What Is Oxidized Olive Oil? | An Expert’s Guide to Protecting Your Health
Posted by 綾亜矢子
Many people may think of olive oil as “good for your health.”
But is the olive oil you’re using really fresh?
In fact, some olive oils on the market have already oxidized, and may even have adverse effects on your health.
This article explains the basics of olive oil oxidation and how to choose high-quality products that have not oxidized.
|
Contents
|
People instinctively seek out “fresh” things
When we choose fresh vegetables over wilted ones at the supermarket, it’s not just about appearance or taste. Our bodies are seeking out “unoxidized—that is, unspoiled” food.
Our instincts include a sensor that tells us fresh means safe and nutritious.
This developed over the long course of human evolution, leading us to unconsciously recognize the risks of food that has gone stale.
Concern for freshness also reflects our awareness of health.
That is why we should be more interested in oxidation and take steps to avoid it.
Few people are alert to olive oil oxidation
Strangely, when it comes to olive oil and cooking oils, fewer people worry about whether they have oxidized.
One reason is that oxidation is “invisible.”
Another is the assumption that “oil doesn’t spoil, so it’s fine.”
This gap is precisely what can lead us to overlook health risks.
In fact, freshness matters for oil, too. As it deteriorates, it may adversely affect not only its taste and aroma but also the substances our bodies take in.
Because oxidation is invisible, we need to be careful.
What does it mean for olive oil to oxidize?
“Oxidation” in olive oil refers to changes in the oil’s components caused by exposure to air, light, or heat.
Oxidized oil not only loses its flavor; it is also known to adversely affect cells in the body when consumed.
Particular care is needed because “lipid peroxides” found in oxidized oil are thought to contribute to aging and lifestyle-related diseases.
Main causes of olive oil oxidation
Because olive oil is a natural product, it can oxidize readily depending on how it is stored and handled.
Unoxidized olive oil naturally contains distinctive aromas and flavors, as well as abundant antioxidants. But as oxidation progresses, not only are these benefits lost; substances that may adversely affect health can also form.
The four factors to watch out for in particular are light, air, temperature, and time.
If even one of these conditions is unfavorable, a high-quality oil can deteriorate in a short time.
Below, we’ll take a closer look at each cause of oxidation and how to prevent it.
Oxidation caused by light
Ultraviolet rays and fluorescent light accelerate olive oil oxidation.
Olive oil in clear bottles oxidizes much faster than oil in dark-colored bottles.
That is why many olive oils are sold in light-blocking bottles.
Oxidation caused by oxygen
When olive oil comes into contact with oxygen in the air, its unsaturated fatty acids oxidize.
Care is especially important after opening, when exposure to oxygen increases.
Oxidation caused by high temperatures
Oxidation accelerates sharply in environments above 25°C (77°F).
Avoid storing olive oil in places prone to high temperatures, such as near a kitchen stove.
If you’re buying olive oil at a supermarket, check that it isn’t displayed in a place that may get hot.
Natural oxidation over time
Oxidation naturally progresses over time.
The longer it has been since production, the more the quality declines.
When checking an olive oil label, be sure to look for the production date as well as the best-before date.
The reality of non-fresh olive oil being sold
Some of the olive oils we pick up believing they are “good for our health” have already oxidized.
Even when there is nothing visibly wrong with them, many people continue using them without realizing that they have lost their freshness.
This is because olive oil is inherently difficult to assess for oxidation by appearance alone.
Furthermore, the idea that “olive oil is good for you” is firmly established in the market, and consumers may be less cautious as a result.
But regardless of its appearance (or how attractive the label is) or price, oxidized oil may not only fail to benefit your health, but could even harm it.
Below, we’ll explain the less obvious risks of commercially available olive oil and some common misconceptions.
It’s difficult to tell whether store-bought olive oil has oxidized
Olive oil is difficult to assess for freshness by appearance alone.
