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Managing thiols in South African white wines

by | Oct 28, 2020 | Oenology

Project Number
WW WDT 16-01

Project title
Managing thiols in South African white wines

Project leader
Du Toit, W J

Institution
Stellenbosch University. Department of Viticulture and Oenology

Team members
Du Toit, W J
Coetzee, C

Objectives and rationale

The objectives of this project were to investigate factors affecting the increase of varietal thiols in South African (SA) white wines during fermentation and their preservation during bottle ageing using certain antioxidants. Varietal thiols, such as 3MH and 3MHA, play a crucial role in several cultivars’ guava and passion fruit aromas, such as Sauvignon blanc, Chenin blanc and Colombard.

Methods
Different sulphur-containing compounds were added to white juices under different winemaking conditions. These conditions included using juices from many wineries and sulphur compounds that are permitted to be added to juice under SA wine laws. Antioxidants were also added to white wines just before bottling. Varietal thiols were analysed in these wines after fermentation or bottle ageing.

Key results

Most sulphur-derived compounds added to the juice did not lead to significant increases in 3MH and 3MHA, except for one compound, where significant increases were measured. However, adding certain antioxidants at bottling did not lead to substantial differences in how these thiols evolved during bottle ageing.

Conclusion of discussion

High SO2 and ascorbic acid additions to juice could increase varietal thiol levels, but using one specific compound could lead to more significant increases.

Recommendation to industry / Key take-home message

The compound that was identified in this research should be used responsibly as a commercial product to optimise varietal thiol levels in white wines. Certain winemaking considerations, such as yeast choice, skin contact, and time in contact with the product, are also important.

The Final Report of this project is confidential as it contains Intellectual Property. The commercial product resulting from this research is Nutriferm X, sold by Enartis South Africa. 

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