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Note: This article was AI-translated from Arabic and is currently under manual review. The author is not responsible for any translation errors. Please refer to the original Arabic text for the most accurate and authoritative information.
Olive Oil Quality from Tree to Table | Episode Three
How do we protect the quality of extra virgin olive oil after extraction and until it leaves the producer's facility?
A producer may win the quality battle on the farm and in the mill, then lose it inside a tank that looks still or a sleek, tightly sealed bottle. Oil does not stop changing once it is extracted, and some of the fresh aroma and stability it loses may begin to fade without any visible change to warn its owner.
Having covered the mistakes of growing and harvesting, and then the processing mistakes inside the mill, we now reach the stage of storing the oil and preparing it for sale. Here the producer's ability to keep what has been achieved is decided, through managing sediment, oxygen and temperature, choosing the package, controlling bottling and monitoring quality. The journey through shipping, shops and use comes in the fourth episode.
The cloudiness of new oil may carry fine water droplets, fragments of fruit tissue and microorganisms. If they remain during storage, they can allow enzymatic reactions and microbial changes that produce sensory defects. Trials have shown that delaying filtration can quickly lower the quality of some oils; but the speed of change varies with the oil, the components of its cloudiness and its storage conditions. [1]
A suitable method should therefore be chosen to separate moisture and suspended matter early, either by filtration or by careful management of settling and racking away from the sediment. What counts is separation efficiency and verifying the result, not a clear appearance alone. Filtration is an accepted physical process in the production of virgin oil and does not turn it into a refined oil; the International Olive Council standard sets a maximum of 0.2% for moisture and volatile matter, although this figure alone does not guarantee stability. [2, 3]
Closing the lid does not remove the air above the oil or the oxygen dissolved in it. Each time quantities are drawn from the tank, the headspace grows unless it is properly managed, while pumping the oil with splashing and turbulence can draw in more air. [4]
Protection begins with stainless steel tanks fit for purpose, tank capacities that suit the stock, and minimizing unnecessary internal transfers. The headspace can be protected with food-grade nitrogen or argon within a controlled system. What matters is monitoring the effectiveness of this protection after each draw-off, not just adding gas once at the start of the season. [2]
A store may be shaded yet hot, or air-conditioned while some tanks sit near a hot ceiling or wall. Heat speeds up oxidation reactions, so it must be measured and recorded at points that truly represent the oil's conditions, rather than relying on the feeling that the room is cool. [4]
A target of around 15 to 18 °C can be set for storing premium oils where adequate control is available, while avoiding large rises and proximity to heat sources. This is an operational storage target, not an independent limit for classifying the oil. The need for insulation or cooling depends on the location and how long the stock stays. [5]
Cleaning water or traces of old oil may remain at the bottom of the tank and in the drain valve, even though the walls shine. Traces of detergents or unsuitable materials may also enter from fittings and hoses. The inspection should therefore cover the tank and all its parts in contact with the oil, verifying that residues are removed and everything is dried before filling. [4, 6]
Copper or corroded parts in contact with the product must be avoided, as traces of some metals catalyse oxidation. The risk of residual water is not solved by simply adding new oil on top of it, but by fixing the cause of the retention and completing cleaning and drying. [4]
A beautiful bottle may not provide the protection needed. What is required is to assess its ability to limit light and oxygen permeation, and its suitability for contact with the oil throughout the expected storage period. Dark or opaque packages offer better light protection; clear glass can be protected with a suitable opaque cover, while metal containers need a suitable, intact inner lining. [2, 7]
The assessment includes the cap, gaskets and sealing efficiency, not just the body of the package. A "food-grade" specification does not, on its own, describe barrier performance against oxygen or light. I recommend testing the oil in the proposed package before committing to a large purchase, and evaluating the results during storage. [7]
Oil may be well preserved in the tank and then come into contact with excess air during bottling. Important details include adjusting pumping to reduce foaming and splashing, not leaving oil and open bottles exposed to contamination or unnecessary delay, and checking that closures are tight. [4, 6]
Oxidation is limited by reducing the oxygen in the headspace with a suitable technique, while leaving the space needed for thermal expansion and complying with applicable fill requirements. Filling the bottle to the brim is not a rule for good preservation, and injecting gas without verifying the procedure's effectiveness does not guarantee the result. [3, 7]
Professional blending of qualified oils can help keep a product's characteristics consistent, but it requires knowing every component and evaluating the final blend. Adding the remains of batches of unknown condition to new oil simply because the colour looks similar or the acidity is low may carry over a sensory defect or make it hard to trace the source of a problem. [6]
Each tank and filling batch has a record showing its origin, the dates of extraction, filtration, blending and bottling, and test results. I recommend keeping sealed, protected reference samples from bottled batches, linked to lot numbers, so the oil's condition at release can be compared with what appears during follow-up. [6]
The bottling date does not reset the oil's age. How long it keeps its quality depends on its previous condition, its composition, the package, oxygen, temperature and light. It is therefore wrong to copy a common shelf life onto every product without evidence suited to the oil and its conditions. [2, 8]
It helps to follow samples in the final package under storage conditions that represent reality, measuring oxidation indicators and carrying out periodic sensory evaluation. Accelerated stability tests can help if their results have been validated for this product, but they need scientific interpretation and comparison with real-time storage. [8]
Before releasing a lot, the producer reviews the analysis and tasting results, seal integrity, batch identity and the accuracy of the label data, and sets the best-before date according to applicable requirements. Stock is best moved according to which is closest to the end of its approved quality period, with an adequate margin for the time it will then spend on the market. [2, 6]
I invite every producer to review one batch from the moment the oil leaves the separator until its bottle is sealed: Was its sediment removed efficiently? How were its air and temperature managed? Was the package tested, or chosen for its looks alone? This review will reveal points where the season's value can be protected with a specific, practical change.
The sealed bottle carries to the buyer the sum of all the care that came before it. In the fourth and final episode of the series "Olive Oil Quality from Tree to Table" on Zyot W Dhon, we follow what can threaten that result during transport, handling, display, storage and use.
[1] Filtration Scheduling: Quality Changes in Freshly Produced Virgin Olive Oil. Foods, 2020, 9(8), 1067, Open original source
[2] International Olive Council — Best Practice Guidelines for the Storage of Olive Oils and Olive Pomace Oils, 2018, Open original source
[3] International Olive Council — Trade Standard Applying to Olive Oils and Olive Pomace Oils, Revision 22, June 2026, Open original source
[4] Codex Alimentarius — Code of Practice for the Storage and Transport of Edible Fats and Oils in Bulk, revised 2015, Open original source
[5] University of California, Davis — Olive Oil Quality, Open original source
[6] International Olive Council — Quality Management Guide for Olive Oil Packing Plants, 2006, Open original source
[7] University of California, Davis — Olive Oil Packaging, Open original source
[8] Application of accelerated shelf-life test (ASLT) procedure for the estimation of the shelf-life of extra virgin olive oils: A validation study. Food Packaging and Shelf Life, 2022, Open original source
