Compuestos azufrados volátiles en vinos - Fundación para la ...

colour composition. Analytical parameters related tocolour intensity and hue were indeed found to varywith DAP supplementation (Ugliano et al. 2007). Thefactors responsible for this eff ect are currently beinginvestigated at the AWRI. The eff ect might be ascribableto various aspects of yeast metabolism thatare known to modulate wine colour and phenolicscomposition. Factors include variations in the rate ofethanol production, absorption of anthocyanins onyeast cell walls (Morata et al. 2003) or reactions withyeast-derived metabolites such as pyruvic acid andacetaldehyde to form pigmented polymers (Romeroand Bakker 1999).CONCLUSIONThis work shows that the concentration of yeast assimilablenitrogen is not only important for ensuringthat adequate yeast growth and fermentation kineticsare achieved, but also can aff ect the production ofthe major metabolites arising from sugar fermentation.Whereas ethanol concentration is little aff ected,that of glycerol and various carboxylic acids can bemarkedly modulated. These changes are likely to affect wine fl avour. Most importantly, however, is the finding that YAN can strongly infl uence production ofsome of the volatile metabolites, especially the acetateand ethyl esters, which are known to be positiveto wine aroma when in balance. The impact of higheralcohols, which can be negative when present in highconcentration, can also be modulated by YAN. Thesevarious yeast metabolites were also found to vary inConcentration µg/L10,0009000800070006000500040003000200010000100mg/L YAN 250mg/L YAN 400mg/L YANFatty acids ethyl estersAcetatesEthyl acetateHigher alcohols/100Figure 7. Volatile compounds of wines obtainedfrom low YAN (100mg/L YAN) Shiraz grapessupplemented with two increasing concentrationsof DAP, to a fi nal YAN of 250mg/L and 400mg/Lrespectively. Fermentations were carried outat 22ºC using S. cerevisiae AWRI 796, with capplunging three times per day.Seminario TécnicoCompuestos azufrados volátiles en vinosred wine fermentations, suggesting that, as in whitewines, must YAN can aff ect the development of winefl avour. Our preliminary data suggest that wine colourand phenolics composition can also be infl uencedby YAN.Overall, these results suggest that, at least for Chardonnay,the fl avour and style of wine is dramaticallymodulated by the initial YAN concentration of the grapejuice. Low YAN level juices favour the production ofmore complex wines with less fruity aromas, whereasmoderate YAN levels produce cleaner and fruitier wines.However, high YAN levels can lead to excessivelyestery wines. Similar eff ects can be expected in othervarieties, excepting for those varieties that depend onthiols, for which no information is presently available.Clearly, more wine sensory studies need to be undertakento better understand the eff ects of must YANand amino acid profi le on wine fl avour.A red wine trial is currently in progress to understandbetter the impacts of managing nitrogen in the vineyardcompared with that in the winery on wine flavour and quality. This research can be expected toprovide grapegrowers and winemakers with betterinformation for optimising wine style and quality accordingto consumer preferences and other desiredoutcomes.ACKNOWLEDGEMENTSWe thank our many colleagues for supporting thisproject, especially Tracey Siebert and Dimitra Caponefor help with analysis of fermentation volatiles; MariolaKwiatkowski and Meagan Mercurio for analysisof phenolic compounds; Kate Lattey, Belinda Bramleyand Dr Leigh Francis for carrying out the sensoryanalyses; Industry Development and Supportand Analytical Service team members for help withchemical analyses; and Dr Paul Chambers, Dr CristianVarela and Biosciences team members for manyhelpful discussions. Professor Francisco Carrau, ofUruguay, and visiting scientists Drs Diego Torrea andMar Vilanova, from Spain, have made important contributionsto this project. We are especially grateful toMike Farmilo, of Boar’s Rock winery, for supplying alarge number of juice samples and donating must forthe Shiraz fermentation trials, and Russell Johnstoneand Inca Pearce, of Orlando Wines, and Louisa Roseand Simon Dillon of The Yalumba Wine Company, forsupplying white wine juices. Current work on nitrogenmanagement also involves collaboration with DrSally-Jean Bell and Marcel Essling. Rae Blair is thankedfor her editorial assistance. This project is supportedby Australia’s grapegrowers and winemakers throughtheir investment agency, the Grape and Wine Researchand Development Corporation, with matchingfunds from the Australian Government. The AWRI is amember of the Wine Innovation Cluster.Textos asociados69