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What is Olive Oil?

Olive oil is extracted from olives, the fruit of the olive tree, scientific name Olea europaea. Olive trees originated in the Mediterranean area and are common in countries like Greece, Italy, Spain, and Portugal. In the United States, olive trees are mainly grown in California.

Olive oil is a supreme source of fat, naturally high in healthy monounsaturated fatty acids (MUFAs), and in beneficial bioactive compounds, including phenolic compounds, phytosterols, tocopherols, and pigments1.

How to choose your Olive Oil?

Olive oil should just be olive oil, plain and clear. Unfortunately, in the United States, labeling regulations allow a product named olive oil to contain other oils blended in it. Therefore, it is important you follow some guidelines and pay attention to certain details to guarantee you are purchasing good quality olive oil.

  1. Extra Virgin Olive Oil (EVOO)

By choosing EVOO, you are already guaranteed to meet some of the best olive oil standards. See Table below, modified from Oliviada Olive,20 highlighting the main differences between Extra Virgin Olive Oil (EVOO) and Regular Olive Oil.

How to Choose the Right Olive Oil
  1. Organic

Organic has several benefits: it is safer because it will have less chemicals; more nutrient dense and rich in bioactive compounds; enhanced flavor and taste due to higher nutritional value; non-GMO (non-genetically modified crops, although so far there are no GMO olives) and will also help preserve our ecosystems and be less pollutant, with more environmental-friendly practices, and less use of pesticides, herbicides, and fertilizers.

  1. Dark Glass Bottle or Other Light Protection

Light protection is critical for the preservation of any oil, and it is especially important for olive oil, since exposure to ultraviolet light is one of the main reasons for oil rancidity. A study published in 2021 used different packaging for storing EVOOs with different phenolic and volatile compound contents, aiming to evaluate the effects on oil quality evolution over 10 months of light exposure21.  It was reported that “packaging material type and initial antioxidant composition significantly influenced EVOOs’ resistance to oxidation, and consequently their quality,” showing that protection from light is paramount for EVOO quality. Interestingly enough, this study concluded that multilayer (plastic-coated paperboard aluminum foil) packaging provided superior protection against oxidation when compared to green glass and ultraviolet-grade absorbing glass21. The EVOOs stored in multilayer containers “retained their characteristics within the regulatory limits and contained more antioxidants and fewer ‘rancid’ defects and related volatile compounds21.”

A 2020 research found that a square dark glass bottle provides the best-combined protection of major secoiridoids from oxidative and hydrolytic degradation and that stainless-steel cans showed the lowest levels of oxidized byproducts (when compared to a ceramic jar and a clear polyethylene terephthalate bottle) 22.

While multilayer containers provide great light protection, we want to avoid both plastics and aluminum in contact with your food, so we would still recommend a dark glass bottle, if possible, with added light protection. Also, by buying a good EVOO, with a rich chemical composition, the negative effects of light exposure on the quality of the olive oil will be reduced21,23.

  1. Store in a Cool, Dark Place

EVOO is a high-quality product with profound health benefits but is susceptible to degradation and oxidation, mainly due to environmental conditions, such as temperature, oxygen, and light, that may promote the oxidative processes24.  Therefore, for better preservation of EVOO qualities, such as antioxidant level and presence and integrity of phenolic compounds, it is essential to store your olive oil at cool temperatures and not be exposed to direct light.

A study published in May 2022 evaluated the phenolic composition of three EVOO samples kept at different storage conditions for 15 months, focusing on the variation of oleocanthalic acid content, a product resulting from oleocanthal oxidation25. In this study, the samples were stored at 4 °C in darkness and at 25 °C with light exposure. The conclusion was that “although chemical-physical characteristics of EVOOs are slightly different depending on provenience and treatment time, the results of this study reveal that storage conditions are fundamental to controlling phenol concentration,” highlighting that due to “the greater influence of external factors on storage conditions,” EVOOs exposed to light and maintained at 25 °C (77 degrees fahrenheit), showed a more marked degradation than EVOO stored in the dark and at 4 °C (39 degrees fahrenheit)25.

Another 2021 study reported that “EVOOs stored under lower temperature conditions were associated with a higher quantity of secoiridoid derivatives and non-oxidized phenolic compounds, indicating that lower storage temperatures limited the oxidation of the oil components.” Basically, this study provides scientific evidence that storage conditions, namely storage temperature, are highly relevant to ensure the quality of EVOO26.

Yet another study found that “the cultivars with a higher concentration of polyphenols showed greater resistance to the formation of oxidation products; an indication that they have a higher thermal stability24.” This means that if you buy a better quality EVOO, with higher concentration of polyphenols, the oil itself will be more resistant to oxidation and degradation, both from light exposure and temperature changes23,24.

