Oxygen management during the winemaking process

Project Number
WW WDT 06-01

Project title
Oxygen management during the winemaking process

Project leader
Du Toit, W J

Institution
University of Stellenbosch. Department of AgriSciences. Department of Viticulture and Oenology

Team members
Nieuwoudt, H H

Project description
The overall objectives of this project are to ascertain more knowledge regarding the role that oxygen plays in South African wines, both white and red. The first aim of the project is to investigate the effect of very oxidative and reductive winemaking on South African white wines composition and quality. Whole bunch pressing of white cultivars under almost inert atmosphere is becoming more popular in Europe, but has not been investigated according to our knowledge. By using a custom made press, oxygen levels were kept below 0.5 mg/L in the headspace. This led to higher concentrations of phenolics and glutathione. However, the presence of even low concentrations of oxygen resulted in lower concentrations of these compounds. Very reductive conditions on the other hand led to sulphur compounds being formed.

A ratio of ½ anthocyanins to ¼ tannins is considered optimal for red wine maturation and phenolic development in combination with slight oxidation. The second aim of this study is to investigate this unsupported claim. Initial additions of white skins to red juice led to low anthocyanin concentrations and very high T/A ratios. By substituting the skins with pips, more favourable ratios were obtained. The development of these wines over time will thus be monitored.

The third aim is to ascertain whether infrared spectroscopy can be used in combination with the electronic tongue and tasting to monitor the development of oxidation in wine. This will be done in conjunction with researchers from Russia and Denmark.

Poster(s)
Du Toit, W J, Joseph, B, Lisjak, K, Prevue, D and Stander, M. 2006. A novel LCMSMS method to measure glutathione concentrations in grape juice and wine. Poster presented at the 29th National Congress of the South African Society for Enology and Viticulture. 14-17 November, Somerset West, South Africa.

Joseph, B, Oberholster, A, Lisjak, K and Du Toit, W J. 2006. Reductive pressing and juice treatments: Effect on white wine composition. Poster presented 29th National Congress of the South African Society for Enology and Viticulture.14-17 November, Somerset West, South Africa.

Presentation(s)
Du Toit, W J, Joseph, B and Nieuwoudt, H H. 2006. Alternative ways to measure oxidation in wine. Paper presented at the 29th National Congress of the South African Society for Enology and Viticulture.14-17 November, Somerset West, South Africa.

Du Toit, W J and Lisjak, K. 2006. Knowledge transfer to industry as a presentation: Reductive winemaking in South African Sauvignon blanc. Joint South African Society for Enology and Viticulture, Cape Winelab and SA Wine Laboratories Seminar, Stellenbosch, South Africa.

Du Toit, W J. 2006. Reductive winemaking with Sauvignon blanc. Presentation at the Interlab Information Day, Elsenburg Agricultural College, Stellenbosch, South Africa.

Du Toit, W J. 2007. Oxygen in wine. Paper presented at the 58th Meeting of the American Society for Enology and Viticulture. Reno, Nevada, United States.

Du Toit, W J. 2008. Over ageing of white wines. Presentation at the VinPro Information Day. Barrydale, South Africa.

Geldenhuys, L, Oberholster, A and Du Toit, W J. 2008. The effect of macro-oxygenation on wines made of different seed concentrations. Paper presented at the 15th International Enology Symposium. Trier, Germany.

Geldenhuys, L, Oberholster, A and Du Toit, W J. 2008. The effect of macro-oxygenation on wines made of different seed concentrations. Presentation to the Dienstleistungszentrum Landlicher Raum. Neustadt, Germany.

Article
Du Toit, W J. 2006. Nuwe bevindinge rakende askorbiensuur in wyn, WineLand, Mnth July v. 203 (p. 63-64)

Du Toit, W J. 2006. Nuwe bevindings rakende askorbiensuur in wyn, WineLand, Mnth Jul (203) (p. 63-64)

Du Toit, W J, Lisjak, K, Stander, M A, Prevoo, D. 2007. Using LC-MSMS to assess glutathione levels in South African white grape juices and wines made with different levels of oxygen, Journal of Agricultural and Food Chemistry, v. 55 (p. 2765-2769)

Du Toit, W J. 2007. Effect of different oxygen levels on glutathione levels in South African white must and wines, WineLand, Mnth Dec (220) (p. 66-67)

Dissertation
Du Toit, W J. 2006. The effect of oxygen on the composition and microbiology of red wine. PhD. University of Stellenbosch, Stellenbosch.

Lisjak, K. 2007. The role of oxygen in new vinification technologies of white and red wines. PhD. University of Ljubljana,

FinalReport.pdf

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