Is unfiltered olive oil better than filtered? Check their science-backed differences regarding their appearance, taste, health benefits, shelf life and more.
You're in the grocery store trying to find a bottle of olive oil for this Greek salad (horiatiki) and then you see it. There's a bottle saying unfiltered extra virgin olive oil and another one that says filtered.
You're confused. What's the difference between the two? And which one is better?
High quality extra virgin olive oil (EVOO) is one of the main ingredients of the Mediterranean Diet and has been used in the Mediterranean cuisine since the ancient times.
It contains plenty of monounsaturated fatty acids, which are considered to be a healthy form of fat, as well as antioxidants and other compounds beneficial for the human body.
The quality and flavor of olive oil depends on the type of olives used, the growing conditions (soil, climate, etc) and the method of production.
The olive oil production process includes the collection of the olives from the olive trees, washing and pressing of the olives, followed by the malaxation of the resulting olive paste.
This thick paste undergoes centrifugation, decantation and (most of the times) storage. Before bottling, the olive oil can undergo filtration or be bottled unfiltered.
Filtration is used for the removal of suspended solids (olive fruit particles) and moisture. But is it good for the olive oil?
Main differences - Which is better?
The main difference between filtered and unfiltered extra virgin olive oil is the presence of sediment or small olive fruit particles in the unfiltered oil.
Unfortunately, there is no definitive answer regarding which is better, since many of the studies are controversial.
However, "better" can be objective, so the following comparison between the characteristics of these two types of olive oil will help you decide for yourself.
Filtered olive oil is clear and transparent, while the unfiltered version has a cloudy appearance and can form sediment at the bottom of the bottle.
The sediment is formed by the tiny particles of olive fruit which are suspended in unfiltered olive oil, and because of gravity, they fall to the bottom of the bottle with time.
Unfiltered olive oil generally has stronger, more robust flavor and fruity aroma. Both types have peppery notes and you may also feel a slight burn at the back of your throat.
Nutritional value - health benefits
Unfiltered olive oil may contain more nutrients, such as antioxidants and other beneficial compounds. However, the difference in nutrient content between filtered and unfiltered olive oil is typically minimal.
Filtered olive oil is best for cooking (has a higher smoke point) and baking (milder flavor and a smooth texture).
Unfiltered is best for dipping, salads, and as a finishing oil because of its rich, fruity flavor and because its nutrients can be destroyed in high temperatures.
As mentioned below, research is controversial regarding the stability and quality of unfiltered and filtered virgin olive oil.
However, the majority of experts and producers seem to agree that filtered olive oil generally has a longer shelf life because the filtering process removes any impurities that could cause the oil to spoil more quickly.
Storage and shelf life
Olive oil should be stored in dark glass bottles and kept in a cool, dark place in order to be protected from oxidation caused by heat and light.
The bottle should also be tightly sealed, otherwise it can go rancid faster. Ideally, it should be consumed within the first 18-24 months after production, but if you want to ensure maximum flavor and freshness you should use it within the first 6-8 months.
Olive oil older than 2 years has probably has lost some of its health benefits, but consuming it doesn't oppose any risks.
Olio nuovo (first harvest)
Olio nuovo which means "new oil" is an Italian term used to describe the firsts harvest (new) extra virgin olive oil. In Greece olio nuovo is called "agourelaio" which means "unripe oil" and is considered to be the top quality, premium oil.
This type of oil has intense fruity flavor with a slight bitterness and peppery finish, deep bright green color, and high nutritional content. Olio nuovo is produced from the first, greenish colored olives, immediately after they are picked, without any processing or filtering.
This results in an extra virgin olive oil (evoo) packed with polyphenols and health antioxidants up to 5x the antioxidant content of most other extra virgin olive oils.
To enjoy all the health benefits of this first harvest oil, you should preferably consume it within 6 months of production.
This is because from the moment an olive is pressed, the oil begins to decay by losing its polyphenol content. The appearance of sediment and a slight change of color after a few months are normal.
