste.
As explained on the Research page, we chose a centrifugal press because of evidence suggesting that the oil lasts better. We have a small press, which makes our operation more like home-cooking than factory production. We can lift and move and pour the oil by hand, without ever needing to pump it. With this approach, we try to “Let Nature do its best”.