Wine evaluation | Dealing with wine flaws

By Charl Theron

Fortunately wine is a natural product and not just a commodity which is manufactured. That is also the reason why wine is made in a cellar and not in a factory. Being natural is however not only an advantage, because everything natural is exposed to the environment, which can obviously lead to improvement in quality but also possible deterioration in the case of diseases.

Assigning the cause of off-flavours in wine is like diagnosing diseases in patients. The winemaker needs to look at the symptoms of the wine when deciding what the problem is. After the diagnosis is made the corrective actions can be implemented. This may be remedial in nature or preventive for  future making of similar wines. Like human beings, the diagnosis may also find that the symptoms are actually side-effects and not the real problem. If wine is kept in barrel for a long time there will, for example, be an increase of the volatile acidity (va) of the wine. An increase of va as such is however usually seen as microbiological instability. By looking at the va only, without considering the barrel maturation, a wrong conclusion may result.

Wine flaws occurring most frequently are oxidation, vinegar character (vc), cloudiness or turbidity and the so-called ‘Brett’ character.

Oxidation
Oxidation will lead to white wines with a brownish colour and red wines with a brick-red colour. Flavour descriptors of such wines will be ‘sherry-like’ and ‘bruised apple’ for white wines and ‘porty’ or ‘jammy’ for red wines.

Vinegar character
Any indication of vinegar character in wine is always negative and is the result of microbiological action or long barrel maturation.

Cloudiness or turbidity
Cloudiness or turbidity in wines can be the result of a secondary fermentation of the residual sugars in the wine or the conversion of other wine constituents by yeasts or bacteria. Chemical instabillity may also cause the formation of cloudiness or crystals.

Brett character
The Brett character is associated with leather, sweaty horse, barnyard, band-aid or smoky flavours and is the result of microbiological contamination of an unwanted yeast called Brettanomyces.

Fortunately the wine flaws can be prevented by applying sound cellar practices like the following:

• Containers should be kept full to protect it against oxygen.
• The correct use of sulphur dioxide, a general preservative and antioxidant, used during winemaking.
• General sanitation in the cellar.
• Protection from light and extreme or fluctuating temperatures.
• The use of sound fruit with no diseases or damaged clusters.
• The use of acknowledged yeast and bacteria for the microbiological processes of winemaking.

Wine hint of the month: 2008 Boplaas – ‘The Chocolate Port’. Deep red, fruity with  pleasant dry tannins on the palate.

Charl Theron is the Course Convenor for the Stellenbosch University Wine Evaluation Course. Charl has been involved in the wine industry for 40 years. He was initially involved at different production and management positions at KWV for 30 years, before joining the University of Stellenbosch as extraordinary lecturer in enology.

Click here if you would like to learn more about the Stellenbosch University Wine Evaluation Course.

Back to SmartyPants Newsletter - April 2010 Edition