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Ugliano M.,Nomacorc SA | Dieval J.-B.,Nomacorc SA | Siebert T.E.,Australian Wine Research Institute | Kwiatkowski M.,Australian Wine Research Institute | And 5 more authors.
Journal of Agricultural and Food Chemistry | Year: 2012

The evolution of different volatile sulfur compounds (VSCs) during bottle maturation of two Shiraz wines submitted to controlled oxygen exposure prior to bottling (through micro-oxygenation, MOX) and postbottling (through the closure) was investigated. H2S, methyl mercaptan (MeSH), and dimethyl sulfide (DMS) were found to increase during aging. Lower postbottling oxygen exposure, as obtained by different degrees of oxygen ingress through the closure, resulted in increased H2S and methyl mercaptan. In one wine MOX increased the concentration of H2S and methyl mercaptan during maturation. Dimethyl disulfide and DMS were not affected by any form of oxygen exposure. Overall, postbottling oxygen had a stronger influence than MOX on the evolution of VSCs. Data suggest that dimethyl disulfide was not a precursor to methyl mercaptan during bottle maturation. For the two wines studied, a consumption of oxygen of 5 mg/L over 12 months was the most effective oxygen exposure regimen to decrease accumulation of MeSH and H2S during bottle aging. © 2012 American Chemical Society.


Chalmers Y.M.,Australian Department of Primary Industries and Fisheries | Chalmers Y.M.,University of Adelaide | Downey M.O.,Australian Department of Primary Industries and Fisheries | Krstic M.P.,Australian Department of Primary Industries and Fisheries | And 4 more authors.
Australian Journal of Grape and Wine Research | Year: 2010

Background and Aims: This study aimed to explore the influence of sustained deficit irrigation (SDI) on the grape and wine colour parameters of two premium red wine grape varieties grown in the Sunraysia region of South Eastern Australia. Methods and Results: The SDI experiments were conducted during three vintages from 2003 to 2004, 2004 to 2005 and 2005 to 2006 on the Vitis vinfera cultivars Cabernet Sauvignon and Shiraz grafted to 140 Ruggeri (V. berlandieri × V. rupestris) rootstock. The grapevines were drip irrigated providing 100% of estimated ETc (control) and three graded sustained water deficits (Cabernet Sauvignon 70, 52 and 43% of the control; Shiraz 65, 45 and 34% of the control). Microscale wine fermentations were conducted on grapes from the 2006 harvest to assess wine colour density, wine hue, red pigments, anthocyanins, phenolics and copigmentation products in the wine. Wine anthocyanin and phenolic concentrations for both varieties showed significant increases with increasing intensity of SDI. Conclusion: Increases in wine colour with SDI may result from changes in flavonoid biosynthesis as a result of grapevine responses to water deficit. Alternatively, increases in red wine colour could be caused by changes in chemical properties of the anthocyanins to copigmented or polymeric forms during the winemaking or ageing process. Significance of the Study: The Australian wine industry is currently affected by drought and reduced water allocations resulting in production of wine from grapes exposed to water deficit. Findings from this study provide knowledge to the wine industry as to how sustained deficit irrigation may modify wine colour. © 2010 Australian Society of Viticulture and Oenology Inc.


Gawel R.,The Australian Wine Research Institute | Schulkin A.,The Australian Wine Research Institute | Smith P.A.,The Australian Wine Research Institute | Waters E.J.,The Australian Wine Research Institute | Waters E.J.,Grape and Wine Research and Development Corporation
Australian Journal of Grape and Wine Research | Year: 2014

Background and Aims: Caftaric acid and Grape Reaction Product (GRP) are abundant phenolic substances in white wine. Reports of their sensory effects are confined to individual threshold assessments and anecdotal evaluation of their contribution to mouthfeel. This study profiles the taste and texture of mixtures of caftaric acid and GRP when presented at concentrations typical of white wine. Methods and Results: Mixtures of caftaric acid and GRP, isolated from white wine by countercurrent chromatography, were added to a model wine using a 3×3 full factorial design, and their taste and texture were profiled by trained assessors. Grape Reaction Product suppressed astringency and added to oily mouthfeel, while caftaric acid suppressed the burning sensation from GRP. Neither GRP nor caftaric acid elicited significant bitterness. Conclusions: Caftaric acid and GRP suppressed textural characters elicited by each other, and also by acidity, without contributing significantly to bitterness. Significance of Study: The ability of caftaric acid and GRP to reduce burning and drying sensations without adding to bitterness suggests that they can potentially contribute positively to white wine texture. Oxidative juice handling may contribute to oily mouthfeel that typifies some wine styles. © 2013 Australian Society of Viticulture and Oenology Inc.


Marangon M.,The Australian Wine Research Institute | Lucchetta M.,University of Padua | Duan D.,Fosters Group | Stockdale V.J.,Treasury Wine Estates | And 5 more authors.
Australian Journal of Grape and Wine Research | Year: 2012

Backgrounds and Aims: Bentonite is commonly added to white wines to remove the grape proteins responsible for haze formation. Despite being effective, this technique has drawbacks; thus, new solutions are desirable. The ability of carrageenan and pectin to remove heat-unstable grape proteins, and the impact that such addition has on the physicochemical and sensorial profile of a wine were assessed. Methods and Results: Carrageenan and pectin were added separately or in combination to a Chardonnay juice prior to fermentation. Both adsorbents removed proteins (up to 75%), thus increasing wine protein stability. Carrageenan was more effective than pectin at increasing wine protein stability. Conclusions: Pectin and carrageenan removed protein and partially stabilized the samples of the wine. Significance of the Study: Pre-fermentation addition of pectin or carrageenan may provide the wine industry with an alternative protein stabilization procedure. © 2012 The Australian Wine Research Institute.


