A general method is described for the identification of paraffin- and silicone-based surface treatments applied to single-piece natural and 1 + 1 (cork agglomerate with two natural cork disks) cork stoppers used to seal wine bottles. The method is based on Fourier transformed infrared spectroscopy (FTIR) and attenuated total reflectance (ATR) analysis of ready-for-use stoppers. The absorbance in seven wavelength bands selected as the most characteristic (2916 and 2850 cm(-)(1), for paraffins, and 2963, 1258, 1079, 1010, and 787 cm(-)(1), for silicones) was measured for both kinds of stoppers. Univariate analysis of the results enabled identification of stoppers that had received surface treatment by measuring the absorbance in two of the selected bands, representing paraffins and silicones, respectively. The type of surface treatment used was identified by discriminant analysis. Using this technique, we constructed a mathematical model using the seven bands studied. The model correctly classified 100% of the stoppers used to construct it and 91.7% of the stoppers used for validation.

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<p style="text-align: justify;"><strong>Aims</strong>: To provide a better knowledge of cork-wine interaction, focussing on absorption of liquid by the cork stopper and overall migration of non-volatile compounds from the cork-stopper to liquid.</p><p style="text-align: justify;"><strong>Methods and results</strong>: Natural cork stoppers and 1+1 technical cork stoppers (agglomerate cork body ended with natural cork washers), with and without surface treatment, were used to close bottles filled with 12 % v/v ethanolic solution and removed after 3, 6, 12 and 24 months of contact. Mean and limit values of absorption and overall migration at each time are used to compare treated and non-treated stoppers. Variation of absorption with contact time was studied by adjusting the ABSORPTION = a · Ãt model (R2: 0.8572 - 0.9756).</p><p style="text-align: justify;"><strong>Conclusion</strong>: Most of the overall migration is due to natural components of cork. Contact time and type of cork stopper are the factors responsible for the greatest variability. Surface treatment increases overall migration (2 mg/stopper) and reduces liquid absorption (more than 10 %).</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: The results show how a correct characterization of stopper and surface treatment is needed to predict the evolution of cork-wine interaction.</p>

Cork is used in enology due to the unique physicalmechanical and chemical properties of the material including impermeability and mechanical behavior. These properties guarantee the maintenance of liquid tightness for prolonged periods of time, as well as a minimal cork-wine interaction (Maga and Puech, 2005;Silva et al., 2005). Despite its low intensity, the influence of this interaction on the evolution of bottled wine is outstanding, as shown by the numerous studies published on the transfer and absorption of volatile compounds by cork stoppers and the effect of the stopper system on wine micro-oxygenation (Juanola et al., 2005;Lopes et al., 2005;Skouroumounis et al., 2005).This work is focused on a less studied aspect: absorption of liquids by the cork stopper. The interest in the absorption phenomenon is due to the fact that it notably AbstractTo evaluate the magnitude of wine absorption by cork under conditions as close to reality as possible and its evolution in time, ready-to-use natural cork stoppers and "1+1" cork stoppers were used to close bottles filled with red wine. Stoppers were removed after 3, 6, 12 and 24 months of contact to determine absorption of liquid and liquid progression along the lateral surface of the cork stopper. Variation of absorption with contact time was studied by adjusting the model Absorption = a t (R 2 : 82.19 -93.63%). A scheme of the evolution of wine absorption with time is proposed, differentiating liquid flow along cork-glass interface, diffusion in cell walls and liquid flow through the cell lumens. In conditions of use, a value of 4.48·10 -13 m 2 s -1 was obtained for non-radial diffusion coefficient (D).Additional key words: cork-wine interaction, diffusion, natural cork stopper, technical cork stopper. Resumen Absorción de vino por los tapones de corchoEl objetivo del presente trabajo fue evaluar la magnitud de la absorción de vino por el corcho en condiciones reales y su evolución con el tiempo. Para ello, se utilizaron tapones de corcho acabados, naturales y "1+1" para cerrar botellas de vino tinto. Los tapones fueron extraídos después de 3, 6, 12 y 24 meses de contacto con el vino y se determinó la absorción y la progresión del líquido por la superficie lateral del tapón. Para estudiar la variación de la absorción con el tiempo, se ajustaron modelos del tipo Absorción = a t (R 2 : 82,19 -93,63%). Se presenta un esquema de esta evolución, diferenciando el flujo de líquido a lo largo de la superficie corcho-vidrio, la difusión en las paredes celulares y el flujo de líquido a través del lumen de las células de corcho, obteniéndose un valor de 4,48·10 -13 m 2 s -1 para el coeficiente de difusión en dirección no radial para el corcho en condiciones de uso.Palabras clave adicionales: difusión, interacción corcho-vino, tapón de corcho natural, tapón de corcho técnico.Abbreviations used: CETIE (Centre Technique International de l'Embouteillage et du Conditionnement), RH (relative humidity), SE