From the orchard to the virgin olive oil quality: a critical overview.

Nowadays the extra virgin olive oil (EVOO) marketable quality includes parameters describing the alteration state and assuring the oil genuineness, but it does not consider markers for the EVOO health and sensory quality. With regard to health aspects, mono-unsaturated fatty acids and hydrophilic phenols are the most important compounds characterizing the EVOO health properties, whereas volatile and phenolic substances can be considered impact components of the EVOO sensory quality. EVOO natural antioxidants include not only hydrophilic phenols but also tocopherols and carotenoids. Secoiridoids are exclusive of EVOO, furthermore they are the main phenols associated to the EVOO health proprieties. They also confer bitter and pungency EVOO taste sensory notes. The EVOO volatile compounds responsible for its typical flavour (i.e., "cut grass", "floral") are C5 and C6 saturated and unsaturated aldehydes, alcohols and esters. The concentrations of phenolic and volatile compounds and monounsaturated fatty acids in the EVOO, are strongly affected by several agronomic and technological conditions of its production. Cultivar, ripening stage of the fruit and cultural practices, such as irrigation, are the main agronomic factors affecting EVOO fatty acids, phenolic and volatile compositions with a significant impact on the sensory and the health quality. Among technological factors, crushing and malaxation are the critical points of the EVOO extraction, because of their influence on hydrophilic phenols and volatiles content. The crushers, destoner included, have shown differentiated effects on oxidoreductases activity and consequently on EVOO phenolic (polyphenoloxidases and peroxidases oxidize polyphenols) and volatile composition (lypoxigenase pathway produces C6 and C5 aldehydes, alcohols and esters) as well as, time, temperature and oxygen concentration during the malaxation. Besides new EVOO extraction technologies are also oriented to increase the value of their by-products with the use of animal feeds based on stoned pomaces for improving the sheep milk quality and the recovery of bioactive phenols from vegetation waters for producing functional foods among others.