Extra virgin olive oil is made using purely mechanical means, primarily pressing or centrifugation, without the use of heat or chemical treatments.
Here's a breakdown of the process:
1. Harvesting the Olives
The process begins with harvesting olives. The timing of the harvest is crucial, as it impacts the flavor and oil content. Methods range from hand-picking (which is gentle and preserves fruit integrity) to mechanical shaking.
2. Cleaning and Preparation
Once harvested, the olives are cleaned to remove leaves, twigs, and other debris. They are then washed before proceeding to the crushing stage.
3. Crushing the Olives
The olives are crushed into a paste. Traditionally, this was done using large stone mills, but modern production often employs mechanical crushers. This paste contains the olive pulp, pits, and water.
4. Malaxation
The olive paste is then stirred slowly in a process called malaxation. This gentle mixing allows the small oil droplets to combine into larger ones, making extraction more efficient. The temperature is carefully controlled (typically kept below 27°C/80.6°F) to preserve the oil's quality and avoid heat degradation.
5. Extraction
This is where the oil is separated from the paste. There are two primary methods:
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Pressing: The olive paste is spread onto mats or disks, which are then stacked in a press. Pressure is applied to squeeze the oil out. This is a traditional method, and the oil obtained this way can have a more distinctive flavor profile.
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Centrifugation: The olive paste is spun at high speeds in a centrifuge. This separates the oil, water, and solids based on their densities. This method is more efficient and hygienic.
6. Separation of Oil and Water
Regardless of the extraction method, the oil still contains water. This mixture is separated using either:
- Centrifugation: The most common method separates the oil from the water through centrifugal force.
- Decantation: Less common, this involves allowing the water to settle at the bottom of a tank and then carefully removing the oil from the top.
7. Filtration (Optional)
Some producers filter the oil to remove any remaining sediment. This extends the shelf life of the oil and gives it a clearer appearance. However, some argue that filtration removes some of the beneficial antioxidants and flavor compounds. Unfiltered oil will often have a cloudy appearance.
8. Testing and Classification
To be classified as extra virgin, the olive oil must meet specific criteria:
- Acidity: The free acidity level must be less than 0.8%.
- Peroxide Value: A measure of oxidation; must be within acceptable limits.
- Sensory Evaluation: The oil must have no taste defects and possess positive attributes like fruitiness, bitterness, and pungency.
If the oil meets these standards, it is classified as extra virgin olive oil. Lower grades, such as virgin olive oil, have slightly higher acidity levels or sensory defects. Any olive oil that does not meet the virgin olive oil standard must be refined to be made palatable, but can never be considered "virgin" or "extra virgin" after refining.
