Interactions Between Hammer Mill Crushing Variables and Malaxation Time During Continuous Olive Oil Extraction

Abstract

Hammer mill crushing variables and malaxation time are studied through a two-level factor factorial experimental design in order to assess the impact of these parameters and their interactions on olive oil extraction efficiency, overall quality, and minor components composition. Extraction efficiency is mainly affected by the interaction between hammer mill grid size and malaxation time; higher yields are obtained when smaller grid sizes are combined with longer malaxation times. Regarding quality parameters and volatile compounds, the main effect is caused by malaxation time. Phenolic compounds are affected by all the studied parameters, hammer mill grid size has the highest impact on their final concentration in the oil. The results show that the effect of malaxation time on the studied variables is conditioned by the crushing parameters used during paste preparation. Practical Applications: Traditionally, the impact of processing variables on olive oil composition has been studied following a one-variable-at-a-time approach. A factor factorial experimental design allows the interactions among crushing conditions and malaxation time to be determined, as well as the individual contributions to extraction efficiency and minor components composition of these variables. Considering a more holistic approach to the study of olive oil extraction might provide processors with a wider spectrum of tools to maximize both yield and quality during olive oil processing. Interaction of grid size, rotor speed, and malaxation time during olive oil extraction affects extraction efficiency, volatiles, and phenolics.