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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 Four and Final
From transport and display to storage and use: how do we preserve flavour and quality after the oil leaves the mill?
You may buy an excellent olive oil, only for it to lose much of its distinction before you reach the last drop, even though the bottle is intact and months remain before the date printed on it. Quality that was carefully built over a whole season can decline within hours of exposure to high heat, or weeks of storage next to the stove. The loss may start before purchase, in a hot truck or a brightly lit shop window, and then continue with every use if the bottle is left open or poorly stored.
Having followed the mistakes of the farm, the mill, storage and bottling, we reach the stage whose responsibility is shared by the parties on the final leg of the journey: the carrier, the distributor, the retailer and the consumer. Each has small decisions that can protect the quality achieved or squander part of it, from choosing transport conditions and display location to bottle size, pouring method and how long the oil is used after opening.
In this episode we explain how to avoid these mistakes, what deserves attention when buying, storing and cooking, and why oil needs a different time calculation once the bottle is opened, so you can enjoy its quality and look after it better to the last drop.
The integrity of the carton is part of the inspection. I also recommend checking for leaks, closure integrity and batch identity, comparing the trip's conditions with what was agreed, and verifying the remaining shelf life for marketing. Where there is a significant temperature deviation or doubt about the condition, the lot is set aside until it is assessed; oil should not be accepted on appearance alone, nor judged spoiled from a passing reading without considering its severity, duration and the condition of the product. [2]
It is useful for the producer and buyer to agree in advance on the sampling method, acceptance criteria and the procedure in case of disagreement, while keeping receiving records linked to lot numbers.
Displaying oil in the shop window may seem a successful marketing choice, but it exposes the oil to light and heat. The same applies to shelves near heat sources or above appliances that expel heat into their surroundings. International Olive Council guidelines warn against exposure to natural or artificial light and to heat sources during display. [1]
It is better to set aside a protected location, adjust the quantity on display to the rate of sale, and move first the bottles closest to their best-before date. Old batches should not be left behind new ones until they surprise the shop at the end of the season. [1]
The price per litre may be lower in a large container, but the saving fades if it stays open for a long time and the oil loses its freshness. The consumer should therefore choose a size that matches their rate of use, read the product information, dates and storage instructions, and buy from a trusted source. A green colour or an attractive bottle is not enough to prove quality. [4]
The International Olive Council recommends choosing quantities that can be used within about one to three months after opening, keeping the bottle tightly closed and properly stored. This is guidance for preserving quality, not a fixed period at the end of which all oil spoils; the oil's initial condition and the conditions of use make a difference. [5]
The date printed on the bottle depends on storage and handling conditions; it is not a guarantee independent of them. If the stated shelf life is one or two years, this does not mean the oil keeps the same quality for that whole period after opening. A "best before" date indicates that the product keeps its expected characteristics in the unopened package, provided the specified storage conditions are followed. [10]
After opening, air enters again with every use, and oxidation and loss of flavour can accelerate; so keeping track of the opening date and a short consumption period becomes more important than taking comfort in the printed date still being far away. In practice, choose a size you can use within about a month; the International Olive Council advises using the oil within one to three months after opening, i.e. about 30–90 days, keeping it tightly closed and away from light and heat. This is an indicative period for preserving quality, not a fixed limit at which all oil spoils; follow the producer's own instructions, especially if they specify a shorter period. [5]
Write the opening date on the bottle, and do not treat it as the start of a new shelf life that extends the printed date. It is important for producers to give clear storage and after-opening consumption instructions, and for those working in consumer education to repeat this message: the printed date applies to specific conditions, and oil quality after opening needs care and a suitable consumption period.
Easy access to the bottle does not justify placing it next to the stove or on the kitchen windowsill. Repeated exposure to heat, light and air speeds up oxidation. The bottle should be kept tightly closed in a relatively cool, dark place, away from detergents, paints and strong odours, and returned to its place after use. [5]
Nor should a newly bought bottle be left inside a car parked in the sun. Care is completed by choosing a pourer that can be closed, rather than leaving a spout open all the time.
