Macrowine 2021
IVES 9 IVES Conference Series 9 Analysis of voltammetric fingerprints of different white grape musts reveals genotype-related oxidation patterns

Analysis of voltammetric fingerprints of different white grape musts reveals genotype-related oxidation patterns

Abstract

Must oxidation is a complex process involving multiple enzymatic transformations, including the oxidation of phenolics containing an ortho-diphenol function. The latter process has a primary influence on wine aroma characteristics and stability, due to the central role of ortho-diphenols in the non-enzymatic oxidative reactions taking place during winemaking and in finished wine. Although oxidation of must is traditionally avoided, in recent years its contribution to wine quality has been revisited, and in some cases improvements to wine aroma have been observed with the application of controlled must oxidation. Nowadays there is a great interest in the wine industry towards the identification of specific markers or patterns to characterize and classify the response of grape must to oxidation. In this study, the response of several grape genotypes to application of controlled doses of oxygen was investigated over three consecutive vintages. Healthy grapes were harvested at maturity form a single experimental vineyard and crushed in controlled conditions. The must obtained was submitted to three consecutive oxygen saturations (approx. 8 mg/L of oxygen). Oxygen consumption kinetics were measured using a chemioluminescence multisensor apparatus. Upon consumption of each saturation, samples were submitted to spectrophotometric analyses to assess oxidation-induced changes to relevant parameters such as absorbance at 280 nm, 320 nm and 420 nm. Voltammetric analyses were also carried out using a Nomasense Polyscan potentiostat with screen printed electrodes to assess the evolution of the entire must oxidizable fraction, including ortho-diphenols. Depending on the vintage, between four and eight genotypes were analyzed, with each oxidation experiment carried out in four replicates. Oxygen consumption rates varied considerably among samples and vintages. Genotypes could be divided in slow (0.07-0.17 mg/L/min) and fast (0.35-0.43 mg/L/min) oxygen consuming, and this was not clearly associate with Folin-Ciocalteu index. Minor changes were observed at the end of each oxidation cycle for UV-Vis parameters such as Abs 280 and 320, while Abs 420 generally increased, in particular during the 2015 trial. Electrochemical analysis revealed major changes in the content and profile of oxidizable compounds, which decreased with each oxidation cycle. The patterns of such changes, namely the regions of the voltammogram mostly affected by oxidation, were found to be genotype-dependent, with vintage only having a minor influence. Specific oxidation patterns could be associated with either slow or fast oxygen consuming musts. These data indicate that the response of grape must to oxidation is linked to specific compositional characteristics (phenolic profiles, enzymes etc) which can be more effectively investigated and controlled by electrochemical methods rather than conventional spectrophotometric approaches.

Publication date: May 17, 2024

Issue: Macrowine 2016

Type: Poster

Authors

Maurizio Ugliano*, Jean Baptiste Dieval, Nelly Champeau, Stephane Vidal, Stephanie Begrand

*University of Verona

Contact the author

Tags

IVES Conference Series | Macrowine | Macrowine 2016

Citation

Related articles…

The impact of different yeasts and harvest time on the wine quality of Beihong and Beimei (<I>V. vinifera x V. amurensis</I>)

Beihong and Beimei are two wine cultivars from ‘Muscat Hamberg’ (V. vinifera L.) and wild V. amurensis Rupr., which were released in China in 2008. Here,two enology practices were reported. Firstly, the impact of different yeasts including D254, GRE, K1, D21 and BDX on dry wine quality of Beihong and Beimei was investigated. For Beihong, among wines fermented by all yeasts, residual sugar content was the lowest, total anthocyanin and resveratrol contents were the highest in the wine by D254. However, the wine by D254 had lower titrable acid than those by the other yeasts except BDX.

Ellagitannins and flavano-ellagitannins: concentration ranges in different areas and sensory evaluation

C-Glucosidic ellagitannins, which are the main polyphenolic compounds in oak heartwood, are extracted by wine during aging in oak barrels. Although such maturing of alcoholic beverages in oak barrels is a multi-centennial practice, very little is known on the impact of these ellagitannins on the organoleptic properties of red wine. The objectives of the present investigation were (i) to isolate oak ellagitannins and to hemisynthesize some made-in-wine flavano-ellagitannins, such as acutissimin A; (ii) to analyse their concentration ranges depending on the cultivar area and (iii) to evaluate their sensory impact on the basis of their human threshold concentrations and dose/response relationships in different types of solutions.

Impact of smoke exposure on the chemical composition of grapes

Vineyard exposure to smoke can lead to grapes and wine which exhibit objectionable smoky and ashy aromas and flavours, more commonly known as ‘smoke taint’ [1, 2]. In the last decade, significant bushfires have occurred around the world, including near wine regions in Australia, Canada, South Africa and the USA, as a consequence of the warmer, drier conditions associated with climate change. Considerable research has subsequently been undertaken to determine the chemical, sensory and physiological consequences of grapevine exposure to smoke. The sensory attributes associated with smoke-tainted wine have been linked to the presence of several smoke-derived volatile phenols, such as guaiacols, syringols and cresols [2].

The effect of Nitrogen and Sulphur foliar applications in hot climates

ine nitrogen deficiency can negatively influence the aroma profile and ageing potential of white wines. Canopy management can alter vine microclimate, affect the nitrogen availability and influence the response of leaf senescence. Increasing the nitrogen availability to vines can increase the Yeast Assimilable Nitrogen (YAN) levels in harvested fruit and wine. Studies show that foliar nitrogen and sulphur applications at véraison, on low YAN Sauvignon blanc grapes have an effect on the level of amino acids (Jreij et al. 2009) and on S-containing compounds such as glutathione and thiols (Lacroux et al. 2008), which in turn can influence the formation of major volatiles and the aroma profile of the wine.

Micro-meteorological, compositional and transcriptional study of corvina grape color during ripening

Grape anthocyanin content and composition could affect the quality and the production strategies of red wines. Differences in the pigment composition modify the color properties in terms of hue, extractability and stability. Thus, for the production of a highly qualitative wine such as “Amarone”, variations in the pigment composition are not negligible. The aim of this work was the investigation of the anthocyanin profile changes during ripening in Corvina grapes, the main cultivar for the “Amarone” production. The experiment took place in 2015, in two vineyards located in Valpollicella (Italy).