Olive oil production
The words “olive oil” mean the product obtained from olea europea. It is composed of about 98 % of glycerides with the remaining 2% being various components naturally present in olives, some of which play a fundamental role in the olfactory and taste characteristics and which are also important for the stability and quality of the product.
|Olive-pomace oil production|
Olive oils and husk oils are classified on the basis of denominations and definitions from Regulation No 136/66/EEC of the Council of 22 September 1966 on the establishment of a common organisation of the market in oils and fats as it has been modified.
Extra virgin oils, virgin oils and ordinary virgin oils are edible; yet only extra virgin oils and virgin oils can be commercialised as they are for direct consumption. Ordinary virgin oils are commonly used mixed with refined olive oils and refined husk oils while acids oils (i.e. with acidity higher than 3.3 degrees) must be refined.
The quality of the olive oil depends on the ripeness of the olives, the type of harvesting (picking, shaking), the type of intermediate storage, and the type of processing carried out. Olives contain 38–58% oil and up to 60% water. Ripe olives should be processed as quickly as possible since lipases in the pulp cause rapid hydrolysis of the oil, impairing its quality for edible purposes. Top-grade oils are made from fresh, handpicked olives by comminution, pasting, and cold pressing.
Traditionally, olives were ground into a paste with stone mills; but today modern milling equipment is used. Milling is followed by mashing, possibly with the addition of salt. The pulp is then pressed and the press oil clarified by settling or centrifuging. Traditional open-cage presses are now being replaced by continuous screw expellers. The mashed pulp can also be separated in a horizontal decanter, the crude oil being recentrifuged after the addition of washwater.
An alternative is the use of machines to remove the kernels from the pulp, the residue then being separated in self-discharging centrifuges.
Cold pressing, which yields vierge grades (also referred to as virgin, Provence, or Nizza oil), is generally followed by a warm pressing at ca. 40°C, which gives an oil with a less delicate flavour. The yields depend on the equipment used. The press cake (pomace) contains 8–15% of a relatively dark oil, called Sanza or Orujo, which can be extracted with hexane and is used for technical purposes. After refining it is also fit for edible consumption.
Olive kernel oil is obtained by pressing and solvent extraction of cleaned kernels. It is similar to olive oil but lacks its typical flavour.
Cold-pressed olive oil is a valuable edible oil. Trade specifications are based primarily on the content of free fatty acids and flavour assessment. In some countries, warm-pressed olive oil with a high acidity is refined by neutralisation, bleaching, and deodorisation, and flavoured by blending with cold-pressed oil.
Pomace oil plants process the olive-pomace remaining after the extraction of oil from the olives. Oil is extracted with solvents resulting in crude pomace-oil and exhausted husks. Oil is sent to refineries and later used in the food industry, while exhausted pomace is mainly used as fuel.
Refined olive-pomace oils are mixed with virgin oils different from the lampante oils.