The organoleptic assessment of olive oil depends to the human senses and the color, taste and aroma are the main characteristics used to determine the quality of the virgin olive oil. The organoleptic assessment is used because it is the most effective method to assess the qualitative differences between olive oils, differences that physicochemical analysis fails to identify.
Color: The color is associated with the quality of the oil and this one at extra virgin olive oil is between light yellow and green, depending on the conciseness of chlorophyll and carotene in olive. Chlorophylls are responsible for the yellow-green color, while carotene gives color between yellow and red. The level of these substances is associated with genetic factors, production conditions and the stage of ripening of the olives. The concentration decreases with maturation and disappears with full maturity of the olives.Should be noted that the organoleptic assessments that have been developed for the assessment of the virgin olive oil does not require the determination of the color, as this measurement is done using special instruments.
Taste: The taste is the sensation perceived when the taste receptors are stimulated. The four basic tastes are sweet, salty, sour and bitter. Virgin olive oil does not contain sugar or salt, and the sense of sour, due to the free fatty acids, is not perceived, because they are not soluble in the body temperature. The bitterness in virgin olive oil is due to compounds found in olives, the glycosides. They include substances such as tyrosol and hydroxytyrosol, responsible for its bitter taste. The proportion of these compounds in olive oil depends on genetic factors, the ripening of olives and the technological processes of olive oil extraction. The concentration increases during maturation, reaching a maximum gain when the olive have purple coloration.
Those oils extracted in metal mills are bitter than those from stone mills. The long time kneading and the high temperatures reduce the bitterness. Similarly, extraction by pressure or centrifugal biphasic system produce olive oil with intense bitterness. Glycosides are responsible for the astringent taste of some virgin olive oils. Their presence creates a feeling of dryness in the mouth and unripe taste, such as the taste that wines or quinces might have. Moreover, they are increasing the feeling of hot in some oils.
Aroma: The aroma of the virgin olive oil is the sum of perceived sensations, generated when the different chemical compounds, which are transported with the air during the inhalation and exhalation, reach the olfaction receptors. The taste is produced from volatile low molecular weight chemical compounds. The stimulus can be perceived directly, when the aroma reaches through the nose the olfaction receptors and indirectly , when the aroma is being volatile at body temperature, passes through the mouth to the olfactory epithelium.
Over one hundred volatile chemical compounds identified in virgin olive oil which contribute to make an unforgettable aroma, which include C6 alcohols, aldehydes and esters. None of these chemical compounds can not explain alone the overall feel of the aroma that extra virgin olive oil gives.
The ripening stage during harvesting affects the taste of the olive oil. The maximum aroma intensity corresponds to the maximum content of volatile substances at the optimum ripeness. The system of the oil extraction and the conditions during the processing – especially during the grinding and kneading of the olives- affect the type and the intensity of the aroma. Intense grinding and prolonged kneading at high temperatures adversely affect the aroma of the olive oil. However, pressure or centrifugal biphasic system produces olive oil with intense aroma.