Project Number
WW WdT 17-03
Project title
Investigating the effect of sparging on white wine
Project leader
du Toit, W J
Institution
Stellenbosch University. Department of Viticulture and Oenology
Completed
2019
Objectives and Rationale
Sparging using inert gasses is often used in the wine industry to lower oxygen levels before bottling, but little research has been done on it. The main aim of this project was to assess the effect of nitrogen sparging on white wine composition, which is relatively unknown. Another objective was to assess factors affecting the efficacy of oxygen removal with sparging.
Methods
A Sauvignon blanc wine treated with different levels of oxygen and exposed to sparging or no sparging under conditions mimicking those in a commercial cellar was bottled and sensorially and chemically evaluated. A Chenin blanc wine had oxygen added and then removed with a nitrogen and nitrogen/carbon dioxide mixed gas at different temperatures at the Department of Viticulture and Oenology (DVO). The effects of using a diffusion stone or not on oxygen removal were also evaluated. The same wine was then also repeatedly sparged with oxygen and nitrogen to assess its effect. Finally, a Sauvignon blanc wine was sparged normally and over-sparged to assess its effect on certain chemical compounds in the wine and its sensorial composition.
Key Results
Sparging in all these trials had a negligible effect on the wine’s chemical and sensorial composition. However, CO2 levels can be reduced, which might affect the mouth feel of the wines. However, during bottle ageing, in the wine where oxygen was added with no subsequent N2 sparging, lower SO2 levels were observed during bottle storage. In the Chenin blanc trials conducted at the DVO, the main factor affecting the efficacy of sparging was the usage of a diffusion stone, while temperature also seems to play a smaller role. Again little changes in the chemical composition (except for CO2 levels) of the wines were observed just after sparging, even when the wines were over-sparged for an hour.
Key Conclusion of Discussion
Sparging can be safely used to drastically reduce oxygen levels just before bottling. This project brought some new findings to the fore on factors affecting the efficacy of this process.
Recommendation to Industry / Key take-home message
Oxygen levels should be lowered with inert gas sparging using a diffusion stone at a temperature that is not too low. Winemakers should be able to do this, when applied correctly, without too much concern for losing aroma compounds from the wine.