Effect of oxygen exposure during fermentation on volatile sulfur compounds in Shiraz wine and a comparison of strategies for remediation of reductive character.

Background and Aims Oxygen ( O₂) plays a fundamental role in the establishment of wine style and aroma. The effect of O₂ treatment during fermentation on the formation of volatile sulfur compounds ( VSCs) and the subsequent impact on the sensory profile of wine was investigated. Traditional VSC remediation strategies were also evaluated. Methods and Results Shiraz wines were treated with O₂ at several levels during fermentation by sparging rotary fermenters with three types of gas mixtures (40% O₂, 21% O₂ and N₂). The controls were not sparged with any gas and were subsequently subjected to three remedial treatments (aerative racking, early- and late- Cu²⁺ addition). Wines were analysed for VSCs, fermentation products, concentration of residual metals, as well as their sensory profile. Non-oxygenated ferments and wines contained a higher concentration of VSCs and a lower concentration of fermentation products and differences in the concentration of metals. Volatile sulfur compounds responsive to O₂ treatment were identified and a relationship between O₂ dose and concentration on VSC formation was demonstrated. The 'early- Cu²⁺ addition' remediation strategy proved the most effective in reducing the impact of 'reductive' aromas in non-oxygenated wines. Conclusions The risk of producing a wine with high VSC concentration that negatively impacts wine aroma as well as with a low concentration of fermentation products associated with positive red fruit aromas was decreased by treating wines with O₂ during fermentation. Significance of the Study This work specifically examines important aspects of O₂ treatment during fermentation in relation to 'reductive' aroma characters and the overall impact on the wine's sensory attributes. [ABSTRACT FROM AUTHOR]