Estudio de la trazabilidad integral de los aceites de oliva virgen extra de la provincia de Huelva

Resum

The objective of this work is to implement the concept of fully comprehensive traceability in an olive oil producing region by the study of geographical and sensory traceability of extra virgin olive oils from Huelva. Several compounds and elements that form part of the oil are likely to be subjected to a tracking process using various analytical techniques and they may be used as traceability markers. The elemental composition of soils, olive-pomaces and olive oils, as well as the content of fatty acids, sterols, erythrodiol and uvaol, have been chosen as markers for geographical traceability. The phenolic profile and the content of volatile compounds in oil samples, have been selected as markers for sensorial traceability. The elemental composition of soil, olive-pomaces and olive oils has been achieved by the development of acid digestion techniques based on the use of Teflon reactors assisted by microwaves. ICP-MS (inductively coupled plasma-mass spectrometry) has been employed for the determination of major and trace elements in the same types of samples. The correlation between the elemental composition of several soil, olive-pomaces, olive oils samples and their geographical origin has been studied. The coincidence in the selection of the elements for classifying soils (W, Fe, Na), olive-pomace (W, Fe, Na, Mg, Mn, Ca, Ba, Li) and olive oils (W, Fe, Mg, Mn, Ca, Ba, Li, Bi) in accordance with the geographical provenance indicates that some elements present in the soils of the orchards might also be detected in the olives and olive oils, though at much lower concentrations. Therefore, element analysis by ICP in combination to multivariate analysis is a powerful tool for establishing traceability of oil samples. The fatty acids composition has been determined following the method proposed by Annex X of EEC 2568/91 Regulation. Also, the method proposed by Annex V of the EEC / 2568/91 Regulation has been applied for determining the content of sterols, erythrodiol and uvaol. The application of SLDA to the results obtained for the fatty acids and sterols content allowed 93.75% of correct classifications of all of the samples analyzed according to their geographical origin. The content of stearic, gadoleic, behenic, palmitoleic, linolenic and arachidonic acid as well as campesterol and stigmasterol were the variables with greater contribution for the discrimination between groups. When this analysis was applied to Arbequina and Picual samples independently, 100% of correct classifications were obtained. We conclude, therefore, that the content of sterols and fatty acids contributes to the establishment of the geographical traceability of the oil samples studied. A new method for determining the phenolic profile by liquid chromatography with UV diode array detector, using a C18 column Ultrabase 2.5 pm(ioo mm x 4.6 mm internal diameter), has been proposed. Inconclusive results were obtained when a discriminât analysis was applied to the content of phenolic compounds obtained by HPLC-DAD from the oil samples in order to differentiate them according to their origin. Although the mean values of each group were separated along the main canonical function, only 43% of Gibraleon's samples were correctly classified. More information regarding the phenolic composition of the oils was obtained applying the method described by Becerra et al. 2014, for the determination of phenolic compounds by UHPLC- ESI-MS /MS. Also, the volatile compounds in the same established samples were determined by the method described by Tena et al. 2007. The multivariate statistical analysis applied jointly to the data obtained for phenolic and volatile compounds has revealed the potential of these compounds, particularly the volatiles ones, to discriminate the samples according their origin with a 100% of correct classifications, establishing what might be called sensorial traceability.