Astringency characterization of tannat red wine

Abstract

Tannat is a red variety of Vitis vinifera that has become the emblematic red wine variety of Uruguay. Tannat wine is characterized by its high total phenolic content, which provides a good potential for aging and differential sensory characteristics. The aim of the present thesis was to characterize the astringency of Uruguayan Tannat wines from both a physicochemical and sensory perspective. Astringency is a complex and timedependent attribute, which exhibits buildup and carry over effects upon repeated ingestions, and is related to several subtle sensations that can be perceived simultaneously. This poses several challenges for the accurate sensory characterization of Tannat wine astringency, which have been addressed during the development of the thesis. First, qualitative studies with consumers were carried out to understand their conceptualization of astringency and the vocabulary they use for describing this complex attribute. Basic research about the applicability of different palate cleansers for wine astringency evaluation was also conducted. The astringency of 40 commercial wines was characterized using static and dynamic sensory methods: Time-Intensity (TI), checkall- that-apply (CATA) questions and Temporal Dominance of Sensations (TDS). The TI evaluations performed by a panel of trained assessors showed that commercial Tannat wines mainly differed in intensity-related parameters rather than in astringency development over time, although the variability was moderate. CATA questions involving 16 astringency sub-qualities proved to be a valuable tool to describe and differentiate a large sample set of Tannat wine samples based on their astringency characteristics. Different styles of Tannat wine were identified, which were described using a wide range of sub-qualities, from silky and velvety to harsh and aggressive. The phenolic profile of the 40 commercial Tannat wines was also characterized using reversed phase high performance liquid chromatography coupled with a mass spectrometer (HPLC-MS) and its relationship with sensory astringency was explored using boosted regression trees. The total content of condensed tannins as well and some specific phenolic compounds were identified as the main predictors of sensory astringency. Finally, the comparison of astringency evaluation of trained assessors and experts showed that their intensity assessments were partly related, but their description of astringency sub-qualities differed. Insights on the astringency sub-qualities related to expert s perception of astringency quality were also revealed. Results from the thesis provide both methodological insights about astringency evaluation, as well as applied information about the astringency of Tannat wine, which could be highly valuable for the Uruguayan