Stable isotope ratio analysis for verifying the authenticity of balsamic and wine vinegar

According to the law, wine vinegar comes from the fermentation of fresh grape or must. Vinegar cannot contain acetic acid obtained by synthesis or from the fermentation of beet and cane sugar and cannot come from dried grapes diluted with water (the so-called ‘raisin vinegar’ produced in some Mediterranean countries). This is also valid for PGI Balsamic vinegar from Modena, a salad dressing today renowned all over the world, obtained by mixing wine vinegar and grape must. In the case of wine, since 1991 the fraudulent addition of water, cane and beet sugar has been detected by analysing D/H and 13C/12C in ethanol and 18O/16O in water and by comparing the results with those in an official databank. In the case of vinegar, studies about the application of these techniques to balsamic vinegar and an official vinegar databank are lacking. In this work we investigated whether the analysis of stable isotope ratios D/H and 13C/12C in ethanol and acetic acid and of 18O/16O in water can be applied to the ingredients of ABM to evaluate their authenticity. We found that impurities in the extraction solution do not affect the 13C/12C of acetic acid, nor are the D/H values of acetic acid affected under a composite NMR experiment. The sr and sR are comparable in wine vinegar and ABM and generally lower than those quoted in the official methods. This means that the validation parameters quoted in the official methods can also be applied to the ingredients of ABM. In addition, we found no changes in the isotopic values from wine to vinegar and to ABM, and from the original must to the ABM must, providing experimental evidence that reference data from wine databanks can also be used to evaluate the authenticity of vinegar and ABM.