Olive Oil Testing

The authenticity and quality of olive oils are determined based on their physicochemical and organoleptic characteristics, as provided for in Regulation (EEC) 2568/91.
In order for these characteristics to be controlled in a uniform manner, the same regulation also establishes the methods of chemical analysis and organoleptic assessment.
The quality of olive oil is significantly degraded even during the fruit development stage upon contact with parasites, microorganisms, moisture, oxygen, intense light, temperature, and is determined by organoleptic assessment (panel test) and by measuring certain physicochemical parameters, such as acidity, peroxide value, absorption coefficients K270/K232/ΔK, etc.

The physicochemical parameters based on which the quality of olive oil is characterized are as follows:

Physicochemical Characteristics of Olive Oil
ACIDITY
Acidity is the most important criterion for the qualitative evaluation of olive oil and determines its commercial value.
The acidity of olive oil is an important parameter and has been established by the European Union that for an oil to be characterized as extra virgin, the acidity must be below 0.8%.
If its value is between 0.8% and 2%, it is characterized as virgin, while for values above 2% it is refined and is not suitable for consumption.
Acidity is related to the products content of oleic acid (grams of free oleic acid/100 grams of fat).
The higher the number, the greater the free fatty acid content of the olive oil and the more its quality is degraded. High acidity usually means that the olive oil comes from damaged olives or unsuitable processing conditions.

PEROXIDES
Peroxides are chemical compounds  formed by the action of oxygen on olive oil. Oxidation can be enzymatic or chemical.

Enzymatic oxidation is caused both by lipases, which are natural enzymes of the olive fruit, and by those enzymes released by various types of microorganisms that develop during the storage of the fruit under unsuitable conditions. When the olive oil is separated in the olive mill, these enzymes are removed with the wastewater, as they are water-soluble proteins. In this way, the olive oil ceases to be subject to the action of these specific enzymes.

Chemical oxidation occurs during the preservation of olive oil, through a mechanism of free radical formation.

Factors affecting the peroxide value
The application of good agricultural practices during cultivation and harvesting, the observance of good storage practices, as well as the application of the rules of good industrial practice throughout the olive oil production process in the olive mill, enables us to produce olive oil with a low peroxide value.

Enzymatic oxidation is caused when the fruit cells have been broken during harvesting and storage, but also during the crushing and grinding of the fruit.

Chemical oxidation is favored by light, high temperature, the presence of oxygen, and metal elements.

High peroxide values indicate that the olive oil has undergone oxidative or other alterations and are associated with a reduction in its shelf life.

Therefore, the determination of the concentration of peroxides allows us to draw conclusions about the age and type of storage of the olive oil.

Based on the aforementioned, it is possible to produce olive oils with a low peroxide value when:

we reduce enzymatic oxidation by applying good practices in the cultivation, harvesting, storage, pressing of the olive fruit, as well as the production of olive oil
we reduce chemical oxidation by protecting the olive oil from light, high temperature, air, and traces of metal elements.

 According to Community Legislation, the peroxide value for standardized olive oil must be:

 less than 20 meqO2 / kg for "extra virgin olive oil" and "virgin olive oil"
                                                                                   less than 15 meqO2 / kg for "olive oil composed of refined olive oils and virgin olive oils"
 In fresh olive oils, the peroxide value is usually less than 10 meqO2 / kg, which indicates that oxidation proceeds slowly when the olive oil is in the fruit.

In refined olive oils, the peroxide value must be less than 5 meqO2 / kg, because they have undergone chemical treatment (refining).

K232

The constant K shows us whether our olive oil has been stored under unsuitable conditions. Also, the K232 coefficient increases the more days it takes for the olive fruit to be transported to the olive mill. Other reasons that affect the K232 coefficient:

-light,
-air,
-the cleanliness of the storage area,
-temperature, and
-the storage material.

K270

On the other hand, the constant K270 shows how fresh the olive oil is and its authenticity.
    Old olive oils or olive oils containing mixtures of old olive oils show increased K270 values, as well as if they have been exposed to light and high temperatures.

ΔK Index

The ΔK index is a criterion for distinguishing the quality and purity of olive oils.
To determine this index, the K270 and K232 values are combined in a physical formula and compared with a value of extra virgin olive oil. The ΔK value can be positive or negative in case of differences.
Practical significance: The Constant shows any mixing with another olive oil that is not "extra virgin".
The ΔK value of extra virgin olive oil should be negative (upper limit 0.01).


With the fatty acid profile, it is possible to determine every fatty acid  contained in the oil and the partial categorization of the oil.  (e.g., cis-trans, Ω3 -Ω6 and others).


The indications written on the packaging of olive oil are defined by Regulation (EC) No. 1019/2002 and concern the retail trade of olive oil sold as a pure product or incorporated into food.
All standardization units are obliged to comply with the marketing specifications referred to in this Regulation, from 1 November 2003 onwards.

Olive oil is among the most popular oils in the world. Its chemical composition consists mainly of triglycerides (~99%) and free fatty acids, sterols, tocopherols, and others.
Its high polyphenol content ranks it among foods with proven antioxidant activity.
According to European Regulation 2568/91, there are specific quality criteria for classifying an olive oil as extra virgin or virgin.
The fatty acid profile usually consists of: (1) Oleic acid (C18:1), 55 to 83%, (2) Linoleic acid (C18:2), 3.5 to 21%, (3) Palmitic acid (C16:0), 7.5 to 20%, (4)  Stearic acid (C18:0), 0.5 to 5%, (5) Linolenic acid (C18:3), less than 1.0%.
The fatty acid profile is a critical parameter for identifying adulteration in olive oils from other types of oils.