Effects of Leaf Removal on Free and Glycoconjugate Aromas of Skins and Pulps of Two Italian Red Grapevine Varieties

Leaf removal is a cultural practice mainly aimed at improving cluster zone microclimates and impacting primary and secondary metabolites, such as volatiles. This research aimed to assess the impact of defoliation on free and glycosylated aromas of a neutral ('Nebbiolo') and a semi-aromatic ('Aleatico') red variety. Defoliation was performed at fruit set (BBCH 71) and, for 'Nebbiolo', also at berries touch (BBCH 81) phenological stages. Skins and pulps were separately analyzed by Solid Phase Extraction-Gas Chromatography/Mass Spectrometry. Results showed that the response to defoliation was variety-dependent. For 'Nebbiolo', especially when performed at the berries' touch stage, defoliation had a significant effect on the accumulation of free volatiles and glycosidic precursors. Differently, free and bound 'Aleatico' volatiles were less impacted by defoliation. Interestingly, in both grapevine varieties, defoliation significantly enhanced the accumulation of aroma precursors in grapes' skins, which is of particular relevance for red wine production and their aging potential. Moreover, results could be helpful for the management of grape quality, as defoliation is currently considered as a strategy to address climate change issues.

Effects of oenological tannins on aroma release and perception of oxidized and non-oxidized red wine: A dynamic real-time in-vivo study coupling sensory evaluation and analytical chemistry

Addition of oenological tannins claims to have a positive impact on wine stability, protection from oxidation and likely sensory persistence. However, their role on red wine aroma during oxidation is controversial. The present study aims at investigating the effect of addition of oenological tannins on wine flavour (mainly aroma) before and after air exposure. Temporal Dominance of Sensations, a dynamic sensory evaluation, was coupled with a dynamic chemical measurement (nosespace analysis) using a Proton-Transfer-Reaction Mass-Spectrometer connected to the nasal cavity of 17 assessors. Results showed that the oxidation of a non-oaked Pinot Noir red wine decreases the fruity aroma dominance and increases the maderised and prune one. A contextual decrease of the fruity ethyl decanoate and increase of oxidative Strecker aldehydes are observed. Ellagitannins but not proanthocyanidins preserved perception of fruitiness and prevented increase of maderised notes. Moreover, ellagitannins increase the aroma persistence mainly in the non-oxidized wine.

Preliminary results on tartaric stabilization of red wine by adding different carboxymethylcelluloses

Despite being natural phenomena of physical-chemical stabilization of young wines, tartrate precipitations in bottled wines are often understood as a quality fault. Carboxymethylcellulose (CMC) is an inhibitor of tartaric salts crystallization, authorized as oenological additive, which application is currently limited to white and sparkling wines by OIV. The aim of this exploratory research was to study the effect of different CMC on a (tartaric) unstable red wine, in terms of tartrate stability, colouring matter stability, turbidity, comprehensive phenolic composition, and chromatic characteristics. All the CMC tested were able to inhibit potassium bitartrate crystallization in the red wine, promoting its tartaric stability. Slight increase in the colour intensity, coloured anthocyanins concentration, and turbidity of the wine were observed. No colouring matter precipitation was verified. The study seems to indicate that the CMC can be an efficient alternative to other tartaric stabilization treatments, also in red wines, opening new prospective and scenarios concerning the use of CMC in this type of wines.