Analytical Methods Raman spectroscopy of white wines Coralie Martin a,b , Jean-Luc Bruneel a , François Guyon c , Bernard Médina c , Michael Jourdes d,e , Pierre-Louis Teissedre d,e , François Guillaume a,⇑ a Université de Bordeaux, CNRS, ISM UMR 5255, 351 cours de la Libération, F-33405 Talence Cedex, France b Advanced Track and Trace, ATT 99 avenue de la châtaigneraie, F-92500 Rueil Malmaison, France c Service Commun des Laboratoires, 3 Avenue du Dr A. Schweitzer, F-33608 Pessac, France d Université de Bordeaux, ISVV, EA4577 Unité de Recherche Oenologie, F-33140 Villenave D’ornon, France e INRA, ISVV, USC 1366 Œnologie, F-33140 Villenave d’Ornon, France article info Article history: Received 24 July 2014 Received in revised form 15 January 2015 Accepted 14 February 2015 Available online 20 February 2015 Keywords: Raman spectroscopy Fluorescence spectroscopy White wines Phenolic composition Hydroxycinnamic acids Sugars abstract The feasibility of exploiting Raman scattering to analyze white wines has been investigated using 3 dif- ferent wavelengths of the incoming laser radiation in the near-UV (325 nm), visible (532 nm) and near infrared (785 nm). To help in the interpretation of the Raman spectra, the absorption properties in the UV–visible range of two wine samples as well as their laser induced fluorescence have also been inves- tigated. Thanks to the strong intensity enhancement of the Raman scattered light due to electronic reso- nance with 325 nm laser excitation, hydroxycinnamic acids may be detected and analyzed selectively. Fructose and glucose may also be easily detected below ca. 1000 cm À1 . This feasibility study demon- strates the potential of the Raman spectroscopic technique for the analysis of white wines. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction Analytical methods are essential tools for wine quality control and authentication. Among all spectroscopy techniques currently used in this context, often complementary, there is a great need for low cost analytical tools that are small and light enough to be handled for field analysis. Optical methods based on the phe- nomenon of light absorption have experienced significant develop- ments in recent years for the characterization of wines. These methods encompass absorption spectroscopy in the mid-infrared (MIR) and the near-infrared (NIR) for studying fundamental mole- cular vibrations and their harmonics (Bauer et al., 2008; Cozzolino, Dambergs, Janik, Cynkar, & Gishen, 2006; Cozzolino, McCarthy, & Bartowsky, 2012), absorption spectroscopy in the ultra-violet and visible (UV–vis) for probing electronic transitions (Acevedo, Jiménez, Maldonado, Domínguez, & Narváez, 2007; García-Jares & Médina, 1995; Harbertson & Spayd, 2006; Roig & Thomas, 2003; Urbano, Luque de Castro, Pérez, García-Olmo, & Gómez-Nieto, 2006). These techniques are well suited in an industrial context due to their ease of use, their measurement quickness, their relatively low financial cost and also because they can be small enough (miniaturized in a near future) for in situ operation. Surprisingly there has been very little research carried out on wines by means of spectroscopic techniques analyzing the emission of light. Indeed for wavelengths of light in the 260–1100 nm range, several phenomena will take place involving the electronic polar- ization of the molecules. Let us consider the interaction of a monochromatic electromagnetic radiation (laser) with molecules. If there is no absorption of the incoming radiation, elastic (Rayleigh) and inelastic (Raman) scattering of photons will occur. The spectral analysis of the Raman scattering provides information on molecular vibrations (Raman scattering effect is fully described in many books, see for instance (Dietzek, Cialla, Schmitt, & Popp, 2010)). If now the molecule absorbs the exciting radiation, two phenomena involving different mechanisms may take place if we exclude phos- phorescence. The first one is fluorescence (Lakowicz, 2006) and the second is resonance Raman scattering (Dietzek et al., 2010). The resonance Raman spectrum will display maxima at the same posi- tions to that of normal Raman scattering, but the vibrations coupled to the absorbing functional groups may be strongly intensified. To the best of our knowledge, only one paper has been pub- lished so far about Raman scattering of white wines (Meneghini et al., 2008) and none about resonance Raman scattering. A very few studies based on front face fluorescence spectroscopy for direct and global analyzes of wines have already been published (Airado-Rodríguez, Durán-Merás, Galeano-Díaz, & Wold, 2011; Dufour, Letort, Laguet, Lebecque, & Serra, 2006; Le Moigne et al., http://dx.doi.org/10.1016/j.foodchem.2015.02.076 0308-8146/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Fax: +33 (0)5 4000 3183. E-mail address: f.guillaume@ism.u-bordeaux1.fr (F. Guillaume). Food Chemistry 181 (2015) 235–240 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem