Olive Oil | How it’s Made

Olive oil has been a staple of Mediterranean cuisine for thousands of years, known for its healthy fats and rich, distinctive flavour. Discover the ancient knowledge and modern technology that make olive oil production possible.

Growing up in Spain and spending time in Greece and Lebanon, olive oil has played a starring role in almost every meal. I drizzle it on bread for breakfast or bake it into cakes, and nearly every savoury dish starts with sautéing onions and garlic in this liquid gold. Here’s how olive oil ends up on your table, step by step.

Step 1: The Olive Harvest – Timing is Everything

Olive oil begins in the orchard, where olive trees bear fruit once a year. Olives are typically harvested from October to March, depending on the region. The harvest’s timing is critical and varies depending on the type of oil farmers want to produce. For a stronger, more bitter oil, olives are harvested while still green, while ripe olives produce a milder, sweeter oil.^1,2 

Mechanical vs Traditional Harvesting 

Farmers can harvest olives by hand - more typical for small-scale farms - or by using machines that shake the trees for larger yields. Mechanical harvesting machinery gets the job done quickly, which is important when a harvest window is small, or farmers don’t have enough people to collect olives by hand. However, nighttime harvesting, valued for enhancing olive aromatics, has raised ecological concerns, as it can kill large numbers of migratory songbirds, which rest in the orchards and are vulnerable to machinery.³  To protect bird species, nighttime mechanical harvesting was banned in Portugal and Spain in 2020.⁴

Regardless of the method, the olives must be processed quickly after harvest to keep them fresh and prevent fermentation, which could lead to unpleasant flavours.⁵

In Italy, small producers still rely on manual harvest, often being a collective family activity. Nets are spread below the trees where olives are collected, to be then gathered in boxes.

The European Union (EU) accounts for about 65% of the world’s olive oil exports, with major markets in the U.S., Brazil, and Japan. Discover how a changing climate is affecting the industry.

Step 2: The Cleaning and Milling Process

After harvesting, farmers take olives to a mill for crushing, where they clean them to remove leaves, twigs, and other debris, ensuring only the fruit goes through the oil production process. Once the olives are clean, the mill crushes them into a paste— including the stones (or pits) and skin. Traditional methods used large millstones for this step, but today, most producers rely on steel rollers or hammer mills to break down the olives quickly and efficiently. Crushing releases the oil from the cells of the fruit, preparing it for extraction.⁶

 Mills can opt for traditional or modern crushing - here, the traditional stone presses crush the freshly harvested olives, transforming it into a past, the pomace.

Step 3: Cold Pressing – Where the Magic Happens

Farmers slowly stir the crushed olives, now a thick paste or pulp, in a process called malaxation. This step is critical because it allows tiny oil droplets to merge into larger ones. They gently mix the olive paste for 30 to 60 minutes at a low temperature. This “cold pressing” process helps preserve the oil’s natural flavours and health benefits.

By maintaining temperatures below 30°C during malaxation, producers ensure the preservation of antioxidants and a fresh, fruity flavour, which is especially important for producing extra virgin olive oil. The slower this step, the higher the purity and quality of the resulting oil.⁶

Step 4: Traditional Pressing vs the Centrifuge - Extracting the Oil and the Pomace

Once malaxation is complete, producers separate the oil from the rest of the olive paste. In the past, they used presses to apply pressure and squeeze out the oil. Today, producers mostly rely on centrifuges, which spin the paste at high speeds to separate the oil from the water and solids efficiently. This extraction process produces two distinct products: the valuable olive oil and a solid byproduct known as pomace.⁶

Pomace still contains a small amount of oil. Producers extract this olive pomace oil using chemical processes. Although it doesn’t match the quality of extra virgin or virgin olive oil, it is often used in industrial food production, cosmetics, or even as a fertiliser.⁷

In the traditional mill, the pomace is then spread onto weaved disks that are stacked and squeezed under hydraulic presses to extract the raw oil.

