Verification of the age of 10- and 20-year-old Tawny Port wines using Radiocarbon

Port is a famous sort of fortified wine, exclusively produced in the Douro region of Portugal. Among the various types of Port wines, the Tawny types with stated maturation ages of 10 or 20 years are among the higher quality and more expensive ones. Fraudulently producing those with a shorter maturation time than claimed, along with additions or treatments to mask this, would make production of those wines cheaper. Here, we present a method, based on Radiocarbon (¹⁴C) age determination of the ethanol and the sugar residue, to verify the maturation time of such Port wines. We successfully verified the method using single harvest year “Vintage” Port wines. We then analyzed a total of twenty 10- and 20-year-old Tawny Port wines, bought at various retail stores in the Netherlands. We found that seven of those had a significantly shorter maturation age than claimed on the label.