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The acidity of olive oil is a subject as widespread as misinterpreted by consumers and even by cookers. We will try to clarify some doubts.
Index
The oil is naturally generated within the olive fruit forming triglycerides. Each triglyceride is a package made up of three fatty acids linked by a molecule called glycerol.
The link between glycerol with the three fatty acids is weak, so before any aggressive or oxidizing atmosphere, it breaks and set free the three fatty acids, and consequently the olive oil starts degrading. Acidity measures how much of these free fatty acids are in the olive oil; therefore acidity is a general indicator of the quality of virgin olive oils.
Acidity, the parameter written at the labels of the bottles, measures the amount of free fatty oleic acid, the most abundant in the olive oils. Acidity is the rate in weight of the free oleic acid over the total amount of olive oil. In the labels it should be written in percent (%), but for some reason that we do not know this rate has always been expressed as degrees (°).
Among consumers there exist a certain confusion about the acidity of the olive oil. Almost everybody tend to confuse it with the intensity of the flavor of the oil, independently whether these flavors are pleasant or unpleasant. In fact, the fatty acids have no taste. We think that the confusion is due to two reasons:
1.- Because they confuse acidity with one of the basic tastes: sweet, salty, acid (sour) and bitter. In reality, they are not related, and acidity, as a parameter of quality, cannot be detected by tasting.
2.- Because, although considering acidity a parameter of quality only applicable to Virgin Olive Oils, the industry has used it in the past on the labels of the 'olive oils', which are mixtures of refined Olive Oils with Virgin ones. So, the more refined oil has an Olive Oil, the less acidity and taste, since refined olive oils don´t have neither flavor nor acidity.
The acidity level is one of the main parameters to classify the quality of the different types in virgin olive oils:
Extra virgin olive oil: Its acidity level must be less than or equal to 0,8º.
Virgin olive oil: Its acidity should be less than or equal to 2º.
All virgin oils with acidity levels over 2º are classified as lampantes.
At the end of the harvest every year, we perform the acidity analysis to our olive oils.
Arbequina, Picual and Hojiblanca olive oils are usually below 0.20 degrees of acidity. (The lowest acidity we have ever got is 0.14º).
Frantoio and Manzanillo olive oils are usually between 0.4 and 0.6º . All of them below the Extra Virgin limit of 0.8 degrees.
You can see the acidity of our olive oils on the analytical page.
Some time ago in the olive oil packagings, not in Virgin olive oil, the levels in acidity of the olive oil appeared as the main claim of their quality.
Since acidity caused confusion in consumers and did not necessarily responded to a quality criterion in olive oils, the legislation changed and currently, and if the producer wish to include the acidity of their olive oils, he must also include other quality values such as the index of peroxides, waxes, and ultraviolet absorbances (K270, K232 and ΔK).
That did not lead the producers to include these additional quality parameters, but rather to eliminate the acidity of the labels and replace them with generic numbers at the beginning, 0.4 and 1, and later by the "intense" and "soft" ratings.
Only in high quality extra virgin olive oils the producers print in their labels the acidity level and other values like peroxides, waxes and the absorbances K.
As we have seen, acidity of an Olive Oil increases as it is exposed to oxidants and aggressive environments. We are going to see how triglycerides, which are the main compound of olive oil, can be broken down along the life of the olive oil.
1.- The Olive Oil inside the olive fruit.
Al first, triglycerides are protected inside the olive fruit against the oxygen in the atmosphere by the skin of the fruit. If the skin is broken, the oxygen gets into the fruit and starts to break down triglycerides and acidity rises. The skin can break down for many reasons: by the bite of pests, by hailstorms, by falling to the ground, because it is crushed in the transportation, etc. In conclusion, the olive oils from healthy olives, without having being bitted and nearly harvested from the tree will have a low acidity.
Another delicate step is the storage of the olives before its grinding. When the olives arrive at the mill are discharged into metallic deposits. There the olives laid in the bottom part are crushed by the weight of the above, with what the oxygen starts to attack. If the olives are deposited a lot of time in these metallic deposits before grinding, the acidity rises significantly and may even start the fermentation process. This problem is increased by the maturity of the olive, as it is much softer and more easily to be crushed.
2. The grinding and production process.
In the mill and when the olives are under the production process, the resulting pulp is in contact with the air and therefore it is exposed to oxidation. The longer the milling process, the more will be oxidized the pulp of the olive fruit. In this case the temperature is important. The higher the temperature, the faster the oxidation reactions, and consequently, acidity will rise. (More over olive oil production).
3.- Storage and conservation in the Olive Oil cellar.
Once produced the olive oil and stored in the cellar, the product could continue its oxidation. In case that the deposits are not watertight, or even being watertight, if the tank is not completely full of Olive Oil, there will be air inside the tank. Some mills removed this air filling it with nitrogen to keep the Olive Oil perfectly.