How Is Olive Oil Made? (Traditional and Modern Methods)
Olive oil is made by crushing olives into a paste, which is then gently stirred so that oil droplets can combine. The oil is extracted from this mixture by pressing or spinning it at high speeds to separate the oil from the pulp.
In this article, we'll take a look at both traditional and modern techniques used in olive oil production and how different grades (virgin, extra virgin, pure olive oil etc.) are made.
How Olive Oil Is Made: Step-by-Step
Olive oil production methods have evolved over time as technology has progressed. Though the principles remain the same, most commercially available olive oil is now made using modern equipment to increase efficiency and quality.
Here’s a step-by-step process of how olive oil is produced:
1. Harvesting
Timing the harvest is important because it impacts the flavour and aroma of the final product. Green olives, picked earlier in the season, yield a strong-tasting oil, while riper olives harvested later will produce a milder-flavoured oil.
Olives change colour as they ripen, starting with green and gradually turning into purple, brown, or black depending on the variety.
Once harvested, the olives are quickly transported to the mill. They must be processed within two days after harvest; otherwise, they start to rot.
2. Crushing
After de-leafing and washing, the olives are ground into a paste using a hammer mill. This process breaks the olive cells and releases the oil from the pulp.
To answer a common question: olive oil is not considered a seed oil. It’s more like fruit juice since it’s extracted from the flesh of the olives. Even if producers do not remove the olive seeds (called pits) before crushing, the seed matter is still not a primary source of oil.
3. Malaxation
The olive paste is gently mixed or kneaded, and the oil starts to coalesce or stick together. By carefully controlling the length of time and temperature during malaxation, producers can influence the flavour and overall characteristics of the olive oil. This step is important to ensure optimal yield.
4. Extraction
There are three ways to extract olive oil:
- Cold pressing is a natural and traditional method using pressure to extract the oil without excessive heat. The resulting oils, virgin olive oil and extra virgin olive oil, retain the highest quality and health benefits among all grades of olive oil.
- Centrifugation is a modern method that uses high-speed spinning to separate oil, water, and solids. It's the most common approach used by olive mills today due to its efficiency and higher yield.
- Percolation involves filtering the olive paste through special materials to extract the oil. It's a less common approach but can be used in combination with other methods.
It's important to note that virgin and extra virgin olive oils are always cold-pressed. When producing these high-grade oils, the entire process should not exceed 27°C (80°F) to preserve their distinct flavours and nutritional benefits.
Related article: Virgin and Extra Virgin Olive Oil: What's the Difference?
There's also what’s called olive pomace oil. After the initial extraction, any remaining oil from the leftover solids (pomace) is typically extracted using chemical solvents. It's not considered as high-quality as other olive oils due to the heat and chemicals involved in the process.
5. Filtration and Refinement
Filtration removes any remaining particles or impurities like olive fragments or water droplets from the oil. It clarifies the oil's appearance and extends its shelf life, but doesn't alter the oil's chemical composition or flavour profile. This step is optional for high-quality virgin oils, which can be sold unfiltered.
Refinement is a more intensive process typically used for lower-quality olive oils that do not meet standards (like olive pomace oil). These oils go through heating and chemical treatments to make them fit for human consumption. The result is refined olive oil with a milder flavour and a longer shelf life commonly labelled as pure olive oil or olive oil.
6. Storage and Bottling
Ideally, olive oil should be stored in a cool, dark place away from heat and light to maintain its freshness for as long as possible. Dark glass bottles and opaque containers are the best choice for olive oil storage since they protect the oil from light exposure that can cause deterioration.
As you can see, quality control matters a lot in olive oil production. The International Olive Council’s trade standards ensure transparency and consistent quality across olive oil grades, ensuring that consumers can select the olive oil that best meets their health and culinary needs.
How Is Olive Oil Traditionally Made?
Olive oil is traditionally made by crushing the olives with millstones, and the resulting paste is spread on fibre mats that are stacked on top of one another.
Applying pressure to the mats causes the liquids to flow down into a container. Since oil and water don't mix, the olive oil eventually floats to the top and is separated.
“The Invention of the Olive Oil Press” ca. 1600, Jan Collaert I
(retrieved from metmuseum.org)
Olive oil is deeply ingrained in the culinary heritage of the Mediterranean region, and here you’ll find remnants of ancient olive mills, as well as active community mills that still use traditional methods today. Major producers like Spain, Italy, Greece, and Tunisia have a long history of olive production and are the best places to look for traditionally-made olive oil.
Further reading:
Spanish Olive Oil: What Makes It Special?
