Wine has a strong importance for many countries all over the world especially in international trade. Numerous criminal attempts were made to undermine established methods in wine controlling and to increase the amount of wine sold by stretching it with low-grade qualities. It is of great economic importance to guarantee that the wine origins from the declared region or that the wine is not blended or adulterated. In order to constrain the origin of wine a set of legally established analyses are made. However many of these can only provide ambiguous results.
So far only concentration profiles of different elements are used to constrain the origin of wine. The concentration of Strontium e.g. in wine has been measured and published (compilation in Horn et al., 1992) and varies between 57 ppb and 7 ppm depending on its origin. One common method for discriminating wines by their geographical origin is measuring stable isotopes (18O/16O, 13C/12C, H/D). The disadvantage of this technique is the sensibility of these elements for mass fractionation in geological and biological cycles and the high expense in the measuring technique.
The strontium-isotopes in wine as fingerprint for its origin has been used first by Peter Horn in 1992. By nutrient transfer from soil to plant the isotopic composition of Sr should not be changed and the wine and soil are expected to have identical isotopic composition. The Sr-isotopes are a powerful tool because the measured accuracy outranges the expected Sr variation by far.
We chose for this first study four typical soils in the region Rheinland-Pfalz from different sites (Weinanbaugebieten) composed of different geological units varying in their Sr-isotopes: 1. Quaternary Löß, 2. Permian Sandstone, 3. Devonian quartzite, 4. Tertiary Rupelton. To check the homogeneity of the soil, 4 to 6 aliquots of each vineyard were sampled, discriminated in different soil horizons having different significance for the roots of the plant.
A first attempt was to measure the Sr isotope ratio of soil and corresponding wine to evaluate our hypothesis. In a next step the transfer of Sr from soil via plant to wine has to be constraint. It includes the analyses of fertilizers, vine, leaves, grapes, juice and all the materials which interact with wine during its production (e.g. Chalk, Silica).
Horn, P., Schaaf, P., Holbach, B., Hölzl, S. & Eschnauer, H. Z., Lebensm. Unters. Forsch. 196, 407-409 (1993).