Direct non-invasive molecular analysis of packaging label to assist wine-bottle authentication
Résumé
Alcoholic beverages, especially great wines and spirits, are prime targets for counterfeiters. The simplest form of wine fraud involves fixing counterfeit labels of expensive wines to bottles of less expensive wine. However, time-consuming analytical techniques requiring liquid sampling are mainly used for authentication purposes, which irremediably degrade the value of the bottle. This work aims to develop a new diagnostic tool based on the direct analysis of label matrix and ink in order to obtain valuable information that would enable a preliminary non-destructive authentication. Raman and infrared spectroscopies have been applied for fast, reproducible and discernible molecular characterization since both analytical techniques are strictly non-invasive and do not require sample preparation. They were successfully applied to a selected number of genuine and counterfeited bottles (Pauillac, France) and a series of bottles which goes from 1969 to 2010 belonging to the same producer (Pomerol, France). Raman spectroscopy and infrared spectroscopy showed a great complementarity to clarify the molecular composition of label and inks. As a general overview, pigments are not useful for discrimination purpose in the pairs of original and counterfeited samples. However, several mismatch in label composition were identified, allowing the differentiation among samples. With respect to the second batch of bottles, Raman spectroscopy was able to trace the materials used in labels and inks, giving evidences about the chronologic order of manufacture. Despite the limited number of samples, mainly due to their uniqueness, the classification power of the proposed methodology has been clearly proven.