Innovation in extraction technology for improved virgin olive oil quality and by-product valorisation.

The mechanical oil-extraction process affects sensory and health-beneficial properties of virgin olive oil (VOO), as it is directly related to the generation of volatile compounds and the release of phenolic antioxidants in the oil, which greatly affect VOO quality. Hydrophilic phenols are the most abundant natural antioxidants in VOO. Oil quality is strictly related to the biological activities of these hydrophilic phenols, which affect not only its shelf life but also its health-beneficial and sensorial properties. The prevalent classes of VOO hydrophilic phenols are phenolic alcohols, lignans and secoiridoids. The secoiridoids, derivatives of oleuropein, demethyloleuropein and ligustroside, can be also found in high amounts in the by-products of the mechanical oil-extraction process - the vegetation water and pomace. The volatile compounds, responsible for VOO flavour, are produced by the lipoxygenase pathway which catalyses the genesis of C5 and C6 saturated and unsaturated aldehydes, alcohols and esters. These compounds are correlated to the "cut grass" and "floral" sensory notes of VOO. The concentrations of hydrophilic phenols in VOO and in its by-products and the volatile compounds in the VOO are strongly affected by the operational conditions of mechanical oil-extraction processes. In this context, new approaches to VOO extraction should have the following targets: optimizing the processing conditions to improve VOO's health-beneficial and sensorial properties; valorisation of the by-products (stoned olive pomace and vegetation water).