Chemical Analysis
What determines the quality of olive oil in chemical analysis and what interests us most are:
The acid (acidity)
is an important parameter for assessing the quality of a (native) olive oil. It is the content of free fatty acids in olive oil, produced by the action of the enzyme lipase contained in the fruit. The acidity is given as a percentage.
The factors that negatively affect acidity are:
Overripe or injured olive fruit.
Insect infestation (Dacus) of the olive fruit.
Longer storage of olives after harvest and until oiling.
The lower the acidity, the better the quality of our olive oil and the more bitter and savory its taste will be.
The number of peroxides (quality of life)
Peroxides are chemical compounds that are formed (oxidation) through contact with oxygen (air).
The number of peroxides therefore gives us an indication of whether the olive oil has been exposed to oxidation. Oxidation can be enzymatic (created during olive oil production, by enzymes present in the olive) or chemical (created during olive oil storage after production).
In the case of refined oils, this parameter gives no indication of anything, since during the refining process any product resulting from oxidation is eliminated, and therefore any characteristic that indicates its age.
The factors that negatively affect the number of peroxides are:
Damage to the olive fruit during harvest, storage
The contact of olive oil with waste water
light (sunbeams)
temperature
oxygen
Traces of metallic elements
Κ232 (oxidation)
K232 is the initial or intermediate stage of oxidation. An increased K-232 value indicates increased oxidation processes (e.g. too high temperature or too long storage between harvest and pressing). It tells how the production method and the storage conditions of an olive oil were.
Κ270 (aging)
K270 is an advanced oxidation or refining stage. Oxidation (degradation) occurs over time (i.e. aging). This means that the K-270 value is low for fresh oil and increases with age. A mixture with old oil also results in an increased K-270 value. Poor storage, i.e. under light or at excessively high temperatures, will accelerate aging. So it tells us how fresh an olive oil is. Refined olive oils therefore have a high K270 value.
Delta K ΔΚ (Purity)
The delta K value (ΔΚ) is calculated from the difference between the values K-266, K-270 and K-274 and serves as a comparison value. If there is a difference (delta) here, this indicates a mixture with other oils. Ie the value tells us how pure the olive oil is for its quality class.
Factors that influence this are:
light (sunbeams)
temperature
oxygen
Traces of metallic elements
The values K-232 and K-270 as well as Delta K show how many oxidized components are in the oil and whether the oil is pure or adulterated.
polyphenols
Polyphenols are so-called phytochemicals that give plant foods their color. The most important polyphenol in olives is oleuropein. It is a very good antioxidant, making it a powerful scavenger of free radicals, which can wreak havoc in the body. In addition, they serve the plants as defenses against predators or microbial attack and also act as growth regulators.
The content of phenolic compounds in olive oil depends on the cultivation and degree of ripeness of the olives at harvest. There are also varietal differences.
Polyphenols are therefore a good reason to consume high-quality olive oil. In contrast to vitamins, polyphenols are heat-resistant and remain largely stable, so that high-quality olive oil should also be used for cooking and frying. Good olive oils contain 250 to over 800 mg of polyphenols.
Table with the limits that determine the extra virgin olive oil:
parameter
Extra Virgin Olive Oil
Ultra premium olive oil
acidity (%)
max ≤ 0.8
max ≤ 0.3
Peroxides (meq Oâ‚‚/Kg)
max ≤ 20.0
max ≤ 9.0
Κ232
max ≤ 2.5
max ≤ 2.0
Κ270
max ≤ 0.22
max ≤ 0.20
ΔΚ
max ≤ 0.01
max ≤ 0.01
polyphenols
-
min ≤ 130
Basic principles of tasting