Development of a prototype malaxer to investigate the influence of oxygen on extra-virgin olive oil quality and yield, to define a new design of machine

•Quality and yield of the olive oil is affected by O2 concentration during malaxation.•A control system to monitoring O2 present in head space of a malaxer was developed.•A range of O2 concentration for oil quality and yield extraction was determinated.•The experimental data obtained will be used to design an optimised malaxation machine.

The malaxation has been a focus of extra-virgin olive oil (EVOO) research for many years. A system that supplied gas and measured oxygen concentration was implemented on a prototype malaxer that was used as a control tool to investigate the influence of oxygen concentration on the final quality and extraction yield of EVOO. The oxygen content in the headspace and olive paste was measured and the balance between these contents was assessed; a high correlation between the oxygen consumed in the headspace and the oxygen consumed by the olive paste was found. The optimal amount of oxygen per kilogram of dough over 40 min of kneading was identified to be in the range 55.4–77.9 mg [O2] kg−1 [olive paste]. This oxygen content facilitates the acquisition of the best qualitative and quantitative performance during the malaxation process. These data allowed us to define new basic parameters for the malaxer design and to optimise the extraction performance, thus ensuring the production of high-quality olive oil.