Influenza delle condizioni operative di gramolatura sulla qualità dell'olio extra vergine di oliva

The quality of extra virgin olive oil can be evaluated not only by estimating its product parameters, determined by current regulations in force, but also by assessing its volatile and phenolic compound content. The quantity and types of volatile and phenolic compounds contained in extra virgin olive oil is dependent upon both chemical composition of processed olives and operating condition for processing in olive oil mill. The aim of this work was to investigate how malaxing operating conditions could be able to influence characteristics of extra virgin olive oil. During 2007 crop season, some trials were carried out applying two alternative malaxations: one under oxidative conditions (i.e. using a horizontal-axis, open malaxator), the other under low oxidative conditions (i.e. using a vacuum vertical-axis malaxator). Results showed different effects of oxidative stress impact conditions on total secoiridoid and volatile compounds contents. a lower oxidative stress impact allows oil to be obtained, which is richer in total secoiridoid content, but has a lower volatile compounds content. Trials also showed that a high malaxing time has a positive effect on the total secoiridoid content, when oxidative stress impact is reduced, and that malaxing time only has a positive effect on the volatile compounds content when malaxing is performed in the presence of oxygen. Research showed that malaxing operation does have a significant impact on quality characteristics OF extra virgin olive oil, provided the large number of enzyme activities for transforma- tion of the lipid component of olive paste can be kept under control by a conscious, careful selection of operating conditions.