With olive oil prices climbing due to droughts in the Mediterranean, fake olive oil is becoming more common. Find out more about adulterated olive oil here.

Step 5: Filtering, Bottling and Optional Refining

The freshly extracted olive oil is sometimes left to settle, allowing any remaining particles or water to sink to the bottom. While some producers bottle the oil immediately, creating unfiltered olive oil with a cloudy appearance and stronger flavour, others filter the oil to remove any residual solids. Filtration results in a clearer oil.

Once filtered, the oil is stored in stainless steel tanks to protect it from light and oxygen, which can reduce its quality. Lower-quality oils may now go through the refining process - which includes heat and chemicals.  From here, it’s ready to be bottled and labelled, with attention to whether it’s extra virgin, virgin, or refined, depending on the production process and quality standards.⁶ 

Step 6: Quality Control – The Taste Test

Not all olive oils make the cut as the best - extra virgin - oil. After extraction, the oil undergoes sensory and chemical tests. A panel of trained tasters evaluates the oil’s aroma, taste, mouthfeel, and purity - ensuring no defects like rancidity or mustiness. Chemical tests assess the oil's acidity, peroxide levels, and phenolic compounds. If oils don’t pass these tests, producers classify them as lower grades, such as virgin or - after some extra processing - refined olive oil.⁸

Storage is key to conserving the quality of the extra virgin olive oil, which can turn rancid if kept in contact with oxygen for too long.

What’s the best way to store olive oil? Olive oil is a kitchen staple, but did you know it needs a bit of care to stay at its best? To keep it fresh and full of goodness, store it in a cool, dark spot, away from the stove or sunny windows. A tinted glass bottle works wonders for keeping light and air out. If you have a warm kitchen, you can pop your olive oil in the fridge to help it last longer. Don’t worry if it solidifies; it’ll return to its silky texture once it warms up again. For the best flavour and quality, try to use it within a year.

What's the difference between Extra Virgin, Virgin, and Refined Olive Oil?

The International Olive Oil Council grades olive oils based on their acidity levels and the extraction methods.

• Extra virgin olive oil (EVOO) is the highest quality and is made by mechanically pressing ripe olives, without using high heat or chemicals, which helps retain beneficial compounds called phenols. 
• Virgin olive oil is also made without chemical processing but has a slightly higher acidity level and, therefore, a different taste.
• Refined olive oil undergoes additional processing, making it milder in flavour and lower in nutrients, though it’s still widely used for cooking due to its higher smoke point.⁹

The Role of Terroir in Olive Oil Flavour and Aroma

Just like wine, the flavour of olive oil reflects the terroir—the unique combination of soil, climate, and geographical features where the olives grow. Olives from Spain, Italy, Greece, and other Mediterranean countries develop distinct flavours shaped by the specific conditions of their regions.^10,11 

For example, I have often heard that olive oil from Italy’s Tuscany region is known for its peppery and grassy notes, while Spanish olive oil from Andalusia tends to have a more fruity and nutty flavour.

Olive Oil’s Health Benefits

The health benefits of olive oil are often attributed to its antioxidant and anti-inflammatory properties. Observational studies even suggest that people who consume more olive oil may face a lower risk of cardiovascular disease, certain cancers, and dementia compared to those who use it sparingly or not at all.¹²

The Mediterranean diet, which features olive oil as a primary fat source, is widely regarded as one of the healthiest diets in the world. Studies suggest that the phenolic compounds found in olive oil contribute to its anti-inflammatory and antioxidant effects.¹³

The Traditional Skills Behind a Modern Olive Oil Industry

Though I’ve been more familiar with the taste of olive oil than water for most of my life, it wasn’t until I visited an olive mill on the Greek Island of Lesvos two years ago that I appreciated the precision and effort behind making this liquid gold. The process, from grove to bottle, carefully balances nature, tradition, science, and craftsmanship. Whether drizzled over a salad or stirred into cake batter, every bottle reflects the land where the olives grew, the hands that harvested them, and the knowledge passed down through generations.