The geographic origin of wine matters a lot in certain circles. To verify the authenticity of wines produced within their borders, some countries have adopted strict Appellation Control laws to ensure a wine’s terroir. But how can the authenticity of a wine’s geographic origin actually be measured? Enter the chemists. In a new study, researchers say the solution lies in looking at the rocks that lie beneath those succulent grapes. The isotopic compositions of inorganic heavy elements in rocks, such as strontium and neodymium are often used to determine the age and origin of a given rock. The method is foolproof as no two rocks share the same isotopic composition unless they were generated in the same environment at the same time – i.e., they’re the same rock. Because plants that grow on those rocks acquire the same isotopic composition as their host, the grapes in the wines should bear the same isotopic signature as the soil they grew on. Based on that reasoning, researchers looked at strontium isotopes in 45 bottled wines from four regions of Italy. They then compared those isotopic values to the rocks in the wine’s stated birthplace. They also looked at a wine’s isotopic consistency across vintage years. Only two wines showed inconsistencies. In one case, the researchers learned that the winemaker in question started a new vineyard in 2010. While the new vineyard overlay sedimentary rocks, the original vineyard overlay pyroclastic rocks from the Colli Albani volcano. The new vineyard has a substratum made up by sedimentary rocks, whereas the original vineyard of grapes of the 2003, 2005, and 2006 vintages has a substratum made up by pyroclastic rocks of the Colli Albani volcano – which was consistent with the researchers’ findings. In the latter case, winemakers likely added bentonite or limestone silt to the winemaking process, a common practice for white wines. That suggests that the method may be limited to red wines.
Posted on: Thu, 11 Jul 2013 03:20:34 +0000
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