Comparison of remediation strategies for decreasing ‘reductive’ characters in Shiraz wines

• Published in: Australian journal of grape and wine research Vol. 27; no. 1; pp. 52 - 65
• Main Authors: Bekker, M.Z., Espinase Nandorfy, D., Kulcsar, A.C., Faucon, A., Bindon, K., Smith, P.A.
• Format: Journal Article
• Language: English
• Published: Melbourne John Wiley & Sons Australia, Ltd 01-01-2021; Wiley Subscription Services, Inc
• Subjects: Aeration; Aroma; Bottling; Copper; Copper compounds; copper fining; Fermentation; hydrogen sulfide; metals; oxygen treatment; Oxygenation; Reduction; reductive aromas; Remediation; sensory descriptive analysis; Sensory evaluation; Sulfur; Sulfur compounds; volatile sulfur compounds; Wine; winemaking; Wines
• ISSN: 1322-7130; 1755-0238
• DOI: 10.1111/ajgw.12459

Background and Aims
Winemakers utilise various remediation strategies for decreasing ‘reductive’ characters in wine. Remediation strategies, such as the addition of diammonium phosphate (DAP) during fermentation, copper fining, the addition of fresh lees or lees products to wine, and aeration of the must during and after fermentation, are commonly employed in an effort to prevent the formation or to remove undesirable volatile sulfur compounds. In this study, the relative effectiveness of five strategies for remediation of ‘reductive’ aroma was compared in a Shiraz wine.
Methods and Results
At the onset of the development of ‘reductive’ aromas during Shiraz fermentation, each ferment was treated with a unique remediation strategy: DAP addition; macro‐oxygenation; copper fining; a combination of macro‐oxygenation and copper fining; or the addition of fresh lees from a donor wine. While a relatively small difference in volatile sulfur compounds was found between treatments, copper fining, lees and DAP addition produced wines with elevated ‘reductive’ characters at certain time‐points post‐bottling; while macro‐oxygenation or macro‐oxygenation with copper produced wines with a low sensory score for ‘reduction’‐related attributes.
Conclusions
Macro‐oxygenation during fermentation was the most effective remediation strategy. Lees addition, and to a lesser extent, copper fining and DAP addition, diminished fruit attributes and produced wines with noticeable ‘reductive’ characters.
Significance of the Study
Macro‐oxygenation during fermentation produced wines with the lowest ‘reduction’‐related attributes while enhancing ‘fruity’ attributes. This work also highlighted the compositional effects of each type of remediation treatment.