Olive oil production: How to produce olive oil from process to machines, to extra virgin

Olive oil is much more than a simple condiment; it is a fundamental pillar of the Mediterranean diet and a true symbol of Italian culture, a product that inextricably links ancient tradition with technological innovation. From north to south, extra virgin olive oil is a major star on Italian tables, capable of uniting palates with its infinite variations: some prefer it bold, others more delicate, some fruity or with a spicy kick. Behind every drop of this “liquid gold” lies a complex yet incredibly fascinating olive oil production process, a journey that transforms a simple fruit, the olive, into an elixir of flavor and well-being. Understanding how to produce olive oil, knowing the different phases of olive oil production, discovering the role of olive oil production machines, and, above all, understanding how to produce high-quality extra virgin olive oil, means delving into a world of ancient wisdom and modern technology. This article serves as a comprehensive guide to explore each of these aspects, revealing the secrets behind one of the most beloved and appreciated products in the world.

How olive oil is produced: a journey from the olive to the bottle

The transformation of olives into oil is, in its essence, a mechanical process: it involves extracting the oily juice contained within the drupes. However, the quality and classification of the resulting oil depend crucially on how this process is conducted. There are several categories of olive oil, such as extra virgin, virgin, and lampante, and their distinction is based mainly on chemical parameters, like acidity, and on organoleptic analysis. Higher acidity, for example, often indicates olives that are not perfectly healthy or errors during the production process, leading to a lower classification of the oil. To obtain an extra virgin oil, the most prized category, it is imperative that the olives have undergone no treatment other than washing and crushing, and that the extraction occurs solely through mechanical means, without the use of chemical solvents or adjuvants. The quality of the oil, therefore, is not born by chance but is the result of meticulous care that begins in the olive grove, with the cultivation of healthy olives, and continues with scrupulous attention to every single phase of processing. The path to producing an excellent olive oil requires a constant dedication to quality, as every step, from harvesting to storage, can influence the final result.

The olive oil production process: a detailed journey

The olive’s journey to becoming oil follows a specific olive oil production process, where each step plays a decisive role in defining the characteristics and quality of the final product.

1. Harvesting the olives: the decisive moment for flavor

The first phase, harvesting, is universally recognized as one of the most important, as the final aromatic profile and flavor of the oil largely depend on it. The ideal harvest period varies based on the cultivar, geographical area, and the year’s climatic conditions, but it generally falls between September/October and November/December. It is essential to pick the olives at the right stage of ripeness, a process known as veraison, during which the fruit’s color changes from green to purplish and then to black. Olives harvested at this time are richer in juice and nutrients, which give the oil a more intense and complex taste. The choice of the precise harvest time represents a delicate balance: a later harvest may yield more oil but often at the expense of polyphenol concentration and aromatic complexity, while a slightly earlier harvest can enhance these latter characteristics.

Harvesting methods can be manual, such as hand-picking (brucatura), or combing (with special rakes), which ensure the fruit’s maximum integrity and are often reserved for the highest quality productions. There are also mechanized methods, such as the use of shakers or facilitators, which are more efficient for large quantities but require care to avoid damaging the olives. Regardless of the method, it is crucial to avoid bruising or damaging the fruits, as this can trigger undesirable oxidative and fermentative processes, compromising the oil’s quality even before it reaches the mill.

2. Storage and transport: a race against time for freshness

Once harvested, the olives begin a real race against time. This is a fundamental moment, sometimes mistakenly underestimated, but one that profoundly affects the final quality. The olives should be transported to the mill as quickly as possible, ideally within a few hours and no later than 24-48 hours after harvesting. This short timeframe is crucial to prevent the onset of abnormal fermentation and an increase in acidity, phenomena that would irreparably degrade the oil’s quality, making it impossible to obtain an extra virgin oil. If the olives are not processed promptly, even the best raw materials can deteriorate. While waiting, the olives must be stored in perforated crates that allow for aeration, kept in thin layers to avoid crushing and overheating, and placed away from heat sources and direct sunlight. Proper temporary storage is therefore as important as careful harvesting; post-harvest logistics and the mill’s capacity to process the olives quickly are determining factors. Delays or poor management in this phase inevitably lead to an increase in acidity and the emergence of defects, precluding the possibility of producing an extra virgin oil.

