A viticultural perspective of Meso-scale atmospheric modelling in the Stellenbosch wine growing area, South Africa

Aims: Wine perceived quality lies on a number of different factors. Among these, sensory features, which are in turn dependent on chemical composition, play a primary role. There is traditionally a great emphasis on producing wines that have specific sensory profiles, particularly aroma, that reflect identity features connected to the place and the variety of origin. In the case of high quality

Accentuated cut edges (ACE) is a novel grape crushing technique used sequentially after a conventional crusher to increase the extraction rate and content of polyphenolics, as shown for Pinot noir wine. This inspired us to apply the technique during Shiraz and Sauvignon blanc winemaking, primarily to assess its impact on the extraction of varietal thiol precursors in grape must/juice and formation of varietal thiols in the resultant wines

Nutrients in municipal treated wastewater (N, P, K, mainly) are a particular advantage in this source over conventional irrigation water sources

Amarone is an Italian red wine produced in the Valpolicella area, in north-eastern Italy. Due to its elaboration with withered grapes, Amarone is a rather unique example of dry red wine. However, there is very limited data so far concerning the volatile composition of commercial Amarone wines, which also undergo a cask aging of 2-4 years before release. The present work aims at characterizing the aroma composition of Amarone and to elucidate the relationships between chemical composition and sensory characters. The analysis of 17 Amarone commercial wines from the same vintage (2015) was carried out by means of Gas Chromatography-Mass Spectrometry (GC-MS) and extracted by Solid Phase Extraction (SPE) and Solid Phase Micro Extraction (SPME). In addition, the sampled wines were subjected to a sensory evaluation in the form of sorting task.RESULTS: 70 volatile compounds were successfully identified and quantified, 30 of which were present in concentrations above their odor thresholds in all the samples. Using the odor activity value (OAV), the compounds that potentially contribute to Amarone perceived aroma are b-damascenone, ethyl and isoamyl acetate, ethyl esters (hexanoate, octanoate, butanoate, 3-methybutanoate), 4-ethyl guaiacol, 3-methylbutanoic acid, dimethyl sulfide (DMS), eugenol, massoia lactone, 1,4-cineol, TDN, cis/trans-whisky lactone. In certain samples, high OAVs were also observed for 4-ethyl phenol and 1,8-cineole.Results from the sorting task sensory analysis showed three clusters formed.

Measurement of carbon isotope discrimination in berry juice sugars at maturity (δ13C) provides an integrated assessment of water use efficiency (WUE) during the period of berry ripening, and when collected over multiple seasons can be used as an indication of drought stress response. Berry juice δ13C measurements were carried out on 48 different varieties planted in a common garden experiment in Bordeaux, France from 2014 through 2021 and were paired with midday and predawn leaf water potential measurements on the same vines in a subset of six varieties. The aim was to discriminate a large panel of varieties based on their stomatal behaviour and potentially identify hydraulic traits characterizing drought tolerance by comparing δ13C and hydroscapes (the visualisation of plant stomatal behaviour as a response to predawn water potential). Cluster analysis found that δ13C values are likely affected by the differing phenology of each variety, resulting in berry ripening of different varieties taking place under different stress conditions within the same year. We accounted for these phenological differences and found that cluster analysis based on specific δ13C metrics created a classification of varieties that corresponds well to our current empirical understanding of their relative drought tolerances. In addition, we analysed the water potential regulation of the subset of six varieties (using the hydroscape approach) and found that it was well correlated with some δ13C metrics. Surprisingly, a variety’s water potential regulation (specifically its minimum critical leaf water potential under water deficit) was strongly correlated to δ13C values under well-watered conditions, suggesting that base WUE may have a stronger impact on drought tolerance than WUE under water deficit. These results give strong insights on the innate WUE of a very large panel of varieties and suggest that studies of drought tolerance should include traits expressed under non-limiting conditions.