How is olive oil made? — From the olive grove to the bottle

How does an olive become a liter of extra virgin olive oil? The journey from olive grove to bottle is one of the oldest processing methods in food history — and at the same time, one where modern technology makes the crucial difference between a mediocre and an outstanding oil. We'll take you from harvest to bottling.

1. Cultivation and Ripening — What Happens Before the Harvest

The olive tree is a long-lived companion: trees 200, 500, sometimes 1,000 years old still bear fruit. In the Mediterranean region, they bloom in spring, the fruits ripen over summer and autumn, and are ready for harvest in late autumn to early winter.

The ripening of the olive determines the character of the oil:

• Early harvest (October/November, still green olives) — strong, intensely fruity oil with a pronounced bitter note and pungency. The yield is lower because the olive contains less oil. Premium lines are produced this way.
• Late harvest (December/January, black olives) — milder, rounder, with softer aromas. The yield is higher, the character less pronounced.

This single decision — harvest time — influences the finished oil more than most other processing steps combined.

2. Harvest — By Hand, with Shaker, or Machine

Three harvesting methods are common today:

• Hand harvesting — the gentlest method. Olives are stripped from the branches with picking combs, caught in nets, and filled into crates. The olive remains undamaged; the quality is optimal. But: extremely labor-intensive, hence the method for premium manufacturers.
• Shaker — a vibrating gripper shakes the olives from the tree. Faster than hand harvesting, gentler than full mechanization; standard at most good farms.
• Fully mechanical harvesting — a self-propelled machine drives through the rows and shakes the olives into the collection vessel. Fast and inexpensive, but only usable in intensively managed, low-growing plantations. Good farms do not use it for premium lines.

Important in every method: The harvested olives must go to the mill as quickly as possible. Every hour of delay increases acidity and impairs the oil. The rule of thumb for good manufacturers: pressed within eight hours of harvest.

3. Milling — The Olive Becomes a Paste

In the mill, the olives, including the pit, are processed into a paste. Two milling systems are common:

• Stone mill — the traditional method: heavy granite millstones crush the olives over several minutes. The slower milling heats the paste less; the oil is often described as "rounder" and more harmonious. Still used today in manufactories like Muraglia in Apulia.
• Hammer mill — modern industrial variant: steel hammers crush the olives very quickly. Higher yield, faster processing; standard in most modern facilities.

Both methods can produce excellent oils. More crucial than the milling system is temperature control afterwards.

4. Malaxation — The Slow Separation

The olive paste is placed in a slowly stirring container (malaxer) where the oil droplets combine and float on the water content of the olive. Important: The temperature must not exceed 27 °C — otherwise the oil loses volatile aroma components and can no longer be called "extra virgin olive oil."

The term cold pressed or cold extracted refers precisely to this temperature limit. For good manufacturers, it is a matter of course.

5. Separation — Centrifuge Instead of Traditional Press

The old image of the olive press — cloths with olive paste, heavy stone plates, dripping oil — has today almost everywhere been replaced by centrifuges:

• Two-phase centrifuge — separates paste into oil and solid components (pomace); no water in the process, lower loss of aroma components. The current standard for good manufacturers.
• Three-phase centrifuge — adds water, separates into oil, water, and pomace; simpler, but aroma losses are possible.

Some companies have also developed their own, gentler processes — such as the Mori technique from the Italian machine builder, which Olearia Schiralli uses to extract its Olio Crudo line under exclusion of oxygen.

6. Filtration — Or Deliberately Not

After separation, the fresh oil still contains very fine suspended particles that settle over time. Here the path divides:

• Filtered — clear, crystal-clear oil, longer shelf life, slightly less aromatic richness. Standard for most table oils.
• Unfiltrato (unfiltered) — slightly cloudy, with a fine sediment, more intense aroma, shorter shelf life. Premium lines such as Olio Roi Mosto Roi or Calvi Mosto Oro opt for this.

An unfiltered bottle that shows visible sediment after a few weeks is not a quality defect — it's by design.

7. Storage and Bottling — The Final Step

Freshly pressed oil is stored in stainless steel tanks under inert gas (nitrogen) until it is bottled. This protects it from oxygen. Bottling usually takes place in dark glass, ceramic (as with Muraglia), stainless steel, or opaque PET bottles for cheaper lines.

From this moment on, the clock starts ticking for the customer — the fresh oil is ready for its journey to the kitchen.

What Refined Olive Oil Is

Not every olive oil on the market is virgin. If the mechanically extracted paste has sensory defects (e.g., because the olives were stored too long, were diseased, or poorly processed), the oil is refined: chemically and physically treated, neutralized, and decolorized. The result is a tasteless and odorless oil that may no longer be sold under the term "virgin."

On supermarket shelves, refined olive oil is usually labeled as "olive oil" (without "virgin" or "extra") or as a mixture "of refined olive oil and virgin olive oil." Those looking for character and aromatic diversity choose the extra virgin class.

Frequently Asked Questions

What does "cold pressed" mean?

During processing, the olive paste is not heated above 27 °C. This is an EU requirement for the "extra virgin olive oil" class — good producers work this way anyway. So the term alone is not a premium feature, but a minimum hurdle.

How much olive oil do 100 kg of olives yield?

Depending on the variety and ripeness, between 12 and 22 liters. Early harvests (greener olives) yield less oil, but it is more intense. Late harvests yield more, but it is milder.

What is the difference between filtered and unfiltered?

Filtered oils are crystal clear, have a longer shelf life, and are slightly more neutral in character. Unfiltered oils (Italian non filtrato) are slightly cloudy, have a visible sediment, and more intense aromas. Both have their justification — premium lines are often unfiltered.

Why are some olive oils so much more expensive than others?

Three main factors: harvest time (early harvest = lower yield = higher price), choice of varieties (single-variety and rare varieties cost more), size of the manufactory (family businesses with manual labor have higher personnel costs). DOP and IGP seals also make them more expensive due to additional controls and restrictions.

What about the term "first pressing"?

Historically: In the multi-stage pressing method of stone presses, the first pressing was the highest quality. With modern centrifuges, there is only one pressing — the term has lost its technical meaning and is now more marketing.

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