Surface-Enhanced Raman Spectroscopy for Monitoring Extravirgin Olive Oil Bioactive Components

Abstract

Olive oil is the main fat source of the Mediterranean diet. This seasoning ingredient is highly appreciated for its unique taste, functional properties, and positive impact on human health. The determination of chemical composition is a demanding task in order to fully characterize this precious food product, ensure its quality, and prevent fraudulent practices. Among innovative techniques proposed for the oil analysis, surface-enhanced Raman spectroscopy (SERS) can be an extremely useful tool for olive oil characterization. In this frame, we have investigated five noncommercial olive oils produced in different parts of South Italy by using a commercial Raman microspectroscopy apparatus and home-made signal-enhancing SERS substrates. A wavelet-based data analysis has allowed us to efficiently remove the background and the noise from the acquired spectra. The analysis of these SERS spectra has enabled the quantification of the relative contents of carotene, oleic acid, and phenols. These relative contents differ in the examined samples. In addition, SERS response in the lipid region has indicated differences in the relative abundance of saturated fatty acids. The present results confirm the validity of the SERS technique as a rapid, nondestructive, and reliable analytical technique for identifying olive oil bioactive components.

Application of Raman Spectroscopy to Evaluate the Structure Changes of Lubricating Grease Modified with Montmorillonite after Tribological Tests

“…The intensity level of the characteristic bands (1658 cm −1 and 1440 cm −1 ) in the tested vegetable greases with linseed oil as the main component of the composition was changed, which proves that the mechanical forces to which the grease was subjected during the extortions in the tribological system had a significant importance for the evaluation quality of the grease after the tribological tests and may indicate unfavourable changes in the properties of the grease and its further suitability for lubrication purposes. The obtained results and their analysis, as well as the results presented by other scientists [65,66], show that Raman spectroscopy is a fast and effective technique for assessing the quality of vegetable lubricants.…”

“…Raman spectroscopy is a technique that enables the evaluation of changes in the chemical composition of vegetable oils by analysing the degree of unsaturation of fatty acids in vegetable oils, which makes it a very good diagnostic and quality control method for lubricants based on vegetable oils [63][64][65], including linseed oil, which was used by the author of this publication to prepare vegetable lubricant compositions that were subjected to tribological tests. On the basis of the publications of other authors, it was possible to obtain information allowing the quality of vegetable lubricants subjected to tribological tests to be evaluated.…”

Importance of some minor compounds in olive oil authenticity and quality

“…Several recent reviews and studies in the literature provide information regarding the current regulations about olive oil as well as their methods of analysis (Bajoub, Bendini, Fernández-Gutiérrez, & Carrasco-Pancorbo, 2018;Conte et al, 2019;Tena et al, 2015). Some novel techniques (Surface-enhanced Raman spectroscopy (SERS), biosensors, microfluidic devices) have also been applied in olive oil authentication (Bremer, Smits, & Haasnoot, 2009;Deng et al, 2018;Du et al, 2019;McIntosh et al, 2016) and in determination of some bioactive compounds of olive oils especially polyphenolic content (Al Mughairy, Al-Lawati, & Suliman, 2019;Camerlingo, Portaccio, Delfino, & Lepore, 2019;Hammami, Kuliček, & Raouafi, 2016;Ramos, Contreras, & Macías, 2020). Some well-known minor compounds such as sterols, stigmastadienes, aliphatic hydrocarbons and phenolic compounds along with major compounds (triacylglycerols, fatty acid contents) which have official limits in regulations were evaluated in detail in the previous reviews (Aparicio, Conte, & Fiebig, 2013;Arvanitoyannis & Vlachos, 2007;Ben-Ayed, Kamoun-Grati, & Rebai, 2013;Boskou, 2008;García González et al, 2018;Montealegre, Alegre, & García-Ruiz, 2010) Olive oil is very rich in terms of phenolic compounds such as hydroxytyrosol, tyrosol and oleuropein.…”

Resonant Raman Spectroscopy of Carotenoids in Aging of Extra Virgin Olive Oil

“…Surface-enhanced RS (SERS) was used in conjunction with wavelet analysis to extract the Raman signal from the very strong fluorescence background in the Raman window of a 633 nm excitation [9]. Other studies have cited 633 nm as the worst excitation for fluorescence suppression [10].…”