Although the acidity of olive oil is a widely discussed subject, there are many misconceptions about it among both consumers and professionals.
To understand in detail what we are referring to, we at Aceites La Matilla would first like to help you understand where olive oil originates within the olive itself.
How is olive oil formed?
Oil forms naturally inside the olive itself as triglycerides. Each one is a package of three fatty acids joined together by a molecule called glycerol.
However, the bond between the three fatty acids and the glycerol is not very strong, so any change in the environment that can oxidise it causes it to break and release the three fatty acids. In other words, the olive oil degrades.
Olive oil acidity measures the amount of these free fatty acids present in the oil, which is why this parameter is a general indicator of the quality of virgin olive oils.
In short, the lower the acidity of the olive oil, the better.
What is the difference between the flavour of olive oil and its acidity?
The truth is that fatty acids have no taste. Confusing intensity with the acidity of olive oil is therefore a widespread mistake.
The acidity of olive oil cannot be detected by the palate, so linking a sweeter, more bitter, more intense or saltier taste with the acidity of olive oil is completely mistaken.
Much of the blame lies with the industry, which through its labelling linked this acidity to refined olive oil (which has neither flavour nor acidity), when in fact this characteristic applies only to extra virgin olive oil.
Olive oil acidity values by type
The acidity level of olive oil is one of the parameters most widely used to classify the different types of virgin olive oil:
Extra virgin olive oil: its acidity must be less than or equal to 0.8 degrees
Virgin olive oil: its acidity must be less than or equal to 2 degrees
Why is olive oil acidity no longer shown on the label?
Previously, the acidity of olive oil was shown as a quality feature on containers of olive oil, though not on those of virgin olive oil.
However, as this caused confusion among consumers, since it does not necessarily reflect quality, the legislation changed and required producers to provide more information alongside the acidity of olive oil.
For this reason, this index began to be disregarded and producers of virgin olive oil began to use the terms “mild” or “intense” to refer to this element.
How does acidity increase in virgin olive oil?
We have seen that the acidity of olive oil increases when the oil is exposed to oxidising, harsh conditions. Now let us look more closely at how the triglycerides change over the life of olive oil.
In the olive
Whatever the type of olive (Arbequina, Gordal, Hojiblanca…), inside each one the triglycerides are protected from the oxygen in the air by the skin that covers it. If the skin breaks or deteriorates, oxygen gets inside and begins to break down the triglycerides, and the acidity of the final olive oil starts to rise.
An olive can break for many reasons: insect bites, weather conditions or even falling to the ground. In short, olive oil made from healthy, undamaged olives, or from olives freshly picked from the tree, will have low acidity.
During storage, several factors also come into play that affect the level of acidity in olive oil. When the olives reach the mill, they are unloaded into hoppers. There, the olives at the bottom are crushed by the weight of those above them. Oxygen then damages the olives again as their skins deteriorate.
If too much time passes before the olive is processed into virgin olive oil, the acidity level of the oil rises considerably and fermentation may even set in.
This problem is known as olive heating in the hopper (atroje), and it worsens as the olive ripens, since the riper an olive is, the softer it is and the more easily it is crushed.
During olive oil production
Once the olives are at the mill and being processed into olive oil, the paste is exposed to the open air and therefore runs a serious risk of oxidation. The longer the milling process lasts, the greater the oxidation of the virgin olive oil. Temperature plays a key role here: the higher the temperature, the higher the acidity level of the olive oil will be.
During the storage of extra virgin olive oil
Once the extra virgin olive oil is stored in the cellar, it remains at risk of further oxidation. If the tanks are not airtight, or are airtight but not completely full, there will be air at the top.
For this reason, some mills remove this air and introduce nitrogen so that the oil keeps in perfect condition and reaches the highest quality, making it possible to produce oils such as gourmet olive oil.
