How olive oil is made

Extra virgin olive oil is only crushed olives and a spinning centrifuge, with no chemistry at all.

stations: 6
things upstream: 1
raw source: 1
step from the ground: 1

The short version

Olives are crushed to a paste, stirred slowly so the tiny oil droplets merge, then spun in a centrifuge that separates oil from water and solids. If the oil is made only by mechanical means it counts as virgin, and extra virgin must also pass chemical and taste tests, including free acidity under 0.8 percent.

Strip the leaves and wash

Harvested olives pass through blowers and washers that remove leaves, twigs and dirt before milling. The quality of the oil depends heavily on the weather, the cultivar and the time of harvest.

Goes in
Olives
Crush to a paste

The whole fruit, pit included, is ground. Traditional stone mills keep the paste under the stones for 30 to 40 minutes. Modern hammer, blade or disk mills reduce the olives to paste in seconds.
Stir the paste slowly

The paste is churned gently in warmed troughs, usually for 20 to 30 minutes. Small droplets of oil bump together and merge into large ones that are easy to separate.

20 to 30 minutes
Spin out the oil

A horizontal centrifuge called a decanter whirls the paste so the heavy solids, the water and the oil split into layers. Older mills pressed the paste on stacked fiber disks and let the oil settle slowly by gravity.
Polish and filter

A second centrifuge clears out remaining water. Some oil is filtered to take out fine particles that shorten shelf life, and some is bottled unfiltered, which looks slightly cloudy.
Grade and bottle

Chemists test free acidity and tasters check for defects. Oil that fails the extra virgin standards is sold as a lower grade or refined and blended.

End of the lineOlive oil

Worth repeating

The world's largest olive oil mill, in Villacarrillo in Jaen, Spain, can process 2,500 tonnes of olives a day.
Spain alone makes 24% of the world's olive oil.