3. Washing and leaf removal: essential cleaning for a pure oil

Before starting the actual transformation process, the olives must be thoroughly cleaned. This phase involves removing leaves, twigs, soil, and any other impurities that may have been collected along with the fruits. Washing, done with potable water, is a fundamental step not only for compliance with hygiene standards but also for ensuring a higher quality oil. Residues like soil or leaves, if not removed, could impart foreign and unpleasant flavors to the oil, such as the “earthy” or “leafy” defect, and could also accelerate degradation processes. Leaf removal and washing ensure that only healthy, clean olives proceed to processing, thus preserving the intrinsic organoleptic characteristics of the fruit. It is a seemingly simple operation, but its correct execution is an indispensable prerequisite for the purity and quality of the final oil.

4. Milling or crushing: the transformation into olive paste

With milling, or crushing, we get to the heart of the processing: the olives, whole and including the pit, are fed into the mill to be compressed and crushed. The goal is to break the cell walls of the drupe’s tissues, particularly the pulp, to release the oil contained in the vacuoles and form a semi-fluid mass called “olive paste.”

There are two main approaches to this phase:

• Traditional methods: These involve the use of classic stone mills (molazze), large granite wheels that rotate slowly, crushing the olives.
• Modern methods: These use mechanical crushers, which are faster and more efficient. They can be of different types: hammer mills (where olives are thrown by rotating hammers against a metal grid), disc mills (olives pass between two toothed discs, one fixed and one rotating), or knife crushers. These modern systems allow for better process control and ensure higher hygiene standards. The choice of crusher type and its settings (e.g., the diameter of the grid holes in a hammer mill) can influence the particle size of the olive paste, the degree of emulsion between oil and water, and consequently, the final organoleptic profile of the oil, including the extraction of phenolic compounds.

A crucial aspect in this phase, especially when aiming to produce high-quality extra virgin olive oil, is so-called “cold crushing,” which means working while keeping the olive paste temperatures as low as possible, ideally below 27°C (80.6°F), to prevent overheating that could cause product oxidation and the loss of volatile aromas and precious antioxidants.

5. Malaxation: the art of uniting oil droplets

After crushing, the resulting olive paste is transferred to malaxers, stainless steel tanks equipped with helical blades that slowly and continuously mix it. This phase, called malaxation, is rather simple to explain but requires time and precision to be performed correctly. The main goal is to break the water-oil emulsions formed during crushing and to encourage the aggregation of micro-droplets of oil dispersed in the paste into larger, free drops, which can then be more easily separated in the next phase.

Malaxation is considered by many to be “the heart of the process, where the final quality of the product is determined.” During this slow mixing, strict control of two parameters is essential: temperature and time. To achieve a “cold-extracted” oil, the paste temperature must not exceed 27°C (80.6°F) (ideally between 20°C and 27°C), and the malaxation time should not exceed 60 minutes, although shorter times (30-40 minutes) are often preferred to best preserve the nutritional properties, polyphenols, and authentic flavors of the oil. Overly prolonged mixing or excessive temperatures could lead to paste oxidation, loss of volatile aromatic compounds, and the activation of enzymes that degrade quality. For this reason, modern technology offers solutions like the “Thermal Conditioning Module” to be installed after the crusher, which allows the paste to be instantly brought to the desired temperature before it enters the malaxers, ensuring optimal thermal control from the very beginning.

6. Oil extraction: separating the green gold

Once the olive paste has been properly malaxed and the oil drops have aggregated, the actual extraction takes place. This involves separating the oily phase from the solid phase (the pomace, consisting of skins, pulp, and pit fragments) and the aqueous phase (the vegetation water contained in the olives).

