Abstract
The main aims of this work were (i) to summarise the main phenolic compounds that have been used for the evaluation of wine quality and authenticity in the perspective of different oenological and viticultural factors; (ii) to investigate new classes of proanthocyanidins with a macro-cyclic structure; (iii) to apply cyclic proanthocyanidins for the wine quality and authenticity assessment; (iv) to study the effect of vinification in amphorae for the phenolic and volatile profiles of wine; (v) to design a rapid method for the bitterness evaluation in wine. Phenolic compounds are essential antioxidant components of wine determining its chemical and sensory characteristics. Since the phenolic profile depends on a series of factors related to the grape variety, origin, winemaking, and vintage, it could be used as a chemical marker of the wine quality and authenticity. Thus, the research of new markers is always needed for upgrading the knowledge of wine components and providing new tools for detecting possible adulterations. In the introduction of this work, it has been reported how different grape varieties and species, geographical origin, winemaking procedures, wine ageing in various tanks and bottles correlate with phenolic acids, flavonoids, tannins, and stilbenes. Cyclic proanthocyanidins (a novel class of condensed tannins) were identified and confirmed in red Lagrein wine from South Tyrol using HPLC-HRMS/MS with a hydrogen deuterium exchange approach (second and third chapters). These novel phenolic compounds were tested as a set of chemical markers for wine authenticity and quality assessment. Already bottled nineteen white and red South Tyrolean wines were screened and a good discrimination of wines was achieved. The analysis of Pinot Noir wines showed that proanthocyanidins were affected by the specific winemaking conditions and different solubility (in water or water/ethanol mixtures) and extractability (from grapes) of cyclic and non-cyclic proanthocyanidins has been proved (fourth chapter). In fifth chapter, Chardonnay wines produced in three different types of containers (in-amphorae, barrels and barriques) were investigated. The profile of phenolic and volatile compounds allowed to group the samples according to the winemaking material used. In the final chapter, the development of an electronic tongue for the analysis of red wines for the evaluation of total phenolic content and bitterness was presented. The new system was applied for the blended Lagrein and Vernatsch wines and proved to be an an alternative to sensory analysis for the quality control in wineries. This doctoral thesis project has resulted in eight scientific articles that can significantly contribute to the study of natural chemical markers of wine authenticity and quality.