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Wine spoilage discussed at Sasev workshop
by Edo Heyns
Well-known winemaker, Francois Naudé started proceedings by giving a winemaker’s perspective on TCA problem wines, which are often referred to as ‘corked wines’. Even though corks can be major culprits associated with TCA and similar unwanted components (scientifically referred to as organohalogens), other sources such as packaging materials, treated wood and even cellar water could be part of the issue. According to Naudé, consumers have become more aware and educated concerning the problem and winemakers should therefore pay more attention to it. He also commented on the term ‘corked’, saying that cork manufacturers immediately get the blame for what is often poor cellar hygiene practice and urged winemakers to move away from that term and rather refer to “tainted” wines. Dr Viresh Ramburan (US) represented Quantum Laboratories, discussed trends observed in the South African industry, proving that through testing of corks and other materials for TCA, winemakers are increasingly taking note of the problem and that regular testing could prevent potentially harmful situations. As a partnership between Stellenbosch University and Thales Wine Cellar Services, Quantum focuses on the analysis of corks, wines and cellar materials for TCA and related compounds and in so doing provides a service to the wine industry. Viresh stated that sensory evaluation of wine is inadequate for quality control. Due to their importance, odour compounds such as TCA require accurate measurement in a complex medium such as wine. For this reason, analytical methods incorporate solid phase micro extraction (SPME), solid matrix extraction (SME) and liquid matrix extraction (LME), which are all done through expensive GC-electron capture detection equipment (GC-ECD). In reaction, attending winemakers questioned the pricing of analyses, suggesting research into alternative and less expensive methods be sought. The detection level of TCA in wine varies considerably between wine styles and tasters. In this light, De Trafford winemaker, David Trafford, even suggested using trained dogs to detect faulty wines – something that was received well and is not that far fetched considering what K9 noses are already being applied for.
Speaking about chemical taints in the cellar, Thales’ Adriaan Oelofse made it clear that prevention is better than cure. He referred to chlorine and bromine contamination (TCA, TBA etc.) in cellars as the most likely, potentially problematic compounds and discussed their origin and synthesis as well as problematic sources. Backing his prevention theory, Oelofse also mentioned some less obvious causes of contamination such as a lack of aeration in cellars and recommended cellar hygiene audits to assure that such problems, that would usually be dismissed, are identified. He also warned winemakers about problems around incorrect sampling and aroma screenings as well as other direct contamination possibilities via oenological agents that are usually seen as ‘safe’, such as filter sheets, yeasts, fining agents and water. Sasev chairperson, Prof Maret du Toit – who is also very knowledgeable on the subject of wine spoilage – said that the need and role of such awareness sessions is clearly showing through the participation and questions that arose during the workshop.
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