Post actualizado el día octubre 25, 2026 by DeiviSanzPlay
Extra virgin olive oil doesn’t come out of a machine by magic. Behind every bottle there’s a chain of decisions that starts at the tree and ends in your kitchen. And if you’re wondering how olive oil is extracted from the olive, the short answer is: it’s ground, malaxed and separated. The long answer explains why an 8-euro oil tastes awful and another one at 15 blows your mind.
I’ve visited mills, talked to millers and tasted oils fresh out of the decanter. I’ll tell you what really matters, without cheap romanticism.
Harvesting: the first point of no return
Before extracting a single drop, the olive has to fall from the tree. And half the batch is already decided here. The olive harvest takes place between October and January, depending on the area and the variety. Picual, arbequina, hojiblanca, cornicabra… each one has its optimal window.
The traditional method is hand-picking: running your hand through the branches and letting the fruit fall onto a net. It’s slow and expensive, but the olive arrives intact. Beating, striking the branches with a pole, is faster but mistreats the tree and the fruit. And then there’s the mechanical shaker, which shakes the trunk and brings everything down at once.
The number one enemy here is time. An olive that spends more than 24 hours on the ground starts to ferment and develop free fatty acids. That translates into an oil with defects: moldy, damp, vinegary flavors. Serious millers grind the same day. Period.
Cleaning and washing: removing what isn’t olive
The olives arrive at the mill with leaves, twigs, dirt and stones. Before grinding, they pass through a cleaner that blows air and separates all that out. Then they’re washed with cold water. If you skip this step, the oil comes out with strange flavors and wears down the machinery.
Here you can already see whether the producer is careful or just going through the motions. A poorly done wash leaves residues that later show up in the tasting. It’s not a minor detail.
Grinding: breaking the olive to release the oil
We come to the core of how olive oil is extracted from the olive. Grinding consists of crushing the fruit until you get a paste. Traditionally, granite stones rotating on a concave base were used. Today hammer or disc mills dominate, spinning at high speed and breaking the fruit’s cells.
The goal is to release the oil droplets trapped inside the cell vacuoles. If you grind too fine, you emulsify the oil with the water and it then becomes hard to separate. If you grind too little, you leave oil inside the paste and lose yield. The exact point is an art.
Key fact: the temperature during grinding must not exceed 27 ºC. If it goes higher, we’re talking about refined or low-quality oil. The «cold» label isn’t marketing, it’s a physical reality.
Malaxation: the phase almost nobody explains well
The olive paste goes into a stainless steel malaxer, where it’s stirred slowly for 30 to 90 minutes. This is called malaxation of the olive paste and it serves to make the oil droplets join together and separate from the water and solids.
There are tricks here. Some producers add a little hot water to make separation easier, but that drags away polyphenols and reduces the bitterness and pungency, which are precisely what makes an extra virgin great. Others extend the malaxation to gain yield, at the cost of losing aromas.
My opinion: if an oil doesn’t bite or taste bitter, be suspicious. A real extra virgin has character. Cold malaxation without added water is the hallmark of mills that respect the fruit.
Separation: press, centrifugation or decanter
This is where the process forks. There are three systems for separating the oil from the rest:
- Hydraulic press: the classic method. The paste is put into fiber mats and pressed. You get oil, water and pomace. It’s slow and artisanal, but it produces very aromatic oils.
- Decanter centrifugation: the most widespread system. The paste enters a horizontal centrifuge that separates by density: oil on one side, water and solids on the other. Fast, continuous and with good yield.
- Two-phase system: it adds no water and generates less alpechín (wastewater). It’s the most ecological, although the oil may come out with more moisture.
The decanter is king today. It allows processing tons per hour without losing quality if the temperature is controlled. The traditional press survives in small mills and niche oils, but it isn’t better because of the system. I’ve tasted mediocre pressed oils and spectacular decanter ones.
Filtration and storage: where everything is ruined if you fail
Freshly extracted oil is cloudy, with traces of water and fine particles. It can be filtered or left as is. Filtration extends shelf life and prevents fermentation, but many tasters prefer cloudy oil because it retains more volatile aromas.
Storage is critical. Oil fears three things: light, heat and oxygen. It’s kept in stainless steel tanks, under nitrogen or in dark bottles. If you see a transparent bottle on a shelf in the sun, run. That oil is already oxidized.
Olive oil extraction doesn’t end at the mill. It ends when you open the bottle and smell freshly cut grass, artichoke or green tomato. If it smells rancid or of nothing, the process failed at some point.
Yield and quality: what nobody tells you
A kilo of olives yields between 150 and 250 ml of oil, depending on variety and year. That means a one-liter bottle requires about 5 kilos of fruit. Yield is measured as a percentage of dry matter and varies a lot.
But watch out: more yield isn’t better. Forcing the machine to squeeze out every last drop usually gives green, bitter oils with defects. The best oils in the world are obtained by sacrificing yield. It’s the paradox of extra virgin.
The next time you buy oil, look at the harvest date, not the best-before date. An oil from the 2025-2026 harvest will be at its best now. One from two years ago, even if it hasn’t expired, is no longer the same. And that, my friend, is also part of how olive oil is extracted and preserved.
