A rapid method to authenticate vegetable oils through surface-enhanced Raman scattering

Abstract

Vegetable oils are essential in our daily diet. Among various vegetable oils, the major difference lies in the composition of fatty acids, including unsaturated fatty acids (USFA) and saturated fatty acids (SFA). USFA include oleic acid (OA), linoleic acid (LA), and α-linolenic acid (ALA), while SFA are mainly palmitic acid (PA). In this study, the most typical and abundant USFA present with PA in vegetable oils were quantified. More importantly, certain proportional relationships between the integrated intensities of peaks centered at 1656 cm−1 (S1656) in the surface-enhanced Raman scattering spectra of different USFA were confirmed. Therefore, the LA or ALA content could be converted into an equivalent virtual OA content enabling the characterization of the USFA content in vegetable oils using the equivalent total OA content. In combination with the S1656 of pure OA and using peanut, sesame, and soybean oils as examples, the ranges of S1656 corresponding to the National Standards of China were established to allow the rapid authentication of vegetable oils. Gas chromatograph-mass spectrometer analyses verified the accuracy of the method, with relative errors of less than 5%. Moreover, this method can be extended to other detection fields, such as diseases.

Micromorphological and anatomical characteristics of Salvia amplexicaulis Lam., S. jurisicii Košanin and S. ringens Sibth. & Sm. (Lamiaceae)

“…Furthermore, there are strong vibrations at 1266 cm −1 assigned to C-H bending deformation. The bands at 1305 and 1443 cm −1 attributed to CH 2 deformations and the CH 2 scissoring mode have also a significant intensity, and the bands at 838 and 866 cm −1 were assigned to C-C stretching (Machado et al 2012;Lv et al 2016), all above mentioned responsible for α-linolenic and linoleic fatty acids. Composition of fatty acids in nutlets indicated the presence of linoleic, but also α-linolenic acid with specific band at 1006 cm −1 (Fig.…”

“…86) contained predominant bands of unsaturated fatty acids. The molecular formulas of α-linolenic and linoleic fatty acids are extremely simple containing only CH 2 , CH 3 , and COOH as functional groups and C-C, C=C, C-H, O=C, C-O, and O-H as chemical bonds, in a case of α-linolenic and linoleic acids there are three or two C=C bonds, respectively (Lv et al 2016). Because these acids differ manly in the position of the double bonds, their Raman spectra are highly similar (De Gelder et al 2007).…”

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

“…Recently, SERS has shown to offer good potentiality for EVOO adulteration detection [27,28] and authentication [29]. Some of us have recently performed a preliminary investigation on Italian EVOOs [30], obtaining promising results about the usefulness of the approach.…”

Calibrated Optical Markers to Study Thermal Degradation in Edible Oils Using Raman and Optical Transmission Spectroscopy

“…The C=C bonds are prone to dissociation resulting in harmful free radicals, ultimately degrading the edible oils. 11,24 However, each individual oil has different contents of C–C and C=C bonds. Hence, in our analysis, we would normalize the changes in the Raman peak intensities that change with respect to the ones that are fairly stable, with thermal oxidation.…”

“…In comparison, Raman spectroscopy, a qualitative technique, has been used to study oils, but is limited by its low scattering cross-section. 22–24 To promote it as an alternative and facile methodology to study thermally stressed edible oils, it has to be correlated vis-à-vis a quantifiable parameter and then calibrated. This can be done through “iodine value”, 25,26 or “bromine value”, 27 which is defined as the mass of iodine/bromine, in grams, to react with 100 g of a chemical and is a measure of the degree of unsaturation in FAs present in edible oils.…”