RADIOGENIC ISOTOPE COMPOSITIONS OF WINE AND PROVENANCE SOIL AS POTENTIAL FINGERPRINTS OF GEOGRAPHIC ORIGIN

The size and scope of wine fraud has grown in recent years with an increasing number of counterfeit and adulterated wines being confiscated by law enforcement agencies such as the FBI and Scotland Yard. This is true not only for wines of premium vintages but also for modestly priced varieties. Wine fraud not only represents a loss of millions of dollars for the wine industry but also defrauds and can potentially pose a health hazard to the consumer. As such, the problem of wine fraud has necessitated the use of analytical methods to determine the origin in which the wine was grown and thus substantiate authenticity and ascertain fraud.

The use of radiogenic isotopes of certain elements, e.g., Sr, Pb and Nd, has been well established in numerous studies as a geochemical tool for dating and tracing the origin of rocks and minerals. This study adapts the analytical principles used in determining the origin of igneous rocks by applying the radiogenic isotopes of Sr, Pb and Nd to determine a wine’s origin. The reason for choosing radiogenic isotopes of Sr, Pb and Nd for this study is based on the assumption that the isotope composition of wine reflects that of the soil upon which the grape vine is grown and are characteristic of the geographical origin of the wine. Therefore, grapes grown in different regions will have different compositions of these isotopes. Isotopes of Sr, Pb and Nd in soils depend on the elemental ratios Rb/Sr, U-Th/Pb, Sm/Nd, respectively, and the geologic age of the rocks upon which the soils developed. Furthermore, since Sr, Pb and Nd are heavy elements, the isotope composition remains unchanged during their incorporation into a plant from the soil. Therefore, the Sr, Pb and Nd isotopic composition of the soil will be consistent with those of the grapes and wines, thus serving as a potential geochemical fingerprint to verify a wine’s authenticity. As a result of this project, a methodology suitable for the determination, by thermal ionization mass spectrometry, of radiogenic isotope ratios of Sr, Pb and Nd in wines and their respective soil, grapes and vines, with sufficient precision that will allow for the distinguishing of wines from different regions.