Wine faults

Question 1

Wine faults (9)

Answer 1

Most wines these days is technically fault free because of the care taken at every stage at the production process. Sorting out damaged fruit, exclusion of oxygen on key points, temp control, hygiene in wineries, stabilisation etc

Nonetheless, some wine faults continue to be seen:

• Cloudiness and hazes
• Tartrates
• Re-fermentation in the bottle
• Cork taint
• Oxidation
• Volatile acidity
• Reduction
• Light strike
• Brettanomyces

Question 2

Cloudiness and hazes

Answer 2

Wines can be unclear for several reasons;

Growth of yeast or Bactria in wine coupled with failure to filter adequately which can be avoided by better hygiene in the winery, pre-bottling chemical analysis and filtering wine to remove yeast or bacteria before bottling

Cloudiness may also come from poor filtering, pumping wine at too high pressure through ta depth filter so that unwanted molecules go through the filter

Cloudiness can be due to a protein haze where fining is not effective. If the wrong type of fining agent is used or the wine is over-fined this results in unstable proteins remaining in the wine, causing it to go hazy

The remedy is to fine correctly and conduct analysis after fining

Question 3

Tartrates

Answer 3

Colourless or white crystals at the bottom of the bottle

Consumers may see this as a fault, but knowledgeable drinkers it’s a natural precess triggered by low temperatures and is completely harmless to health and wine quality

Most inexpensive and mid-priced wines are stabilized before realize from the winery, but occasionally this is not completely successful

Question 4

Re-fermentation in the bottle

Answer 4

Consumers may see visible bubbles or spritz as a fault. However, some wine style purposely include a low level of spritz (Muscadet sur lie or Vinho Verde) and some inexpensive white wines will have a small amount of CO2 added before bottling, to preserve and enhance freshness

If the spritz or bubbles are accompanied by cloudiness, it would be unwanted re-fermentation in the bottle

Question 5

Cork taint

Answer 5

Moldy, wet cardboard smell, which also reduces the fruit character and shortens de finish of the wine

Question 6

Oxidation

Answer 6

The result of excessive exposure to oxygen either during the winemaking process or once in the bottle or container

The later can be due to faulty bottling, poor quality corks or plastic closures, or for simply keeping the wine long if if it’s not suitable to age

The wine becomes brown in flour with a loss of primary fruit and then a vinegar smell

Question 7

Volatile acidity

Answer 7

Excessive amounts give a pungent smell of nail polish remover and vinegar

Due to the activity of acetic acid bacteria, inadequate levels of so2 and excess exposure to oxygen

Can be reduced by sorting fruit to exclude damaged grapes, good hygiene in the winery, keeping vessels topped up, careful racking (to avoid excessive exposure to oxygen) and maintaining so2 levels adequate

Question 8

Reduction

Answer 8

Associated with sulfur-like aromas, ranging from onion to rotten eggs

Caused by high levels of volatile, reductive sulfur compounds. Regarding to the concentration of these compounds some aroma (struck match and smoke) can give complexity in wine

However, at higher concentrations they produce unwanted aromas of rotten egg that will always be regarded as a fault

The sulfur compounds are produced by yeast under stress (low nitrogen levels)

Reduction can occur due to the near complete exclusion of oxygen during aging in closed vessels, especially when lees aging (forming a layer on top). Reduction can be avoided by ensuring yeast has sufficient nutrients and oxygen, and that the must is at an adequate temperature

Question 9

Light strike

Answer 9

Caused by UV radiation and certain wavelengths of visible light reaction wit certain compounds in the wine to form volatile sulfur compounds, giving smells like dirty drains

Wines left in direct sunlight are most at risk, but wines near fluorescent lightning (displays in retailers) are also at risk as well as wines packed in clear glass, green or brown glass will offer better protection

Question 10

Brettanomyces

Answer 10

Brett proces a range of off-aromas ranging from animal smell, spicy or farmyard smells

Some tasters believe it adds complexity to red wines if levels are low

At higher levels its clearly a fault in which off flavours dominate fruity flavours

Once it occurs in the winery its hard to destroy, especially as wood can host the organism and be very difficult to clean effectively

The keys to avoid Brett are:

• Excellent hygiene
• Maintaining effective so2 levels
• Keeping pH levels low and keeping the period between alcoholic fermentation and malolactic conversion as short as possible so that so2 can be added as soon as possible