Analysis of the influence of multiple parameters on the commercial categories of Extremadura virgin olive oils

Although Extremadura is an important producing region of Spanish virgin olive oils, it has not been always known for the high quality of its oils. However, implementation of continuous extraction systems in most of its olive mills has shown a general improvement in the quality of most virgin olive oils, but not in all of them. The aim of the present study was to examine how different variables, such as fruit quality discrimination or payment system, affected the overall quality of virgin olive oils from Extremadura. To do so, a screening experimental design and the corresponding statistical analysis of the collected data were performed. Sixty Extremadura oil mills were evaluated (50.4% of the total) by taking bottled virgin olive oil samples from each of them. Statistical relationships between physicochemical parameters and production process variables were evaluated, showing that only three of them (separation of ground- and tree-harvested fruits, differential payment according to acidity, and extraction process) were significantly correlated with the quality index and acidity of virgin olive oils.