Milling turns healthy olives into oil through reception, de-leafing and washing, crushing, malaxation, centrifugal separation and clarification or filtration. Speed, cleanliness and control of time and temperature matter more than the appeal of any single machine.
In everyday language "milling" means the whole journey through the mill; technically, breaking the fruit is crushing. Understanding the stages lets you better read terms such as cold extraction and recognise where quality or defects originate.
Reception, leaves and washing
The olives arrive in identifiable lots, are weighed, separated from leaves and foreign bodies and washed with clean water. Crushed fruit or fruit left in a heap for a long time can ferment: no machine fully recovers a compromised raw material. Batch traceability starts here.
Crushing
Hammer, disc or blade crushers break the pulp, skin and stone, creating the paste. Geometry and speed influence particle size, extraction and sensory profile. Traditional stone mills describe a different technology, not automatically a superior quality. The decisive parameter is the consistent management of the whole process.
Malaxation
The paste is slowly stirred to encourage the micro-droplets of oil to merge. Time and temperature are a compromise: more aggressive conditions can help the yield but increase the risk of losing aromas or speeding up oxidation. The miller adapts malaxation to cultivar, ripeness and the state of the paste.
Separation and filtration
The decanter separates the phases using centrifugal force; a vertical separator can complete the clarification. Filtration removes water and suspended particles, usually improving stability over time. The oil must then be protected from oxygen, light and heat in suitable tanks.
What cold extraction means
The designation is regulated and applies to oils obtained at temperatures below 27 °C throughout the processing chain under the intended conditions. It is not enough to guarantee goodness: healthy olives, short times, hygiene and storage remain essential for obtaining a high-quality oil.
Hygiene is a process parameter
Paste residues in the lines, unclean water or long intervals between washes can transfer odours and fermentation. A modern mill must have verifiable procedures, not just shiny steel. Asking how batches are separated and machines cleaned at the end of each shift is a legitimate technical question for anyone entrusting quality olives.
Two and three phases
In three-phase decanters more water is added and the outputs are oil, pomace and vegetation water; two-phase systems reduce the added water and produce wetter pomace. Configuration and settings influence yield and minor components. Saying "two-phase" or "three-phase" is not enough to predict taste: what matters is how the plant is run.
Oxygen and nitrogen
During processing and storage, contact with air can oxidise aromas and lipids. Some plants reduce oxygen in the malaxers, and tanks can be protected with inert gases. These are tools, not shortcuts: if the olives arrive fermented, a controlled atmosphere does not cancel the defect.
Questions to ask the mill
Ask about the average time between reception and crushing, malaxation temperature and duration, water management, filtration and storage method. Agree how the batch will be received and what data will be reported. A good producer–miller relationship turns milling from a standard service into a shared decision.
The hours before milling
Process quality begins before the olives enter the crusher. Crushed, dirty fruit or fruit left in sacks can heat up and ferment; no later adjustment fully eliminates these effects. The harvest should therefore end with quick transport in ventilated crates, batch identification and scheduled delivery. At the mill the olives are weighed, de-leafed and washed as needed. Each step must reduce foreign bodies without introducing dirty water, odours or waits that compromise the raw material.
The initial selection deserves attention: fallen, mouldy or badly damaged olives should not be mixed into a healthy batch. Asking how the processing queue is managed is as important as knowing the model of the machinery. An overloaded modern plant can produce worse results than a simpler but well-organised one. The producer must communicate quantity, cultivar and objective; the miller must explain timings, separation, cleaning and parameters. This collaboration creates the conditions for consistent, traceable milling.
A delivery sheet can accompany the batch with cultivar, plot, date, harvest hours and anomalies. It must not slow the work down: a page or a digital code is enough. The information helps the miller recognise the expected paste and the producer link the result to decisions. If several farms deliver at the same time, durable labels and cross-checking reduce mix-ups. Traceability begins before the weighbridge and continues all the way to the returned container.
Crushing: turning the fruit into paste
After cleaning and washing, the olives are crushed to break the cells of the pulp and stone and release the tiny droplets of oil. Hammer, disc or other crushers apply different stresses and can influence particle size, temperature and the availability of compounds. There is no absolutely best machine: what matters is the match between cultivar, ripeness, throughput and settings. A paste that is too fine or an unstable process can make separation harder or change the final profile.
The Italian term "molitura" is often used to mean the mill's entire work, while technically crushing is a specific stage. Distinguishing the terms helps you ask precise questions. Observe whether the plant is cleaned between incompatible batches and how residues are managed. Abnormal smells in the processing area, accumulations of paste and stagnant water are signs not to ignore. Visible steel is not enough: hygiene depends on procedures, frequency of washing and hidden points of the line.
During crushing avoid conclusions based only on noise or the look of the paste. Ask which settings are adapted and why. A producer does not have to control every command, but should understand the logic of the process. If you want to run a trial, agree on large enough batches and a single variable. Improvised comparisons on tiny quantities can be distorted by the inertia of the line and residues from the previous batch. The method makes the experiment interpretable.
Malaxation: time, temperature and oxygen
Malaxation slowly stirs the paste to encourage the oil droplets to merge and prepare for separation. Time and temperature influence yield, aromas and minor components. Staying within the conditions required for cold-extraction claims does not mean that every value below the threshold produces the same result. A difficult paste may need different handling from a ripe one; automatically extending the time in search of yield risks losing aromatic freshness. Decisions must follow the raw material and the objective of the batch.
Contact with oxygen is also relevant. Some plants reduce the air in the malaxers, but a controlled atmosphere is a tool, not a cure for spoiled olives. The miller should monitor the real temperature of the paste, throughput and duration, recording any variations. For the producer it is useful to ask which parameters were used, especially when comparing different harvests. Without data, a higher yield might depend on ripeness, water in the fruit or settings and not on the supposed superiority of a single technique.
