An oxygen monitoring and control system inside a malaxation machine to improve extra virgin olive oil quality

In recent years, oxygen content regulation during malaxation has been noted as a process parameter. The aim of this study was to identify the optimal time during the malaxation process of the olives of the Sicilian cultivar Nocellara del Belice when the presence of oxygen in the machine headspace activates the enzyme complex in favour of the volatile compounds, without compromising the phenolic composition. During the malaxation process, the atmosphere inside the malaxation machine was modified by blowing pure oxygen from cylinders at specific stages of the process (i.e., 5, 15, 25, and 35 min after the start of malaxation), using a system that allows the automatic and continuous maintenance of a known amount of oxygen in the headspace at a given moment during the entire process of malaxation. The results showed that under the experimental boundary conditions, malaxation carried out in an oxygen free atmosphere for the first 25 min followed by the presence of oxygen until the end of the process could enhance volatile compounds in extra virgin olive oils, without compromising the phenolic composition.