Fluorescence spectroscopy in monitoring of extra virgin olive oil during storage

The present study demonstrates the use of fluorescence spectroscopy for monitoring changes in virgin olive oil during storage. Total luminescence and synchronous scanning fluorescence spectroscopy techniques were tested with the purpose to check their ability to monitor changes occurring in olive oil during storage in different conditions: in clear and green glass bottles exposed to light, and in darkness. Total luminescence spectra of the initial oil samples in n-hexane solutions exhibited intense peaks, one with a maximum appearing at 320 nm in emission and 290 nm in excitation, attributed to tocopherols, and another appearing at 670 nm in emission and 405 nm in excitation, belonging to the pigments of the chlorophyll group. The intensity of these emissions decreased during storage depending on the storage conditions. Additional bands appeared in oils exposed to light in the intermediate range of excitation and emission wavelengths, arising from unidentified compounds. Bands attributed to tocopherols, chlorophylls and those tentatively ascribed to phenolic compounds were observed in the synchronous scanning fluorescence spectra, allowing monitoring of the storage effects on these constituents and their quantitative assessment after appropriate calibration. The results presented confirm the capability of the fluorescence techniques to monitor the quality of oil products.