This type of oil is best used raw as a finishing oil or drizzled over salads and vegetables. Though you can also cook with it, this is generally not advised because of it strong flavor and because the heat can destroy some of its nutrients.
According to oliveoil.com, after the extraction process most olive oil is filtered (run through cellulose pads or diatomaceous earth) and/or racked (allowed to rest so the sediment settles on the bottom of the tank) to remove bioactive particles like remaining olive particles, or residual amounts of water.
Decanting: This is the most basic filtering method and involves simply letting the oil sit in a container until any sediment settles at the bottom, then pouring off the clear oil on top. This is the method many olive oil producers follow for their household oil.
Gravity filtration: The oil passes through a series of filters that remove sediment and other impurities. Gravity filtration can be done using a variety of materials, such as paper, cotton, or polypropylene.
Centrifugal filtration: As the name suggests, a high-speed centrifuge is used to separate the oil from any sediment or water particles. The disadvantage of this method is that it can remove some of the oil's flavor.
Pressure filtration: This method uses pressure to force the oil through a series of filters such as diatomaceous earth, activated carbon, or cellulose pads.
Studies on filtering effects
According to this study on the effects of filtration "results showed that filtration and dehydration delayed the appearance of rancid defects. The formation of simple phenols due to the hydrolysis rate of their secoiridoid derivatives was also greater in unfiltered olive oils.
Thus, filtration and especially dehydration could help to prolong the shelf life of high-quality and less stable olive.
Also, in the article filtered or unfiltered olive oil from oliveoiltimes.com, it is mentioned that the International Olive Council (IOC), the intergovernmental organization of olive oil-producing nations, recommends that olive oil undergo filtration to remove any solid microparticles and water, increasing the oil’s shelf life.
In another article regarding the question if unfiltered olive oil is healthier, it is mentioned that the olive particles in unfiltered olive oil will continue to ferment in the bottle, thus accelerating the oxidation of the oil.
On the other hand, in this study about the influence of filtration on olive oil quality during storage, it is recommended that the filtration step should not be done for keeping the olive oil quality and its oxidative stability.
In this study about the effects of filtration process in the stability of extra virgin olive oil it is concluded that:
"the suspended materials contain chemical compounds that act as antioxidants; the elimination of the ﬁltration step is therefore highly desirable to extend the shelf life of the oil.
Moreover, phenolic compounds are a powerful antioxidant more protective against oxidation in a water-in-oil emulsion, but the ﬁltration system reduces the water content.
As a consequence, unﬁltered olive oils may be more stable. However, the higher polar phase content in unﬁltered olive oils may augment alteration of virgin olive oil, although only after several months of storage.
We can conclude that, the filtration procedure, as a final step, is especially important to the quality of EVOO and the consumer acceptance".
Reading the rest of the study it is concluded that the oxidative stability is better in unfiltered olive oil throughout the first months of production, but in the long term, filtered oil demonstrates better ability to keep its characteristics unaltered.
Extra virgin olive oil (evoo): The highest quality and most flavorful type, made from the cold pressing of the olives with acidity level less than 0.8%. It can be filtered or unfiltered.
Virgin olive oil: Similar to evoo but with higher acidity level, up to 2%.
Pure olive oil: A blend of virgin and refined olive oil.
Light olive oil: A highly refined olive oil.
Cold-pressed olive oil: Made without heat or chemicals, thus preserving the natural flavor and nutrients of the olives.
Organic olive oil: Made from olives grown without the use of synthetic pesticides or fertilizers.
- Unfiltered extra virgin olive oil has more antioxidants and more robust flavor, but you should buy it as fresh as possible and consume it quickly after opening (ideally within the first 6 months).
- Filtered extra virgin olive oil remains one of the higher quality oils (almost as much as the unfiltered) and has a longer shelf life and should be consumed within 2 years from production, and ideally within the first 12 months.
- If the label doesn't say extra virgin olive oil, then it is probably a filtered, refined olive oil blended with a very small quantity of virgin olive oil.
Additional sources: olivenews.gr (in Greek)