Here too, we can distinguish between traditional and modern methods:

• Traditional method (by pressure): The olive paste is spread on circular filter discs called “fiscoli,” which are stacked on top of each other and subjected to pressure in hydraulic presses. The oil and vegetation water flow out and are collected, then separated by decantation or centrifugation. This discontinuous method is less common today in large-scale quality productions due to the higher risks of oxidation from contact with air and the difficulty in maintaining optimal hygiene of the filter discs.
• Modern method (by centrifugation): This is the most widely used system today, especially in continuous-cycle mills. The olive paste is fed into a decanter, a powerful horizontal-axis centrifuge that, thanks to the difference in specific gravity, instantly separates the three components: the lighter oil; the vegetation water; and the heavier pomace. This method is faster, more hygienic, and allows for better process control, reducing contact time with oxygen and better preserving the oil’s quality. There are two-phase decanters (which separate oil and a wet pomace containing the vegetation water) and three-phase decanters (which separate oil, vegetation water, and pomace).

After extraction with the decanter, the oil can be further purified using vertical centrifugal separators, which remove the last small solid impurities and residual vegetation water, making the oil clearer and more stable over time. In this phase too, it is crucial to maintain low processing temperatures to avoid compromising the freshness and characteristics of the oil. Technological evolution has led to a significant improvement in efficiency and hygiene, with a direct impact on the ability to preserve the intrinsic quality of the oil.

7. (Optional) Filtration: clear or whole oil?

Once extracted, the oil may or may not be filtered. This choice depends on the producer’s preferences and the intended use of the oil.

• Filtered oil: Appears clear and bright. Filtration removes residual solid particles (mucilage, pulp fragments) and suspended moisture. This process makes the oil more stable over time, as these particles could eventually settle at the bottom (forming what is known as “sludge” or “morchia”) and trigger fermentation or rancidity processes, compromising the oil’s shelf life and aromatic profile.
• Unfiltered oil (or “mosto,” “novello,” “integrale”): Appears cloudy and veiled due to the presence of these suspended particles. Some consumers prefer it for its more “rustic” appearance and for a potentially richer aroma and flavor in the first few weeks after production. However, unfiltered oil generally has a shorter shelf life and is more susceptible to alteration; it is therefore recommended for relatively quick consumption, preferably within a few months of production.

Filtration, therefore, is not a matter of intrinsically “better” or “worse” quality, but rather a technical choice related to the desired stability and longevity of the product. For optimal storage and to prevent the onset of defects like sludge, filtration is often the most indicated practice, debunking the myth that “unfiltered” is always synonymous with superior quality.

8. Oil storage: preserving its properties

The last, but not least important, phase is the proper storage of the freshly produced oil. Even the best extra virgin olive oil can degrade quickly if not stored properly. The main enemies of oil are light, heat, and oxygen (air). Exposure to these agents accelerates oxidation processes, leading to rancidity and the loss of precious organoleptic and nutritional characteristics. A few hours of direct sunlight can make the oil turn reddish and rancid.

To best preserve the oil, it is necessary to:

• Use appropriate containers: For large quantities in the mill, stainless steel tanks are preferred, as they protect from light and are inert. For domestic consumption, the ideal material is dark glass (green or brown), which shields from light. Good quality tins can also be used, but if the tin is of poor quality, the oil might acquire a metallic taste. It is essential that containers are always tightly sealed to limit contact with air.
• Maintain an optimal storage temperature: The ideal is between 14°C and 18°C (57°F to 64°F), in a cool, dry place away from heat sources and excessive temperature fluctuations.
• Respect consumption times: A quality extra virgin olive oil keeps well for about 18-24 months from the production date (or better, bottling date, if the harvest year is indicated). Once the bottle is opened, it is advisable to consume the oil within 3-6 months to fully appreciate its freshness.

