Developing nondestructive sensitive detection for smoke-exposure assessment in wine via advanced Raman spectroscopy.

Wildfire smoke has become an increasing problem due to climate change and global warming, and rapid smoke analysis is vital for the wine industry. This work demonstrates a new approach for determining volatile phenol (guaiacol) in wine via surface-enhanced Raman spectroscopy (SERS) and femtosecond stimulated Raman spectroscopy (FSRS). The results showed that several marker bands become particularly enhanced, enabling the detection of guaiacol at lower concentrations than spontaneous Raman. Aided by quantum calculations, band assignments help to elucidate key vibrational motions being enhanced. Furthermore, SERS strips with gold nanoparticles achieved guaiacol detection at the parts-per-billion (μg/L) level in synthetic wine, but at a higher level (mg/L) in authentic wine. Various methods were evaluated to eliminate interference in red wine, where the LiChrolut-EN resin-packed column with dichloromethane eluent achieved the lowest guaiacol detection. We envision future research exploring more effective eluting solvents for solid-phase extraction to maximize volatile phenol retention with simultaneous removal of interfering compounds, together with the optimized SERS/FSRS conditions, could lead to breakthroughs for rapid, sensitive, and nondestructive evaluation for smoke exposure in wine.