The procedure to get oil from the olives pressing depends on the quality and skill of the mill. As this can be critical to the quality of the oil, it is well worth the inconvenience to chose the best possible mill, even if that means travelling further.
There are two main kinds of mill: the Traditional, and the Continuous Mill.
The process of the Traditional Mill starts by clearing away any leaves, twigs, or debris from the crates. The olives are rinsed, and conveyed to a circular round tray of approx 3 metre diameter. Rolling on this tray are one or two circular grindstones. After about fifteen minutes the olives have been reduced to a dough-like paste, which after time is transferred onto circular metal wire mats. These metal mats are stacked, one above the other, to form a tower approx. one metre high. This tower, in turn, is rolled to a hydraulic press, and the tower is compressed to about half its height.
The ensuing mixture of oil and water flows into a centrifuge. After adding sufficient warm water, the oil is separated from the water.
Finally, the golden/green liquid is collected in stainless steel, airtight, vats.
This method of pressing olive oil, is still revered by many as being the only true authentic way that this process should be done.
Historic procedures or not, this method does have its shortcomings, – namely: irregular temperatures during the pressing sequence, which frequently rise above 30 C. This being the hottest permissible temperature for top quality oil.
The traditional system is totally unsuitable for producing organic oil, because the press cannot be cleaned, or decontaminated between consignments. Therefore it cannot certify biologic production.
The Continuous Pressing Method: also starts by clearing out the twigs and the leaves, and rinsing the olives down. The olives are then subjected to a chopping process, which reduces the olives to a chunky, fruity, mangled, texture, which in turn, is pushed into open containers in which a large stainless steel cork-screw tube turns, squeezes and mixes, pressing the olives into a paste. The controlled temperature is raised to a required 26 C to 30 C for best results. Depending on the size of the machine this process can take between half an hour to an hour and a half. There are two types of centrifuge, the first separating the water-and oil-liquid from the solid part of the fruits (sansa), the second separatesthe water from the oil. The one shows how much water has been extracted from the oil, while the other produces only the oil having discarded the water.
The advantage of this machine is that it allows a thorough cleaning and rinsing down of all the exposed parts between users. Even on this machine, although temperature control is easier, one needs to check that they do not rise too high. The optimal heat required is deemed to be 27 C. which will not affect the taste of the oil, nor negatively influence the benefits of vitamins and minerals.
There is no magic; in producing this finest olive oil, it is just as difficult or easy as described above, however, with the enormous choice in the shops, it is easy to get confused.
Luckily, you need look no further, – You have just found one of the best.