Composition of the olive oil
Olive oil is composed of substances that come directly from pressing, without undergoing any chemical modification.
Composed almost entirely ( 95-98 %) of triglycerides, which are esters of glycerol with fatty acids : These fatty acids are represented by about 75% monounsaturated fatty acids ( oleic acid with prevalence ),14-16 % of saturated fatty acids ( such as palmitic predominates ) and about 8-9 % from polyunsaturated fatty acids ( with a predominance of small amounts of linolenic acid and linoleic acid).
In addition to these main components, olive oil contains other compounds, present in small quantitiee. These numerous substances (including sterols, aliphatic and triterpene alcohols , polyphenols , tocopherols , aroma components , etc...) Even when present in small amounts ( 0.5-2 %) , have a decisive effect on the nutritional and sensory quality of olive oil , as it is very different from that of all other vegetable oils.
A special mention must be made of two of these substances, polyphenols and tocopherols.
These two classes of compounds are probably the most important among the minor constituents of olive oil, as they are related to aspects that cause the peculiarities of extra virgin olive oil quality and the differentiation between cultivars and different environments where the trees grow.
The reasons for the importance of these two classes of compounds are related to the fact that :
a. they are able to prevent the oxidation reactions of the fatty acids and therefore contribute to the stability of the oil over time , delaying rancidity and the loss of its most valuable sensory characteristics .
b . in the body they are able to prevent and inhibit numerous reactions of free radicals, limiting the formation of free radicals and other abnormal molecules which can alter the normal functioning of the cell membranes and many metabolic processes .
Tocopherols , or vitamin E, are present in virgin olive oil again in a concentration of the order of 150-300 mg / kg, which gradually decrease over time, especially if the oil is stored in open containers and not protected from light.
The concentration of polyphenols depends mainly on the cultivar , the characteristics of land ( soil , elevation , exposure , microclimate , humidity) and the time of harvest: for they are found in higher concentration in green olives, and their content decreases progressively with maturation . The concentration and composition of polyphenols also significantly affect the taste of the oil , contributing to the bitterness and pungency of fresh oils . Their degradation leads to substantial changes in taste , which over time tends to lose the characteristics of fruity and bitter to a more sweet one .
Among the most important polyphenols there is oleoeuropeina , with a distinct bitter note , it degrades into other elements , such as hydroxytyrosol and tyrosol, which don’t have a bitter taste and so explains the change in flavor over time. The oleoeuropeina has nutraceutical and pharmacological properties with a documented coronary - dilating action , hypoglycemic and anticolesterolemica . The other polyphenols have pharmacological and cosmetic properties and are used in products with skin protecting and anti -aging properties .