To assess malaxation and yield, record temperature and duration together with the state of the olives. An isolated number does not explain the result. Taste the batch and observe stability after filtration and storage. If you change the time, keep harvest and plant as constant as possible. Collaboration with the miller should seek learning, not confirm a theory. A slight increase in yield may not be worthwhile if aroma and commercial positioning decrease noticeably.
Decanter separation and water management
The decanter uses centrifugation to separate the phases of the paste. In two-phase plants the added water is limited and a wetter pomace is obtained; in three-phase systems oil, pomace and vegetation water are separated with different handling. The configuration affects flows, by-products and composition, but does not on its own determine sensory quality. Throughput, temperature, dilution and settings must suit the paste entering the machine.
Adding water can ease some processes, but excessive use can carry away water-soluble components and change the result. That is why it is useful to know not only the number of phases, but how the plant is run. After the decanter, centrifugal separators can polish the oil by removing residual water and impurities. Every transfer must limit oxygen and contamination. A producer comparing mills should ask for data and taste similar batches, rather than judge by the declared technology without considering how it is run.
Water management should also be discussed from the point of view of by-products and the environment. Ask how water and pomace are treated under the applicable rules. An efficient process is not only about litres of oil, but about resource use, cleanliness and the destination of residues. In communication to the customer avoid simplifications such as "no water" if they do not precisely describe the line. Clear data strengthens credibility and helps compare plants in a complete way.
Filtration and storage after the mill
Freshly separated oil contains variable amounts of water and solid particles. Filtering promptly increases stability because it removes material that could ferment or generate sediments. Settling can be managed, but it requires suitable tanks, timely racking and control; letting the dregs settle in a bottle meant for months of storage exposes it to sensory risks. The choice between filtered and unfiltered must therefore be planned according to shelf life and market, not left to a more or less rustic appearance.
Storage requires suitable, clean and closed containers, a stable temperature and protection from light and oxygen. Full tanks and, where provided for, inert gas reduce contact with air. Batches must remain identifiable even after racking and packaging. An excellent oil leaving the separator can quickly lose quality in a hot storeroom or in transparent bottles. Milling, filtration and storage therefore form a single chain: assessing only the hours spent in the mill leaves out half of the work.
Before leaving the mill, establish where the oil will go and in which containers. Transporting it in improvised vessels and then racking it several times adds oxygen and risk of contamination. Prepare clean, dry, properly sized tanks and plan the filtration. Identify each container before filling. The work after the separator is part of the campaign: without adequate space and equipment, the pressure of the day easily leads to solutions that damage the batch.
How to choose and assess a mill
Visit the plant before the campaign and ask for concrete information: hourly capacity, booking system, cleaning, batch separation, average waiting times, filtration options and how the oil is returned. Check how olives and oil are identified, where the crates wait and what data are available at the end. A good counterpart explains limits and choices without promising a fixed yield. Be wary of those who judge quality only by litres produced or treat every cultivar the same way.
After processing, check the weight delivered, the quantity obtained and the match of the batch. Taste the oil methodically and keep samples, preferably in small, protected containers. If defects appear, document the date, smell, taste and storage conditions before drawing conclusions. Compare results over several harvests: a single day can be influenced by raw material or breakdowns. The right mill is not necessarily the nearest or the newest, but the one that combines hygiene, competence, transparency and compatibility with your production goal.
Assess the overall service with a grid: punctuality, cleanliness, separation, transparency of parameters, yield, sensory profile and after-processing support. Assign scores while it is fresh and review them after a few months. A mill can excel in the machinery but be weak in logistics, or vice versa. Your future choice should reflect which aspects are decisive for your product. Documenting prevents personal impressions or a single yield from driving a multi-year relationship.
In summary
Milling turns healthy olives into oil through reception, de-leafing and washing, crushing, malaxation, centrifugal separation and clarification or filtration. Speed, cleanliness and control of time and temperature matter more than the appeal of any single machine.
Learn more at Olio Pace
Olio Pace/collections/oli-extravergine-di-oliva
Discover the Olio Pace selection and choose the product best suited to your needs.
FAQ
Are "molitura" (milling) and crushing synonyms?
In everyday speech often yes; more precisely, crushing is the stage that breaks the olives.
How long should malaxation last?
There is no single time: it must be adjusted to cultivar, ripeness, plant and objective.
Do stone mills make a better oil?
Not automatically. Quality depends on the raw material and on control of the whole process.
Does filtering ruin the oil?
A well-managed filtration removes water and solids and can improve stability.
How much time can pass between harvest and milling?
As little as possible. Olives that sit, are piled up or are crushed develop heat and fermentation; ventilated crates and scheduled delivery help protect the raw material.
What does cold extraction mean?
It is a regulated designation for oils obtained below 27 °C under the intended conditions. On its own it is not a guarantee of quality if the olives, hygiene or storage are inadequate.
Is water added during milling?
It depends on the plant and how the process is run. Any addition should be limited and controlled, because it can affect separation and the water-soluble components of the oil.
What is the difference between two-phase and three-phase decanters?
They change the way oil, water and pomace are separated and the amount of process water. No system is absolutely better without considering settings and raw material.
Does removing the stone change the oil?
Destoning changes the paste and can alter yield and sensory profile. The result depends on cultivar and plant, so it must be assessed on the actual product.
How do you store oil straight out of the mill?
It must be protected at once from oxygen, light and heat in suitable, clean tanks. Clarification or filtration help remove water and particles that reduce stability.
