Extraction of olive oil
Extraction
The passage of olives from oil is carried out through 3 stages: pressing, kneading and extraction. Each of these operations must be carried out in the best way to safeguard the intrinsic properties of the oil.
The transition from olives to oil must be performed impeccably to guarantee the characteristic scent and unmistakable taste. There are three types of extraction plant:
- Discontinuous or traditional: they are those that use the ancient stone wheels, the molazze, which crush the olives by mechanical pressure. The dough obtained by pressing the olives is kneaded, that is to say agitated for a long time by an endless vine, in order to promote the aggregation of the oil-bearing micelles. At this point the paste is placed on particular nylon filter discs, the fiscoli, which stacked on each other and crushed in particular hydraulic presses, will leak oil.
- Continuous: the crushing is carried out by modern hammer crushers which crush the olives on a drilled cylinder. After kneading the oil is extracted by percolation-centrifugation or by centrifugation of the dough alone. The percolation consists in the separation of water and oil by thin steel blades that, entering and exiting the paste, for adhesion extract only the oil, which will drip on the outside. This method extracts 40% to 60% of the product. The remaining oil will be separated in a horizontal centrifuge called decanter, in which the high speed of rotation separates the dough, known as bagasse, from oil and water.
- Semi-continuous: the crusher to molasses directly follow the decanter. After extraction the product, an emulsion of water and oil, is separated by using a vertical centrifuge. The residue from processing is sent to the mills which, using special solvents, extract the last part of the oil. After extraction, each oil is subjected to strict tests to determine the product category and compliance with regulations. If the acidity, expressed as a percentage of free oleic acid content, will be less than 0.8% and the organoleptic characteristics will be "absolutely irreproachable" we will have an extra virgin olive oil (extravergine), otherwise we can have the virgin olive oil (maximum acidity 2%) or lampante olive oil (acidity more than 2%) or with organoleptic characteristics that make it directly edible.
