Manufacturing Of Olive Oil

The primary ingredient of olive oil is the oil that is expressed from ripe olives. In the late spring, small flowers appear on the olive trees.

Wind pollination results in the blossoming of the olives, which reach their Olive Oil peak oil content approximately six months later.

Thus, the olives are harvested from November to March, after they have progressed in color from green to reddish violet to black. It is often necessary to harvest olives from the same trees several times in order to gather olives at the same stage of maturation.

Since ancient times, workers have knocked the fruit from the trees with long-handled poles. The process has not changed significantly over the centuries.

Modern poles resemble rakes. Originally, nets were spread under the tree to catch the falling olives. Many producers are now using plastic covers to cushion the fall and to allow for cleaner, faster gathering.

One quart (0.95 L) of extra virgin olive oil, the highest level of quality, requires 2,000 olives. The only added ingredient in extra virgin olive oil is the warm water used to flush away the bittemess of the olives, caused by the presence of oleuropein. Extra virgin olive oil contains not more than 1% oleic acid.

Pure olive oil, that which results from the second pressing, is often mixed with extra virgin olive oil. The commercial, or non-edible, grades are put through a refining process that may leave traces of soda solutions and bleaching carbons.

The Manufacturing

Process

Collecting and grading the olives

* 1 After the ripe olives have been combed from the trees, they are picked over by hand to weed out unsound olives. The olives are divided into categories according to their plumpness, state of ripeness, and quality.

Then the olives are taken to the press and stored for a short period of time, from a few hours to several days.

The period is short enough to prevent fermentation but long enough to allow the olives to get warm so that they release their oil easily.

Washing and milling the olives

* 2 The olives are rinsed in cold water and then passed along a conveyer belt between rollers or continuous hammers.

This machinery, often called the olive crusher, breaks down the cells and de-stones the olives. Depending on the resiliency of the olives’ skin and the stage of maturation, it may be necessary to pass the fruit through the mill a second time.

Creating an olive paste through malaxation

* 3 In ancient times, the olives were mashed into a paste with a simple mortar and pestle. This principle was expanded upon until the stone mortars were large enough to require slaves or pack animals to operate them. In the modern process, the milled olives travel from the mill into vats in which slowly turning blades mash the olives into a homogenized paste.

Cold-pressing the olive paste to extract the oil

* 4 The oil is extracted by loading the paste into a hydraulic press. The olive paste is evenly spread over hemp pressing bags or disks covered with synthetic fibers. Each bag or disk is covered with approximately 9-13 lb (4-6 kg) of paste. Between 25 and 50 bags or disks are stacked onto a press plate.

Plate guides are inserted at intervals of five to six bags. The plates serve to maintain the balance of the stack and to distribute the pressure evenly.

A piston pushes up against the stack, and the oil seeps slowly through the pressing bags to attached tubes. The solid material remains inside the pressing bags.

* 5 The term cold-pressing refers to the fact that the oil is extracted without heating the paste, furthering insuring the purity of the oil.The oil that is expressed is a reddish mixture of the oil and the inherent vegetable water.

This is the oil that receives the appellation of “extra-virgin” olive oil. The paste is removed from the bags and run through several more presses to obtain the lesser grades of oil that remain.

Separating the oil from the vegetable water

* 6 Originally, the oil and water mixture was stored in vats until the oil rose to the top and was skimmed off. Some fermentation was inevitable, affecting the taste and smell of the olive oil. Today, the separation is accomplished swiftly by pumping the mixture into a centrifuge. The centrifuge is comprised of a rotating drum and an auger that are spun on the same axis at great speed. Because the oil and the vegetable water are of differing densities, the centrifuge forces them apart and into separate receptacles.

Storing and packaging the oil

* 7 The oil is stored in underground vats until it is ready to be shipped. Then the oil is canned or bottled on an assembly line. Cans or dark-tinted bottles will keep the deep-green color of the olive oil intact. Oil placed in clear-glass bottles will fade to a yellowish-green. However, the flavor is not affected.

* 8 In many cases, olive oil distributors purchase the olive from the producers and rebottle it. Packaging has become more ornate as the popularity of olive oil has grown.It is not unusual to purchase olive oil in unusually shaped bottles topped with netting or rope. Some packagers also hire professional artists to design their labels.

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