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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. Source

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. Source

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. Source

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. Source

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. Source

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