Medida de diferentes parámetros físico-químicos de aceitunas y aceites vírgenes de las variedades principales cultivadas en Extremadura y desarrollo de Técnicas Elaiotécnicas para la mejora de la comerciabilidad de los Aceites de Oliva Vírgenes

Resum

This doctoral thesis aims to support the olive sector of the Extremadura region by improving the quality and profitability of the extraction processes and thus, increase the industrial performance and reduce the possible devaluation of the oils related to post-harvest conservation times. Virgin Olive Oils of the main varieties grown in Extremadura: Arbequina, Cornicabra, Manzanilla Cacereña, Manzanilla de Sevilla, Morisca, Pico Limón, Picual and Verdial de Badajoz, have been characterized in order to show the singularities of each variety. Singularities that could be used to add value and market differentiation to the oils extracted in the Extremadura region. Different aspects with influence in the quality of the final product like the ripeness index, the epidermis colour or the fruit firmness have been analysed. In the same manner, different techniques affecting the extraction process such as the use of vacuum pulses or the employment of different water qualities during the malaxing stage, as well as the partial reduction of pits after milling, have been tested. In addition and for the first time according to the literature review conducted, this thesis proposes the employment of the olive paste pH measurement as a valid tool to carry out varietal characterization and fruit quality differentiation. In particular and in relation to the latter, the pH measurement has been used to distinguish between batches of fruits harvested from the tree and those batches including fruits collected from the ground. It has been proved that the pH of an olive paste is related to the concentration of total phenols, ortho-diphenols and derivatives Secoiroideos found in its final oil. This fact has been corroborated from the data regarding content of phenols in oils found in oils extracted using water with pH ranging from 4.5 to 9.5