Chemical changes of thermoxidized virgin olive oil determined by excitation-emission fluorescence spectroscopy (EEFS)

The fluorophores present in virgin olive oil evolve during any thermoxidation process and thereby fluorescence spectroscopy can be used as a straightforward approach to study the oxidative degree of oils. Samples of heated virgin olive oils collected from a fryer every two hours up to 94 h were analyzed to study their excitation-emission matrix (EEM) and the evolution of the fluorescent composition during the thermoxidation process. The potential usefulness of EEM to study thermoxidized virgin olive oils has been explored. For this purpose, parallel factor analysis (PARAFAC) was used to interpret the results. The emission profile obtained from three-factor PARAFAC model calculated for 47 samples of thermoxidized oil in the range of λex = 250-298 nm and λem = 300-700 nm allows the decomposition of the fluorescence landscape in specific information about phenols, pigments and oxidation products respectively. The chemical interpretation from the PARAFAC model was checked with chemical analysis of phenols, tocopherols and chlorophyll pigments.

► A virgin olive oil has been thermoxidized during 94 h at 190 °C to obtain 48 samples. ► The changes in the chemical composition were predicted by fluorescence spectroscopy. ► PARAFAC has been used to study the results. ► Chemical analyzes were carried out to interpret the results from fluorescence spectroscopy.