ALCOHOLIC FERMENTATION AND COLOR OF ROSÉ WINES: INVESTIGATIONS ON THE MECHANISMS RESPONSIBLE FOR SUCH DIVERSITY

Wine complexity is considered a multidimensional yet equivocal sensory percept. This project uncovered sensory attributes Australian Chardonnay wine consumers associate with Chardonnay wine complexity
and correlations between expert and consumer perceived wine complexity and preference. A
wine consumer test examined 6 Australian Chardonnay wines of three complexity levels designated low (LC1&2), medium (MC1&2), and high (HC1&2) by an expert panel (n = 8) using a benchtop sensory task. Consumers (n = 81) rated their perceived liking using a 9-point hedonic scale; wine complexity with a 5-point scale anchored “low”, “low-medium”, “medium”, “medium-high”, and “high” and lastly, profiled the wines using Rate-All-That-Apply (RATA). Psychographic segmentation with the Fine Wine Instrument
(FWI) generated three segments; Wine Enthusiasts (WE n=29), Aspirants (ASP n=40) and No- Frills (NF n=12).

According to winemakers, wine experts and sommeliers, aromas of wet stone, mineral, struck match and flint in white wines styles, such as those produced from Vitis vinifera L. cv. Chardonnay, are considered to be hallmarks of positive reduction.1,2 In recent years, the production of Chardonnay styles defined by aroma characteristics related to positive reduction has become more desirable among wine experts and consumers. The chemical basis of positive reduction is thought to originate from the concentration of specific volatile sulfur compounds (VSCs), including methanethiol (MeSH) imparting mineral and chalk notes,3 and benzenemethanethiol (BMT) responsible for struck match and flint.1,4

The synthetic herbicide glyphosate has been used extensively in viticulture over many decades to combat weeds. Despite this, the possible influence of residual glyphosate on both the alcoholic fermentation of grape juice and the subsequent metabolite profile of wines has not been investigated. In this study, Pinot noir juice supplemented with different concentrations of glyphosate (0 µg L-1, 10 µg L-1 and 1000 µg L-1) was fermented with commercial Saccharomyces cerevisiae yeast strains. Using a combination of analytical methods, 80 metabolites were quantified in the resulting wines.

In recent years characterized by hot dry summers, the implementation of innovative irrigation tools in the vineyard represents a crucial challenge to ensure optimal production and to avoid excess of water consumption. It is known that the grapevine reacts to multiple stresses – i.e., high temperatures and wa- ter shortage – through adaptive mechanisms that are detrimental to the yield. Furthermore, this condi- tion is usually aggravated by high solar radiation, which could negatively affect the phenolic composi- tion of the grapes. Therefore, a cooling system has been developed aiming to reduce bunches’ sunburn damage.

Wine flavanols are extracted from grape skin and seeds along red winemaking. Potentially, eight flavan-3-ol subunits may be present as monomers or as tannins constituents, being these catechin, epicathechin, gallocatechin, epigallocatechin end the gallates of the mentioned units. In this work the flavanol profiles of grape skins and seeds before (grapes) and after (pomace) red winemaking were studied together with the one in the corresponding wines. The trials were made over two vintages in Vitis vinifera cv. Tannat, Syrah and Marselan from Uruguay.