NMR metabolite profiling of Greek grape marc spirits

This (1)H NMR based study profiles metabolites in Greek grape marc distillates, tsipouro and tsikoudia. Eightysix samples of indigenous and international varieties, stemming from major vine growing regions of Greece were investigated. The monitoring protocol addressed the global metabolic profile of untreated samples and accomplished the unambiguous assignment of 35 metabolites. NMR spectra were acquired by applying the robust, sensitive and rapid WET1D NMR pulse sequence, which succeeded to unveil the presence of minor compounds in a high ethanol matrix. PCA classified the samples according to their provenance, incorporating also information related to the variety, vintage year and production process within each formed regional assembly. Metabolites such as fusel alcohols, polyols, ethyl esters, mono- and di-saccharides were associated with the classification of samples. OPLS-DA ascribed to samples of common regional entity characteristic genotypic metabolites and probed to the potential influence of the vintage effect. Finally, metabolite profiling underlined the influence of the fermentation and distillation procedures.