Proper storage is therefore the final act that ensures the consumer can enjoy all the qualities for which the oil was produced with such care.

Olive oil production machines and equipment: technology at the service of quality

The modern olive mill is where the centuries-old tradition of oil production meets technological innovation. The goal is twofold: to maximize production efficiency and, above all, to ensure the highest standards of hygiene and process control to obtain a superior quality oil. The olive oil production machines available today are the result of decades of research and development.

The main equipment that makes up a modern plant includes:

• Leaf Removers and Washers: These machines are placed at the beginning of the processing line. Leaf removers eliminate leaves, twigs, and other light debris using airflows or mechanical systems. Washers then provide a thorough cleaning of the olives with clean water, removing soil and residual impurities.
• Crushers: As mentioned, these replace the ancient stone mills. The most common are:

• Hammer mill: Olives are conveyed into a chamber where high-speed rotating hammers crush them by projecting them against a fixed grid. The degree of crushing is determined by the diameter of the grid’s holes.
• Disc mill: Olives pass between two toothed metal discs, one fixed and one rotating, which break and tear them. There are also knife or roller crushers. The choice of crusher type and its settings (speed, distance between crushing elements) influence the structure of the olive paste, particularly particle size and the degree of pit fragmentation, with repercussions on the extraction of phenolic compounds and the oil’s aromatic profile.

• Thermal Conditioning Module (TCM): This is a heat exchanger, often of the tubular type, installed immediately after the crusher. Its function is to bring the olive paste instantly to the desired temperature (by heating or cooling it) before it enters the malaxers. This ensures absolute temperature control from the earliest stages of paste preparation, optimizing malaxation times and subsequent mechanical action, and reducing oxygenation.
• Malaxers (or Malaxation Tanks): These are stainless steel tanks, generally closed to limit contact with oxygen (some advanced models, like Alfa Laval’s Atmosphera® malaxers, can operate in a controlled atmosphere or under vacuum), equipped with augers or helical blades that slowly mix the olive paste. Precise control of temperature (via jackets through which hot or cold water circulates) and malaxation time is crucial.
• Decanter Centrifuges: These are the heart of the modern extraction system. These high-speed horizontal centrifuges separate the olive paste into its components (oil, vegetation water, pomace) by exploiting centrifugal force and density differences. The paste enters the decanter’s rotating drum, the solids (pomace) settle on the outer wall and are evacuated by an internal screw, while the lighter oil collects towards the center and is discharged separately. The vegetation water is also separated.
• Vertical Centrifugal Separators: After the decanter, the oil can pass through a vertical separator, a very high-speed centrifuge that performs a final clarification, removing the smallest residual solid particles and suspended water droplets. This step contributes to greater clarity and stability of the oil.
• Bottling Machines: This final stage is crucial for preserving the oil’s quality until it reaches the consumer. Modern bottling lines, which can be semi-automatic or fully automatic, typically include fillers, cappers, and labelers. Fillers, often piston-driven with servomotor control for high precision, dose the oil into bottles, with anti-drip nozzles to prevent waste. Cappers securely apply the caps, while labelers affix the labels with all the necessary information. Some systems may also include the automatic placement of heat-shrink capsules. The hygiene of the containers and the absence of defects in the glass are fundamental to keeping the oil’s organoleptic properties intact.

Technological innovation does not stop here. Systems like Alfa Laval’s Olive Oil Booster combine various technologies to increase the yield of high-quality oils and, significantly, to enhance the extraction of antioxidant phenolic compounds. This shows how research in olive oil machinery is increasingly oriented not only towards quantitative efficiency but also towards improving the intrinsic quality and health value of the oil. It is no longer just about “squeezing more oil,” but about “squeezing a better and healthier oil,” responding to a growing demand for excellence from consumers and a greater scientific understanding of the benefits of extra virgin olive oil.

For small producers or those who want to try their hand at home production, there are also compact mini-mills or simple manual presses, albeit with different capacities and quality control levels.

