Authentication and Geographical Characterisation of Italian Grape Musts through Glucose and Fructose Carbon Isotopic Ratios Determined by LC-IRMS

Abstract

The authenticity of grape musts is normally checked through a time-consuming stable isotopic analysis of carbon (δ13C) after fermentation and distillation by following the official OIV MA AS-312-06 method. In this study, the alternative use of a technique based on δ13C isotopic analysis of the major sugars of the grape must by liquid chromatography coupled with isotope ratio mass spectrometry (LC-IRMS) is provided. It allows not only the detection of the fraudulent addition to grape must of exogenous glucose and fructose deriving from C4 plants but also the characterisation of it based on its geographical origin. In order to discriminate between musts from different areas of Italy, a preliminary dataset was considered; the δ13C isotopic ratios of glucose and fructose of around 100 authentic samples were analysed. The two analysed parameters, ranging from −29.8‰ to −21.9‰, are well correlated (R2 = 0.7802) and the northern regions showed significantly more negative δ13C values for both sugars than the rest of the dataset.