Chemical profiling of red wines using surface-enhanced Raman spectroscopy (SERS)
In this study, we explored surface-enhanced Raman spectroscopy (SERS) for analyzing red wine through several facile sample preparations. These approaches involved the direct analysis of red wine with Raman spectroscopy, the direct incubation of red wine with silver nanoparticles (i.e., AgNPs), and a reproducible SERS substrate, AgNPs mirror, previously developed by our group. However, as previously reported for red wine analysis, the signals obtained through these approaches were either interfered by the fluorescence contributed by pigments or mainly contributed from a DNA fraction, adenine. Therefore, an innovative approach was developed using solvent extraction to provide more characteristic information that is beneficial for wine chemical profiling and discrimination. Signature peaks in wine extract spectra were found to match condensed tannin, resveratrol, anthocyanins, gallic acid, and catechin, which suggested SERS combining with extraction to be an innovative method in profiling wine chemicals and to overcome well-known challenges in red wine analysis. Based on these approaches, we have successfully differentiated three red wines and demonstrated the possible relation between the overall intensity of wine spectra with the ratings. Since the wine chemical profile is closely related to the grape species, wine quality, and wine authentication, the SERS approaches to obtain rich spectral information from the red wine could advance the wine chemical analysis.