Storing in appropriate bottles, in the dark, and at cool temperature is also crucial after opening.

  1. Best Before or Harvest date

Recently produced EVOO, freshly extracted from olives that have just been harvested, is usually a higher quality olive oil, retaining most of its beneficial properties. So, when buying your EVOO look for the harvest date or best-before date.

However, you don’t have to completely reject or disregard oils from a previous harvest because in order to be commercialized as EVOO, a best-before date of up to 24 months is required and EVOO quality is expected to be preserved. This means that the EVOO should retain its chemical properties and preserve its ‘extra virgin’ category within the “best-before” period26.

However, research published in 2021 evaluating the decrease in the phenolic content of 160 EVOOs after 12 months of storage in darkness at 20 °C showed that the phenolic concentration decreased an average of 42.0% (± 24.3%) after the 12-month period. The reduction was also strongly dependent on the initial phenolic profile27

Once again, try to buy a high-quality EVOO, and if the harvest date or “best-before” information is available, a more recent harvest would present a higher phenolic content. Harvest seasons are usually October through January in the Northern Hemisphere and April through June in the Southern Hemisphere.

  1. Consume in a Short Period of Time After Opened

After opening, you should try to consume your olive oil within one to two months. If you think you don’t use it as much, then consider buying smaller bottles. Periodical exposure to oxygen (which happens after opening and during use) was shown to be a very relevant factor for the oxidative degradation of EVOO22. Pay attention to the “Best Before” date, trying to get as far in the future as possible. If your olive oil turns out to be rancid when you open it, return it for a refund28.

  1. Price Matters

When it comes to olive oil, price definitely matters. EVOO, due to all the reasons mentioned above, costs more to produce; hence it is only normal that it costs more to the consumer than low-quality oils. With olive oil, if it’s cheap, it is because it’s probably not a good quality oil. And with any oil, due to the importance of having healthy fats in your diet, the highest quality possible is the healthiest choice possible! Remember, you need healthy fats to build new healthy cells, so buy the best you can find and afford.

  1. Farmers and Producers

It is often a better option to buy from brands that actually make their own olive oil. Even better if the brand owns the olive tree groves and is responsible for all production phases: growth, collection, and selection of olives, milling, and bottling28. This information may be available on the label, or you can even check the brand website and the history behind the product you are buying. When people are directly involved in the whole process, or at least work in direct contact or partnership with farms and millers, quality control tends to be higher, and the olive oil better28

  1. Single Origin

Higher quality EVOO tends to come from a single region. You can find in most grocery stores, single origin EVOO produced in the United States in California and many other single origin EVOO, mostly from European countries. Ideally, the country of origin is displayed on the bottle label (front or back label) and is often stated in abbreviations: IT for Italy, ES for Spain, GR for Greece, PT for Portugal, etc28. When olive oils from multiple origins are used, then the brand is probably just responsible for the packaging and labeling phase of the product and is not responsible for other areas of production28. Read labels and ideally buy single-origin extra virgin olive oil from “farm-to-bottle” brands.

  1. Quality Assurance and Certification Seals

In the United States, there are several quality seals that have varying standards and monitoring practices. Different standards can be tested, mainly related to chemical composition, but there are also trained tasters28, just like with wine. Some of these companies are28:

  • Olive Oil Commission of California (OOCC)
  • North American Olive Oil Association (NAOOA)
  • California Olive Oil Council (COOC)
  • Extra Virgin Alliance (EVA)

There are also the European Union’s “Protected Designation of Origin” programs (PGI, PDO, DO, or AOC), which guarantee that the oil was produced in a specific region using traditional olive varieties28.

How to Choose the Right Olive Oil

11. More Detailed Information

Additional information, even when not legally required, is usually a good sign. This can include farm location, olive varieties, agricultural practices, milling and processing details, etc28.

But do not let yourself be “cheated” by branding and marketing. Certain added information, such as “Non-GMO” or “Vegan,” is not really useful since there are no GMO olive crops, and olive oil uses no animal products.

12. Taste

One of the most important factors is that you actually like and use the EVOO that you are buying. EVOO should taste fresh and fruity, be a little bitter, and be slightly peppery. The flavor profile resembles healthy fresh olives, ripe or green. If it tastes rancid (like stale walnuts), or there are hints of fermentation (similar to fermented feta cheese, or described as “sweaty socks” or too-wet compost), then it is probably not a good quality olive oil, or it was not well processed and stored28.

Are you adding a good extra virgin olive oil to your delicious meals?



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