Lucchetta M.,University of Padua | Pocock K.F.,The Australian Wine Research Institute | Waters E.J.,The Australian Wine Research Institute | Waters E.J.,Grape and Wine Research and Development Corporation | Marangon M.,The Australian Wine Research Institute
American Journal of Enology and Viticulture | Year: 2013

Zirconia pellets (25 g/L) enclosed in a metallic cage were added on the second day to fermenting Riesling, Sauvignon blanc, and Semillon juices. After 48 hours, the zirconia-treated juices showed a large decrease in protein content and the resulting wines were heat stable. Compared to control juices, the fermentation rate was significantly increased for two juices and unchanged in the other juice. There were reductions in concentration of some mineral elements and tartaric acid and increases in pH in the resulting wines from the zirconia-treated juices. © 2013 by the American Society for Enology and Viticulture. All rights reserved.


Gazzola D.,University of Padua | Van Sluyter S.C.,Macquarie University | Curioni A.,University of Padua | Waters E.J.,Australian Wine Research Institute | And 2 more authors.
Journal of Agricultural and Food Chemistry | Year: 2012

Residual proteins in finished wines can aggregate to form haze. To obtain insights into the mechanism of protein haze formation, a reconstitution approach was used to study the heat-induced aggregation behavior of purified wine proteins. A chitinase, four thaumatin-like protein (TLP) isoforms, phenolics, and polysaccharides were isolated from a Chardonnay wine. The same wine was stripped of these compounds and used as a base to reconstitute each of the proteins alone or in combination with the isolated phenolics and/or polysaccharides. After a heating and cooling cycle (70 °C for 1 h and 25 °C for 15 h), the size and concentration of the aggregates formed were measured by scanning ion occlusion sensing (SIOS), a technique to detect and quantify nanoparticles. The chitinase was the protein most prone to aggregate and the one that formed the largest particles; phenolics and polysaccharides did not have a significant impact on its aggregation behavior. TLP isoforms varied in susceptibility to haze formation and in interactions with polysaccharides and phenolics. The work establishes SIOS as a useful method for studying wine haze. © 2012 American Chemical Society.


Van Sluyter S.C.,Australian Wine Research Institute | Van Sluyter S.C.,University of Melbourne | Van Sluyter S.C.,Macquarie University | Warnock N.I.,Flinders University | And 6 more authors.
Journal of Agricultural and Food Chemistry | Year: 2013

White wines suffer from heat-induced protein hazes during transport and storage unless the proteins are removed prior to bottling. Bentonite fining is by far the most commonly used method, but it is inefficient and creates several other process challenges. An alternative to bentonite is the enzymatic removal of haze-forming grape pathogenesis-related proteins using added proteases. The major problem with this approach is that grape pathogenesis-related proteins are highly protease resistant unless they are heat denatured in combination with enzymatic treatment. This paper demonstrates that the protease BcAP8, from the grape fungal pathogen Botrytis cinerea, is capable of degrading chitinase, a major class of haze-forming proteins, without heat denaturation. Because BcAP8 effectively removes haze-forming proteins under normal winemaking conditions, it could potentially benefit winemakers by reducing bentonite requirements. © 2013 American Chemical Society.


Gawel R.,Australian Wine Research Institute | Van Sluyter S.C.,Australian Wine Research Institute | Van Sluyter S.C.,Macquarie University | Smith P.A.,Australian Wine Research Institute | And 2 more authors.
American Journal of Enology and Viticulture | Year: 2013

The in-mouth perception of textures of white wine arising from the interactions among white wine phenolics, pH, and alcohol level was evaluated. Phenolics were extracted from white wines and added back to white wines that were adjusted to different pH and ethanol concentrations within wine realistic ranges. Adding phenolics to a white wine at pH 3.3 significantly increased its astringency, but the same addition did not contribute to the higher astringency elicited by the same wine when adjusted to pH 3.0. Higher phenolics generally increased bitterness and viscosity, but the effect depended on the source of the phenolics. Wines with added phenolics were generally perceived to be hotter, and significantly so when the wine was low in alcohol. The combined effect of phenolic content and alcohol concentration on astringency and bitterness was additive, suggesting that alcohol directly contributes to these attributes in white wines. Overall, the tastes and textures produced by white wine phenolics were more pronounced in wines with lower alcohol levels. © 2013 by the American Society for Enology and Viticulture. All rights reserved.


Ugliano M.,Nomacorc SA | Henschke P.A.,Australian Wine Research Institute | Waters E.J.,Grape and Wine Research and Development Corporation
ACS Symposium Series | Year: 2012

The influence of different winemaking variables on the evolution of volatile sulfur compounds during wine storage in the bottle was investigated. Addition of nitrogen to Shiraz grape must in the form of diammonium phosphate resulted in wines developing increased dimethyl sulfide concentration in the bottle when nitrogen was increased from 100 mg/L to 400 mg/L. Presence of glutathione at bottling at a concentration of 20 mg/L resulted in wines with increased H2S after six months in the bottle. Higher exposure to oxygen during bottle storage was detrimental to the preservation of the fruity aroma compound 3-mercaptohexanol, although it also decreased the concentration of the off-odor compounds H2S and methyl mercaptan. © 2012 American Chemical Society.

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