In homes and restaurants, new quantities may be added continually on top of old leftovers inside a serving bottle. I recommend stopping this practice, and emptying, cleaning and drying the container thoroughly before reusing it, making sure it is suitable for food contact. Adding new oil does not return the old oil to its original condition. [3, 4]
When splitting a large container, use a small, suitable, tightly closing container that blocks light, and transfer into it an amount suited to near-term use, while minimizing pouring time and closing both containers. Keep the source information and dates, especially in restaurants, and never return oil that has been used for serving food or has touched food to the stock container. [5]
Olive oil may turn cloudy or partly crystallize at low temperatures, and become liquid again as it warms up. This change alone does not prove spoilage, and chilling is not in itself a reason to judge the oil as deteriorated. [4, 5]
On the other hand, the "fridge test" cannot prove whether oil is genuine or adulterated; tests by the University of California, Davis showed it is unreliable for judging purity or quality. When commercial verification is needed, laboratory testing and specialist sensory evaluation are the reference. [6]
Good olive oil is suitable for cooking, and it is wrong to generalize that it becomes unsuitable as soon as it is heated. But heat, exposure time and cooking method affect its components and flavour; a study simulating home sautéing showed a decrease in phenols as temperature increased, with compounds responding differently to time. [4, 7]
In practice, heating should be adjusted to the recipe, and the oil should not be left to heat empty for a long time or until it smokes. To enjoy the aroma of extra virgin olive oil, it can be used for dressing or added near the end of preparation when the recipe allows. Repeated use of frying oil without assessing its condition is not fixed by adding new oil to it; and there is no general rule for olive oil that makes a specific number of reuses suitable for all conditions. [7, 8]
A rancid or strange smell is a reason to stop serving the oil and review its source and storage conditions; it should not be treated as a natural, pleasant change with age. The bitterness and pungency characteristic of some virgin oils, however, are well-known positive attributes and do not, on their own, indicate spoilage. A single home test is not enough to prove that the oil matches the category stated on the bottle. [5, 9]
When the oil reaches the table, the results of decisions that began with tending the tree and timing the harvest come together. A producer can protect their reputation by sharing clear guidance with carriers and retailers, following up on customer complaints and batch test results, and using what they learn from the market as a basis for improving the next season.
This completes the episodes of the series "Olive Oil Quality from Tree to Table" on Zyot W Dhon. The care invested on the farm and in the mill deserves to continue to the end of the journey, where the consumer opens the bottle and gets to know the product through its aroma and taste; that is where the purchase decision is renewed and trust is built.
[1] International Olive Council — Best Practice Guidelines for the Storage of Olive Oils and Olive Pomace Oils, 2018, transport, distribution and display, Open original source
[2] Breschi et al. Simulation of Transport under Different Temperature Conditions: Effects on Extra Virgin Olive Oil Quality. European Journal of Lipid Science and Technology, 2022, 124, 2100242, Open original source
[3] Codex Alimentarius — Code of Practice for the Storage and Transport of Edible Fats and Oils in Bulk, revised 2015, Open original source
[4] University of California, Davis — Olive Oil Myths and Facts, Open original source
[5] International Olive Council — Consumer Guidelines on the Best Storage Conditions for Olive Oils and Olive Pomace Oils, November 2020, Open original source
[6] University of California, Davis — Olive oil fridge test does not reliably detect fraud, 2013, Open original source
[7] Domestic Sautéing with EVOO: Change in the Phenolic Profile. Antioxidants, 2020, 9(1), 77, Open original source
[8] Casal et al. Olive oil stability under deep-frying conditions. Food and Chemical Toxicology, 2010, 48, 2972–2979, Open original source
[9] International Olive Council — Method for the Sensory Analysis of Virgin Olive Oils, Revision 11, 2024, Open original source
