New Hopland olive press in operation
An olive mill turns fruit into oil in about two hours, and the whole art lives in three steps: crushing, kneading and spinning. Understand those, and the difference between a great oil and a dull one stops being a mystery.
Watch olives become oil and it looks almost too simple. Fresh fruit goes in one end; two hours later green oil pours out the other. But inside those two hours are three decisions that make or break the result — how you crush the olives, how you knead the paste, and how you separate the oil. Get them right, with fresh fruit milled fast, and you get a bright, peppery extra virgin. Get them wrong and the same olives give something flat and tired.
Step one: crushing
First the olives are washed and de-stemmed, then crushed — stones and all — into a paste. This is where the oldest argument in milling lives. The traditional way is a set of huge granite wheels turning on a stone base, crushing slowly; the modern way is a compact metal mill with fast steel hammers or discs doing the same job in a fraction of the space. Many people believe stone-crushed oil comes out milder, rounder and fruitier, while steel gives a bolder, greener, more pungent oil because it works faster and cooler and preserves more of the sharp compounds. Both make excellent oil; they simply lean different ways.
Step two: malaxation, the quiet art
The paste then goes into a malaxer, a trough of slowly turning blades that knead it for a while. This gentle mixing lets microscopic oil droplets find each other and merge into pockets big enough to extract — without it, much of the oil stays locked in the paste. Millers call this the art of the whole process, and they are right: time and temperature here decide yield and character. Knead too warm or too long and you chase out more oil but lose aroma and can push the oil out of the extra-virgin grade. Every good miller is making that trade-off by nose.
Step three: the spin
Finally the kneaded paste is fed into a horizontal centrifuge, or decanter, that spins it hard enough to fling the heavy solids and watery fruit-juice one way and the lighter oil another. A second, faster separator polishes the oil clear of the last water. The leftover paste — the pomace — is trucked off to compost or further processing, and the oil is decanted into tanks. A tonne of olives yields very roughly 150 to 190 litres of oil, depending on variety, ripeness, weather and how soon after picking it was milled. Freshness is everything: the best mills press within hours of harvest.
| Granite stones | Steel hammer mill | |
|---|---|---|
| Speed | Slow | Fast |
| Footprint | Large, heavy | Compact |
| Typical style | Milder, rounder, fruity | Bolder, greener, more pungent |
| Heat | Gentle | Fast, kept cool |
| Verdict | Both make fine oil — different character |
What it means for the bottle
- Great oil is fresh oil — the best mills press within hours of picking.
- Crushing method shapes style: stone tends milder, steel tends bolder.
- Malaxation temperature is why real cold-extracted oil costs more and tastes better.
- Yield is only ~15–20% of the fruit’s weight — part of why good oil is not cheap.
How olive oil is made: common questions
How long does it take to make olive oil?
About two hours from whole fruit to oil at the mill — crushing, kneading (malaxation) and centrifuging — though the best oil is pressed within hours of the olives being picked.
Is stone-crushed oil better than steel?
Neither is simply better. Stone tends to give a milder, rounder, fruitier oil; steel a bolder, greener, more pungent one. Both make excellent extra virgin.
What is malaxation?
The slow kneading of the crushed paste that lets tiny oil droplets merge so they can be extracted. Its time and temperature strongly shape yield and flavour.
Why does ‘cold extracted’ matter?
Keeping the paste cool during malaxation preserves aroma and antioxidants and keeps the oil within the extra-virgin grade — but it sacrifices some yield, so it costs more.
How much oil comes from a tonne of olives?
Very roughly 150–190 litres, depending on variety, ripeness, weather and how quickly the fruit was milled after picking.
People obsess over stone versus steel, and it does matter — but not as much as freshness. A mediocre oil pressed hours after picking will beat a theoretically superior one that sat in crates for days going warm and starting to ferment. When you read a label, the words worth trusting are cold-extracted and a real harvest date; those tell you the malaxer was kept cool and the fruit was milled fresh. That is where the pepper and the green aroma actually come from.
Drawn from standard olive-mill practice: crushing, malaxation and centrifugal extraction.