Sorption and diffusion properties of volatile phenols into cork

The sorption and diffusion properties of seven common volatile phenols in hydro-alcoholic medium placed in contact with natural cork were investigated to determine the influence of cork closures on the concentration of these compounds in wine. Weighted cork samples were immersed in model wine solutions containing selected concentrations of each compound and were sampled over time. Sorption coefficients ranged between 125 and 306 mg of aroma compound per kg of cork, while diffusion coefficients varied from 0.8 to 4.1 × 10−11 m2/s. Sorption isotherms of guaiacol and 4-propylguaiacol, respectively, the lowest and highest sorbed compounds of an homologous series of guaiacol, accurately fit Henry’s model. Hydrophobicity of aroma compounds seems to be a determining factor in both diffusion and sorption. This could indicate a preferential pathway for diffusion through suberin, the more hydrophobic constituent of cork.