HPLC-DAD-MS/MS characterization of phenolic compounds in white wine stored without added sulfite

The oxidation of dihydroxybenzene and hydroxycinnamate compounds generates unstable quinones which undergo further reactions to combine nucleophilic compounds. These reactions are limited when sulfur dioxide (SO2) is used as wine preservative, as SO2 plays an important role in reducing quinones back to their phenol form. In no sulfite-added wine, oxidation chemistry undoubtedly results changed. Therefore, in this work, the phenolic profile of a white wine without adding sulfites, after twelve-month storage, was investigated by HPLC-DAD-MS/MS and compared to a control stored with sulfur dioxide. A total of twenty-six phenolics were detected including hydroxycinnamate derivatives and minor compounds resulting from oxidation processes, i.e. oxidized caffeic acid dimers, whose structures were tentatively proposed on the basis of their UV, MS, and MS/MS typical fragmentation. The experimental evidence of these latter is described for the first time in wine stored without added sulfites, and it may contribute to get new insight in the field of wine oxidation processes.