The Olive Tree – Solar Power and Fertile Soil
Anyone who has traveled through the coastal regions of the Mediterranean knows the sight: olive trees with their characteristic silvery-green foliage accompany the hilly landscapes. Together with grapevines, fig trees, and citrus plants, they form the unmistakable image of the Mediterranean cultural landscape. Olive oil production begins right here – with these impressive trees.
More than 150 different olive varieties are known worldwide today, which – comparable to wine varieties – provide a remarkable range of flavors. The olive tree originally comes from the eastern Mediterranean. Even today, cultivation is concentrated there: more than half of the world’s 850 million olive trees grow in this region.
The temperate Mediterranean climate offers the olive tree ideal growing conditions. It requires plenty of sunlight, sufficient autumn rain, and tolerates only minor temperature fluctuations and short periods of frost. During the dry summer months, the tree sustains itself through its extensive root system, which can reach up to six meters deep. This allows it to survive even on stony, nutrient-poor ground.
With good care, olive trees reach an age of several centuries and can grow up to 20 meters high. Depending on the variety, a young tree bears its first fruit after four to ten years. A mature tree produces an annual average of around 20 kilograms of olives – which can yield about three to four liters of olive oil.
The Olive Harvest – Meticulous Manual Labor with Tradition
Harvesting the olives is a demanding step in olive oil production that requires the utmost care. The timing of the harvest significantly influences both the quality and the quantity of the resulting oil. Generally, as soon as the skin of the olives turns from green to purple, they are ready for harvest. Depending on the variety and location of the trees, the harvest season extends from October to February.
The producer determines the exact harvest time. If the olives are picked while green, the result is a more intense, slightly bitter oil. Fully or slightly overripe fruits, on the other hand, provide a milder, sweeter oil. Ultimately, the olive variety used or the combination of varieties also determines the unique flavor.
In many growing regions – especially on steep slopes – the harvest is still carried out by traditional manual labor. In flatter areas, vibrating machines or modern stripping devices are sometimes used, which treat the fruit much more gently than the previously common method of beating the branches with poles. In some regions with particularly low-growing trees (so-called super-intensive cultivation), fully automatic harvesting machines can even be used.
Irrigation systems are also increasingly being installed to make the harvest yield more consistent and to offset extreme dry periods. In some areas, however, this creates new ecological challenges.
The olive is extremely sensitive to pressure. If it is damaged during harvest, the quality of the resulting oil suffers significantly. For an optimal result, processing should take place within one to three days after the harvest. The faster the fruit reaches the mill, the more valuable secondary plant substances are preserved.
Good to know: Tree care – especially the annual pruning – and harvesting account for around 75% of the total production costs in olive oil production.
Olive Oil Production – How the Liquid Gold Is Extracted
In olive oil production, a distinction is basically made between two processes, which are nevertheless based on the same principle: the oil is extracted from the fruit exclusively by mechanical or physical methods – through washing, crushing, decanting, centrifuging, and filtering if necessary. Chemical aids or additives are not used.
The Traditional Pressing Method
When the olives arrive fresh and undamaged at the oil mill, processing begins: first, they are mechanically cleared of leaves and branches and gently washed.
The fruits then enter the so-called edge runner – a large, bowl-shaped device with upright, rotating millstones. There, the olives, including their pits, are ground into a uniform paste for about 20 to 25 minutes. This grinding process sets off an enzymatic reaction: the oil droplets separate from the solid fruit mass. At the same time, important fat-soluble substances are released, which are responsible for the aroma and nutritional value of the olive oil.
In the classic method, the resulting olive paste is applied to round filter mats, stacked, and then hydraulically pressed. The liquid obtained – a mixture of bitter fruit water and oil – is then separated in a centrifuge.
The result is a completely natural fruit juice, which is usually filtered. Depending on the climate, soil conditions, olive variety, and degree of ripeness, it can taste green and grassy or ripe and fruity, spicy or mild, strong or delicate. The variety of flavors in olive oil is greater than in any other vegetable oil.
This pressing process is a purely natural procedure: the olive paste is neither heated nor mixed with other substances. Traditional olive oil production particularly protects valuable secondary plant substances such as phenols and oleuropein.
The common terms “cold-pressed” and “first pressing” also originate from this historical method. Since November 2003, only olive oils pressed at a maximum temperature of 27°C have been allowed to use these labels in the EU.
