Use of IRMS and NMR techniques for authenticating grape musts used in the vinegar industry

Aceto Balsamico di Modena (ABM) and balsamic seasonings are among the most valuable Italian food products. The production of ABM is strictly regulated by European regulation (No. 583/2009) that imposes the employment of cooked or concentrated musts obtained from grapes. Efficient and robust methods for assessing the authenticity of grape musts are required to face the frequently occurring ABM adulteration. Seventy-two grape musts (concentrated, cooked, and rectified) produced in Europe were analyzed via Isotope-Ratio Mass Spectrometry to determine the delta 13C values of glucose and fructose and Nuclear Magnetic Resonance (NMR) spectroscopy. The results showed that 25 out of 35 concentrated musts had delta 13C values higher than-24 parts per thousand, introducing the doubt that these samples were not obtained from grapes. 1H NMR analysis supported this evidence highlighting the absence of organic acids, amino acids, and polyphenols naturally present in grape musts. Additionally, the NMR results indicated that all concentrated musts might be non-authentic due to the lack of such metabolites, introducing doubts on the reliability of the IRMS analysis. The preliminary results obtained lay the foundation for developing a more solid approach based on IRMS and NMR methods for the authentication of concentrated and/or cooked grape must after building an extended library.