The adoption of modern machinery and its correct management allow for superior control of critical parameters such as temperature, processing times, and contact with oxygen. This translates into less oxidative and enzymatic degradation of the olive paste and, consequently, a higher quality oil, richer in aromas, flavors, and beneficial compounds like polyphenols.

Below is a table summarizing the main differences between the traditional and modern production methods:

Table 1: Comparison of oil production methods: traditional vs. modern

This table highlights how modernization, while requiring greater investment, offers significant advantages in terms of process control, hygiene, and quality consistency—fundamental aspects for producing excellent extra virgin olive oils.

The excellence of extra virgin: how to produce high-quality extra virgin olive oil

Extra Virgin Olive Oil (EVOO) represents the pinnacle of quality in oil production. To bear this designation, an oil must meet strict parameters, both chemical and organoleptic, defined by European regulations. The term “Extra Virgin” is therefore not just a marketing label, but a true certification that attests to a superior production process and a specific product profile.

According to the law, an extra virgin olive oil must be obtained directly from olives and solely by mechanical means. One of the fundamental chemical parameters is free acidity, expressed in oleic acid, which must not exceed 0.8% (0.8 grams per 100 grams of oil). Furthermore, the oil must be free of defects in the organoleptic analysis (panel test) and have a fruity note.

At the heart of producing a high-quality EVOO is the concept of “cold pressing” or, more correctly, “cold extraction.” This designation guarantees that the entire olive paste processing (particularly malaxation and extraction) has occurred at a controlled temperature, constantly kept below 27°C (80.6°F). Working at low temperatures is essential to preserve the integrity of the oil’s most delicate components: the volatile aromas that define its bouquet, and the precious antioxidant substances, such as polyphenols and vitamins, which contribute not only to the flavor (bitter and spicy notes) but also to the well-known health benefits.

To ensure EVOO standards are met, every step must be meticulously managed:

• Impeccable raw material: Use only healthy, intact olives, harvested at the right stage of ripeness (veraison), and free from damage by pests or adverse weather.
• Timeliness: Minimize the time between harvesting the olives and processing them in the mill, ideally within a few hours and no later than 24-48 hours.
• Thorough cleaning: Meticulously wash the olives to remove any residue of soil, leaves, or other foreign material.
• Constant thermal control: Maintain low temperatures (below 27°C) in all critical phases: crushing, malaxation, and extraction.
• Maximum hygiene: Ensure the impeccable cleanliness of all machinery and mill environments to avoid contamination that could compromise the quality and purity of the oil.
• Adequate technology: Use modern machinery that allows for precise control of processing parameters and minimizes the oil’s contact with oxygen.

Polyphenols play a key role: they are natural antioxidants present in olives that pass into the oil during processing. They give EVOO its characteristic bitter and spicy notes (particularly noticeable in fresh, high-quality oils) and contribute significantly to its stability over time, protecting it from oxidation, as well as offering important benefits for human health. A high polyphenol content is generally considered an indicator of a premium extra virgin oil.

“Cold extraction” is therefore a fundamental method for preserving these qualities, but the oil must then pass all the required chemical and sensory analyses to be classified as extra virgin.

Below is a table summarizing the main quality parameters for an extra virgin olive oil, according to regulations and expert recommendations:

Table 2: Key parameters for quality extra virgin olive oil (regulation and indications)

These parameters, taken together, define the identity of an extra virgin olive oil, guaranteeing its authenticity and the high-quality standard that consumers expect.

Determining factors for a superior quality olive oil (beyond the process)

While the production process is fundamental, the quality of a superior olive oil is the result of a complex interplay of multiple factors that begin long before the olives enter the mill. Producing an excellent oil is a holistic art that requires a deep understanding of the entire ecosystem, from the plant to the bottle, and a constant commitment to quality.