The Modern Extraction Method
Modern continuous systems allow for steady processing with significantly higher capacity. This means more olives can be processed exactly at the optimal time of ripeness without the fruit having to be stored for long periods in front of the mill. Another advantage: the use of stainless steel components significantly improves hygiene during olive oil production.
The olives are first temporarily stored in ventilated containers and then transported via a conveyor belt to the cleaning station. There, leaves and twigs are removed before the fruits are washed and then crushed in a fast-rotating metal mill – depending on the plant, using the so-called hammer or sickle method. Some producers combine the traditional stone mill with modern extraction equipment.
The resulting paste is then stirred for about 20 minutes using a screw system – a process that experts call malaxation. During this phase, further enzymatic processes continue, giving the oil its typical aroma profile. Increasingly, the stirring process is carried out in the absence of air or even protected with inert gas to extend the shelf life of the oil.
Depending on the consistency of the paste, some water is added or the temperature on the side walls is regulated. The paste then enters a decanter, which separates oil, fruit water, and pomace in a single operation. A downstream centrifuge ensures the final separation of fruit water and pure olive oil.
Even with the modern method, the oil may only be labeled as “cold extracted” if the processing temperature does not exceed 27°C.
A particularly gentle variant of olive oil production is the so-called Sinolea method: here, the oil first drips slowly and gently out of the paste before the remaining paste is processed via the decanter. The result is of even higher quality if the olives are pitted before pressing – this method produces a quality close to so-called “flower oil” or “dripped oil.”
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Important Questions and Answers About Olive Oil Production
How is olive oil produced?
Olive oil production begins with the harvest of ripe olives, which takes place from October to February depending on the variety and region. The harvested fruit is then washed, crushed, and ground into a paste. The oil is separated from the vegetable water and pomace through pressing or centrifugation. This is a purely mechanical process—the oil is neither heated nor chemically treated. The result is a completely natural fruit juice.
What role does the harvest time play in quality?
The timing of the harvest significantly influences both the quality and the flavor of the olive oil. If olives are picked while green, the result is a more intense, slightly bitter oil with a powerful aroma. In contrast, fully ripe or slightly overripe fruits yield a milder, sweeter oil. Harvest maturity begins as soon as the skin of the olives turns from green to purple. The producer determines the exact timing themselves, thereby defining the character of the finished oil.
What is the difference between traditional and modern olive oil production?
In the traditional method, the olive paste is crushed with a stone mill and then pressed using hydraulic presses—this is where the terms “cold-pressed” and “first pressing” originate. The modern extraction method uses continuous systems: the olives are crushed in a high-speed rotating metal mill, the paste is malaxed for about 20 minutes, and then centrifuged in a decanter. The modern method allows for higher capacity and improved hygiene thanks to stainless steel components.
What do “cold-pressed” or “cold-extracted” mean for olive oil?
Since November 2003, only olive oils where the processing temperature did not exceed 27°C may be labeled as “cold-pressed” or “cold-extracted” in the EU. This temperature limit specifically protects valuable secondary plant substances such as phenols and oleuropein. In the traditional method, the term refers to pressing; in the modern method, it refers to extraction via decanter—in both cases, the temperature limit must be maintained.
How much olive oil does a single tree produce?
On average, a mature olive tree produces around 20 kilograms of olives per year. This yields approximately three to four liters of olive oil. Depending on the variety, a young tree bears its first fruit after four to ten years. With good care, olive trees can reach an age of several centuries and grow up to 20 meters high. Over 150 different olive varieties are known worldwide, providing a remarkable range of flavors.
What is the Sinolea method in olive oil production?
The Sinolea method is a particularly gentle variant of olive oil production. In this process, the oil initially drips slowly out of the olive paste without any mechanical pressure. Only then is the remaining paste processed further via the decanter. The result is of even higher quality if the olives are pitted before pressing. This method produces a quality similar to so-called “flower of oil” (Tropföl) and is among the finest olive oils.
What factors determine the taste of olive oil?
The taste of olive oil is determined by several factors: the climate and soil conditions of the growing area, the olive variety used, the degree of ripeness at harvest, and the production process. The variety of flavors ranges from green-grassy to ripe-fruity, spicy, or mild. During malaxation—the stirring of the paste for about 20 minutes—enzymatic processes continue, giving the oil its typical aromatic profile. The flavor diversity of olive oil is greater than that of any other vegetable oil.
Note: The answers are based solely on the content of this article.
