The Effect of Diverse Agricultural and Technological Factors on Olive Oil Quality and Yield.

The quality of extra virgin olive oil (EVOO) can be determined thanks to the use of some parameters whose values can be used to evaluate the healthy and sensory properties of oils. Actually, the marketable quality is defined by analytical parameters evaluating the state of alteration and ensuring the genuineness of the oil. On the other hand, important markers defining the healthy and sensory quality of oil are not considered for evaluating oil quality. In particular, the most important markers that determine the healthy quality of EVOO are the monounsaturated fatty acids content and the natural antioxidants amount, while volatile and phenolic compounds can be considered as components affecting the EVOO sensory properties. Hydrophilic phenols are the most abundant natural antioxidants of EVOO which also contains tocopherols and carotenoids. The main classes of EVOO hydrophilic phenols are phenolic alcohols, lignans and secoiridoids. EVOO secoiridoids are the main phenols associated to health properties and, at the same time, they are responsible for the bitter and pungency sensory notes of EVOO. High contents of secoiridoids (derivatives of oleuropein, demethyloleuropein and ligstroside) can be also found in the by-products of oil mechanical extraction process such as vegetation waters and pomaces. The volatile compounds that are responsible for EVOO flavour are produced by the lipoxygenase pathway (LOX) which catalyses the genesis of C-5 and C-6 saturated and unsaturated aldehydes, alcohols and esters. These compounds are correlated to the "cut grass" and "floral" sensory notes of EVOO. The concentration of phenols, volatile compounds and monounsaturated fatty acid in the EVOO is strongly affected by agronomic factors and technological operative conditions of oil extraction process. With respect to the technological aspects the processing parameters such as crushing and malaxation operative conditions and extraction system are of great importance in the determination of the oil hydrophilic phenol content and in the volatile formation by LOX pathway. In fact, different types of crushers have different effects in the PPO POD and LOX activation and, therefore, affect the phenolic concentrations and volatile composition of EVOO. Moreover, the malaxation conditions (time, temperature and oxygen concentration of pastes) regulate the activity of the above mentioned enzymes with a strong influence on the final concentration of hydrophilic phenols as well as on the C-5 and C-6 saturated and unsaturated aldehydes, alcohols and esters composition of EVOO. In this respect, the control of oxygen during malaxation represents a new technological parameter that can be adopted to optimize the phenolic concentration in the oil. The new technologies in oil mechanical extraction process are also oriented towards the valorisation of olive by-products (stoned olive pomaces and vegetation waters). In fact, the stoned pomaces used for the animal feeding (cows and water buffalos) to improve the quality and oxidative stability of milk and cheese have been studied as new approach the pomaces valorisation. The vegetation waters utilization can be related to the recovery of hydrophilic phenols with high biological activities that can be applied to produce functional food enriched in antioxidants.