• The Raw Material is Queen:

• Olive variety (Cultivar): Each cultivar (such as Coratina, Frantoio, Leccino, Taggiasca, Nocellara, etc.) has a unique genetic heritage that translates into distinctive organoleptic characteristics in terms of aroma, flavor (fruity, bitter, spicy), and polyphenol content. A “monocultivar” (or single-variety) oil is produced using only one type of olive, allowing its peculiarities to be fully appreciated.
• Health of the olives: Healthy, intact olives, free from pest attacks (like the dreaded olive fly, Bactrocera oleae) or fungal diseases, are the essential foundation for a quality oil. Damage to the fruit can trigger degradation processes that lead to defects in the oil.
• Optimal ripeness: As already emphasized, the timing of the harvest is crucial. Olives harvested at a not-too-advanced stage of veraison tend to yield oils richer in polyphenols and with fresher, more herbaceous aromatic profiles.
• Pedoclimatic conditions and “Terroir”: The type of soil, altitude, sun exposure, the year’s microclimate (rainfall, temperatures), and the agronomic practices adopted in the olive grove (the so-called “terroir”) profoundly influence the characteristics of the olives and, consequently, the oil derived from them.

• Agronomic Techniques:

• The cultivation approach has an impact. Organic farming, which excludes the use of synthetic pesticides and chemical fertilizers, aims for greater respect for the environment and consumer health. Comparative studies have suggested that organic oils, all other conditions being equal, may have higher levels of some beneficial compounds like α-tocopherol (vitamin E) and polyphenols. However, a conventionally produced oil made with great care can still achieve levels of chemical and organoleptic excellence.

• The Importance of the Miller:

• The experience, sensitivity, and meticulousness of the miller are decisive. It is the miller who, knowing the characteristics of the olives being processed and the potential of their machinery, adjusts the parameters of each phase (malaxation times and temperatures, crusher speeds, etc.) to best enhance the quality of the raw material. A good miller is almost like an “orchestra conductor” who harmonizes all the elements.

• Continuous Chemical and Sensory Analysis:

• For serious producers, chemical analyses (acidity, peroxides, K values, polyphenols, etc.) and sensory analysis (panel test) are not just tools for the final classification of the oil, but also valuable quality control checks throughout the production process and for product storage. They allow for the timely identification of any problems and for continuous improvement.

Ultimately, behind an exceptional extra virgin olive oil, there is often a story of passion, dedication, deep agronomic and technological knowledge, and an almost reverential respect for the fruit of the olive tree.

Conclusion: choosing and appreciating olive oil consciously

Understanding the complex journey of olive oil production, from the field to the bottle, and the crucial role of olive oil production machines and the meticulous phases of olive oil production, allows us not only to better appreciate the value of every single drop of extra virgin olive oil, but also to become more conscious and informed consumers. Knowing how to produce olive oil and, in particular, what the requirements are for obtaining an excellent product, gives us the tools to recognize and choose quality.

Transparency and traceability of the production process are becoming increasingly decisive factors for consumers seeking authenticity and guarantees. A high-quality extra virgin olive oil is not only a pleasure for the palate but also a precious ally for our health, thanks to its content of monounsaturated fatty acids, polyphenols, and vitamins.

To make more conscious choices, it is recommended to:

• Read labels carefully: Check the origin of the olives, the production year (or harvest campaign), the expiration date, and, if indicated, the cultivar(s) used.
• Prioritize quality: A price that is too low can be a red flag. The production of a true quality extra virgin oil has its costs.
• Taste and experiment: Tasting is the best way to discover the incredible variety of aromas and flavors that extra virgin oils can offer. Do not hesitate to try different oils to educate your palate.
• Store correctly: Once you have purchased a good oil, protect it from light, heat, and air to keep its properties intact.
• (When possible) Visit a mill: Seeing the production process live during the milling season is an educational and fascinating experience that can further enrich your understanding and appreciation for this extraordinary product.

Choosing a quality extra virgin olive oil means bringing to the table not just a condiment, but a piece of history, culture, and well-being.