One of the most important characteristics of the olive oil -that the consumer pays most attention to- is the color. Chlorophylls and carotenoids are the two main ingredients, responsible for the color of olive oil, which varies, from yellowish green to greenish gold, and also play an important role on the acidity of the extra virgin olive oil.
The most important factor for the evaluation of the quality of fruits and vegetables is the ripeness, which is determined from the color of the skin.
During the ripening the chlorophyll’s presence (in all unripe fruits and vegetables) breaks down and changes from chloroplasts to chromoplasts.
The olive fruit is a green, fleshy, edible drupe. During the ripening process, the photosynthetic activity decreases along with the decrease of chlorophylls and carotenoids.
At the last stage of ripeness the dark color of the olive fruit is owed to the formation of anthocyanins, which are water-soluble pigments that appear blue, purple or red. They are in the class of molecules that called flavonoids.
When the harvest period starts, the olive fruit is green, turning to light green, the chlorophylls a and b are the main pigments and are decreasing with the process. The decrease of the chlorophylls is more than the decrease in the carotenoid pigments and both end in similar results at the last of the ripening period, the black stage.
The changes in the olive fruit during ripening are reflected in the pigment composition of the extra virgin olive oil. Inside the fruit tissue, olive components as pigments are very staple. The olive oil comes from the olive fruit, and goes through these processess: Crushing, malaxation, extraction and decanting. At the end of the extraction process, a big portion of the chlorophylls and carotenoids are transferred to the olive oil.
With the ripeness of the olives, the concentration of pigments of the oils, diminishes. When the color of the olives turn redish, the content of carotenoids in the oil is higher than chlorophylls.
The quality of the virgin olive oil is strictly related to the phenolic and volatile compounds. The phenolic compounds are responsible for the bitter and pungent taste of the oil and effects its self life.