Front-Face Fluorescence Combined with Second-Order Multiway Classification, Based on Polyphenol and Chlorophyll Compounds, for Virgin Olive Oil Monitoring Under Different Photo- and Thermal-Oxidation Procedures

Room temperature excitation-emission matrices (EEMs), recorded using front-face fluorescence spectroscopy, and combined with second-order multiway classification methods, were explored as potential tools for controlling the storage conditions of extra virgin olive oil samples (EVOO). Factors such as UV-irradiation, sunlight exposition and temperature up to 80 °C were studied. For each sample, EEMs were obtained in two spectral regions, corresponding to polyphenols, and chlorophyll and derivatives, respectively. The full fluorescence information of excitation-emission matrices was processed with parallel factor analysis (PARAFAC) and PARAFAC supervised by linear discriminant analysis (LDA). The models allowed the discrimination between non-irradiated and irradiated EVOO samples, in both spectral regions. With a temperature of 80 °C, and a heating time of 30 min, the formation of secondary oxidation products was appreciable. In these conditions, the first component of PARAFAC showed a remarkable modification in its profile and LDA-PARAFAC allowed the discrimination between non-heated and heated EVOO samples.