The use of objective tests to determine an olive oil´s quality has two purposes. On the one hand, it allows for the comparison of the composition of two apparently similar oils. These tests can also be used to establish the origin and nature of the oil, that is, whether an extra virgin olive oil , refined, pomace oil, or a mixture of oil from other seeds. The analysis that determine an olive oil origin is an area of investigation that is under constant development and whose techniques are becoming increasingly sophisticated.
The following are some of these important olive oil chemical analysis:
The acidity of olive oil is a measure of the fatty acids it contains, commonly expressed in degrees (1º=1%). The acidity for an extra virgin olive oil must be less than 1%.
Generally, the acidity of an olive oil obtained from healthy, ripe olives is very low, ranging from 0.3 to 0.5% and always less than 1%. Olive oil that has an acidity higher than that could mean that there are defects in the oil, which is usually the result of the olives not being pressed quickly enough after collection, the oil being stored at elevated temperatures or being overexposed to light and air during the production process.
However, olive oil with an acidity of less than one percent does not necessarily mean that it is of higher quality, given that the acidity level could be reduced or eliminated in the refining process. In cases such as this, the beneficial components of the oil disappear along with the acidity.
Therefore, it is important to look at other factors, not just the acidity level, when determining the quality of olive oil.
The wax content in a quality olive oil must be less than 250mg. of wax per kilogram of oil. Elevated levels of wax in virgin or refined olive oils are indicative of the presence of crude pomace oil, which is solvent extracted and naturally contains high levels of wax.
The peroxide level indicates the presence of natural antioxidants in virgin olive oils. When an olive oil is deteriorated at some point in its production process, these antioxidants are destroyed. Peroxide tests shed light on the possible evolution of the oil, even when unpleasant odors and flavors are present.
Quality olive oils should generally have a peroxide level of less than twenty, although it is possible for very deteriorated oils to have low levels as well.
K-232 and K-270
These tests are based on the use of ultraviolet rays of 232 and 270 nanometers. They measure the purity of olive oil, as the results in refined oils are higher than those of virgin olive oils. If the presence of fatty acids from oil other than olive oil exists, the results will also increase, which is why this test is used to detect mixes with other olive oils.