You can tell whether vegetables are fresh by their feel and color, but olive oil is inside a bottle, making it difficult to see whether it has oxidized.
What’s more, oil does not spoil even after 10 years, so you cannot rule out the possibility that it has oxidized even if it looks unchanged.
Beware the misconception that all olive oil is good for you
Although many people believe that “olive oil is good for your health,” some olive oils that have oxidized are sold on the market.
In particular, when importers or retailers lack expertise in olive oil, products may be sold without adequate quality control.
So if you want to buy olive oil that is truly good for your health and has not oxidized, you need to choose a trusted expert or brand.
How to identify olive oil that resists oxidation
Olive oil is a delicate food whose rate of oxidation varies greatly depending on how it is stored and produced.
Even if you want to incorporate high-quality oil into your diet for your health, it is not easy to detect the invisible process of oxidation.
That is why it is important to know what to check before buying.
Below, we’ll explain three useful points for identifying olive oil that resists oxidation.
New products may be less prone to oxidation
If you’re choosing from the olive oils sold at a supermarket, choosing a new product is one option.
This may come as a surprise, but olive oil research has been underway for less than 150 years.
Therefore, oil made with the latest equipment rather than traditional methods may be less prone to oxidation, thanks to a faster and more hygienic process from harvesting and pressing through to bottling.
Rather than assuming “traditional means reliable,” it’s also worth considering whether the oil is made using the latest methods.
Choose a product with the most recent best-before date
Oil is sometimes called an “ultra-processed food.”
Refining at high temperatures and filtering improve its shelf life. Since it doesn’t spoil even years after production, consumers tend to pay little attention to its freshness.
However, a longer best-before date does not mean the oil is fresher.
So, naturally, a product with a more recent best-before date is likely to be fresher.
Buy from someone who knows their olive oil
Not everyone who sells olive oil necessarily knows a great deal about it.
Choosing a product handled by a trusted expert or importer can help reduce the risk of buying oxidized oil.
Products that clearly state the “harvest date” and “pressing date,” in particular, show a commitment to freshness.
Rather than judging by the packaging or image alone, consider the transparency of the information provided and the credibility of the origin and production methods.
Checking olive oil for oxidation after purchase
Even if you choose high-quality olive oil, it can oxidize depending on how you handle it after purchase.
Since oxidation is invisible, you may unknowingly compromise its flavor and health benefits.
That is why, even after you bring olive oil home, it is essential to know how to recognize oxidation and store it properly.
Below, we’ll explain in detail what to look out for when checking olive oil for oxidation after purchase.
Unoxidized olive oil smells and tastes different
Fresh olive oil may have an aroma reminiscent of fresh grass and a peppery bite.
As oil oxidizes, its flavor becomes dull, and it may develop an unpleasant smell.
Remembering how it smelled when first opened also makes it easier to notice changes over time.
Take care with storage after purchase, too
It’s important to take care when storing olive oil after purchase.
As a general rule, keep it in a cool, dark place away from direct sunlight, and use it up as soon as possible.
Oxidation is especially likely to progress after opening, so ideally, use it within one to two months.
Also, oil left around the spout increases the surface area exposed to air and can accelerate oxidation, so be sure to keep it clean after use.
Knowing how to choose olive oil that has not oxidized protects your health
Simply believing that “olive oil is good for your health” may lead you to choose oxidized oil.
That is why what matters is not “what you choose,” but “how you choose it.”
To experience the true appeal of olive oil, don’t assume that “you can’t go wrong with olive oil.” Take the time to choose carefully.
Hiromi Nakamura (なかむら ひろみ)
Olive Oil Planner / Italian home-cooking researcher / Representative Director, Olive Oil Stories Co., Ltd.
Serves as a judge for international olive oil competitions in Italy, Japan, Turkey, and other countries. Inspired by olive oil that brought out the best in simple dishes she enjoyed in Italian homes, she became an olive oil expert. Runs the “Cucina HIRO Italian Cooking Class.” Author of three books.