What does it really mean that an olive oil is "unfiltered"?

What is unfiltered oil?

The definition we found on the internet is: an unfiltered olive oil is one that has not gone through a filtration system to remove impurities and particles that make the appearance of the bottle cloudy and undefined. A "cloudy" oil also known as "crude oil". 

We also read: "Unfiltered olive oil is a product made from freshly pressed olives that has not undergone the filtering process to remove impurities".

But is this really the case, and are all the primary elements retained in olive oil as implied? Not really. All oils, all oils, have a minimum filtration for consumption. For example, decanting is an essential part of the process in the production of any extra virgin olive oil and this already implies a separation of elements.

This first decantation is already a "first filtration", so that the denser elements go down to the bottom of the container, leaving the oil at the top. In fact, in this part of the process we can already speak of "oil" and not "mass". This decantation goes unnoticed in the collective imagination when we speak of "unfiltered" oil.

Before the oil goes into the tanks, it is time to decide whether or not to apply cellulose filtration, which is how we do it.

If you decide "not to filter" the oil, you will keep a small part of the total polyphenols, which would be lost in the filtration. Some of the olive moisture, pulp and other elements would also be retained in the juice.

Why do consumers ask for unfiltered oil?

Mainly because of the belief that the purity of unfiltered oil will result in more flavour, aromas and organoleptic characteristics. But in reality, those of us who are trained and have a tradition of tasting know that the difference between one oil and another is minimal. For example, most of the polyphenols are retained whether filtered or not. In the loss of properties and aromas, the temperature of extraction, which should always be at 27 degrees or less, and the fact that the harvest is later, are more important. These factors are more decisive in an extra virgin olive oil.

The density of the product is not synonymous with a more aromatic or "spicy" taste. In fact, when we are asked for unfiltered oil "with lees", customers do not realise that these lees are, per se, a natural filtration process. In this way, they are getting a product more similar to the original filtered product (made before entering the tanks) than to the unfiltered EVOO that we serve during the first months.

¿Cómo trabajamos nosotros la filtración del aceite?

At Aceites La Muralla we are committed to an unfiltered extra virgin olive oil in the arbequina variety.

Our extra virgin olive oil arbequina variety is presented unfiltered the first months of harvesting and filtered the rest of the months. Why do we present it this way? 

As we have already mentioned, an unfiltered extra virgin olive oil contains moisture from the olives, sugars and other microorganisms that can deteriorate it over time. In fact, although imperceptible to our taste and smell, this deterioration gives rise to what is known in chemistry as pestiferous substances. And this has nothing to do with the correct preservation of the oil. A good tank will optimally protect its contents, but nature cannot be fought against, and the slightest oxidation and oxygenation will cause a gradual and inevitable deterioration. 

For this reason, in order to have a good EVOO from early harvesting and cold extraction, with all its properties for a longer period of time, we prefer to offer it unfiltered only during the first months of the campaign. This guarantees all its properties even if the extra virgin olive oil is consumed in summer, for example. 

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