Fluorescence spectroscopy for monitoring extra virgin olive oil deterioration upon heating

Abstract

Fluorescence spectroscopy is a reliable and fast method for determining the deterioration of extra virgin olive oil (EVOO). EVOO was analysed by HPLC for determining antioxidant changes in EVOO due to heating at 170°C for 3 h. This thermal oxidation caused a significant exponential decrease in hydroxytyrosol (OH-Tyr) and vitamin E (vitE), while the reduction in the tyrosol content was relatively small. Hydroperoxydes were analysed by an indirect colorimetric method. Their content decreased exponentially during the heating process. Fluorescence excitation spectra with emission wavelength at 330 nm were recorded to monitor the evolution of polyphenols and vitE, while fluorescence excitation spectra with emission at 450 nm were used to monitor the evolution of hydroperoxydes. Results of partial least-square calibration models (PLS) show that the degradation of polyphenols, vitE and hydroperoxide, as well as formation of fluorescent components derivatives can be quantified with fluorescence spectroscopy. Application of chemometrical data analysis allows to optimise the extraction of the information contained in the data. Fluorescence can therefore be used as a rapid technique for evaluating the quality of heat-treated EVOO.

Fluorescence spectroscopy and chemometrics in the food classification - a review

“…Fluorescence spectrometry and PLSR can be used as a rapid technique for evaluating the quality of heat-treated extra virgin olive (Cheikhousman et al 2004) and rapeseed oils (Mas et al 2004).…”

Front Face Fluorescence Spectroscopy Combined with PLS‐DA Allows to Monitor Chemical Changes of Edible Vegetable Oils during Storage at 60 °C

“…The negative peak at 288 nm should correspond to polyphenols. [18,46] Moreover, it is also worthy to note that the dispersion of capped and uncapped LO samples in their group (cluster) appears to follow a tendency in accordance with the evolution of the storage time. No difference was noticed between capped and uncapped samples.…”

“…Although the excitation fluorescence spectra of RO and SO did not provide a maximum fluorescence intensity at this wavelength, they exhibited a shoulder corresponding to the development of new fluorescent components related to the degradation of hydroperoxides products. [ 46 ] Indeed, aldehydes and polymers of certain components, which fluoresce at this wavelength of excitation, could derive from hydroperoxide. From these observations, it can be concluded that the shape of these fluorescence excitation spectra could be considered as fingerprints allowing the differentiation between the four oil types.…”

“…Previous research works reported a tight correlation between fluorescence spectra and hydroperoxide content. For instance, Cheikhousman et al, [18,46] mentioned that increases of the oil fluorescence spectra intensity were inversely correlated with the hydroperoxide content of EVOO before and during 60-130-160, and 190 min heat treatment at 170°C. The fluorophores generated throughout heating may correspond to degradation products of hydroperoxides.…”

Deterioration of Extra Virgin Olive Oil Caused by Different Processes

“…As most of these bioactive compounds (including phenolic compounds) are gradually lost there are no differences in behavior between the different grades of olive oil. In addition, the polyphenols content is affected by the thermal process, but their loss depends on their molecular structure (Gómez-Alonso et al, 2003;Carrasco-Pancorbo et al, 2007;Cheikhousman et al, 2005;Daskalaki et al, 2009;Romero et al, 2003).…”