Faults

Question 1

Faults that can occur in bottled wine?

Answer 1

Cloudiness and haze

Tartrates

Re-Fermentation in bottle

Cork Taint

Oxidation

Volatile Acidity (VA)

Reduction

Light Strike

Brettanomyces

Question 2

What can cause haziness in wine?

Answer 2

Growth of yeast or bacteria in the bottle

Poor filtration of the wine (ex: pumping wine at too high a pressure through a depth filter)

Ineffective fining : unstable proteins remaining in the wine ( wrong type of fining agent has been used)

Over fining

Question 3

Tartrates

Answer 3

Tartrates are colourless or white crystals that can form in the bottle

Tartrates can be prevented with tartrate stabilisation prior to bottling.

Question 4

Cork taint:

Answer 4

An mouldy wet cardboard aroma, caused by microbiological contamination of the cork closure creating trichloroanisol (TCA).

Question 5

Explain oxidation as a fault in wine:

Answer 5

Excessive exposure to oxygen due to faulty bottling, poor quality closures or inappropriate aging. Creates a wine with brown colour, lack of fruit and vinegary smell.

Question 6

What is volatile acidity (VA) in wine and how is it caused?
How is it prevented?

Answer 6

Volatile acidity (VA) is present in all wine. Excessive amounts smell of acetone or vinegar.
Caused by acetic acid bacteria and inadequate levels of SO2.

Avoid damaged grapes Scrupulous hygiene in the winery
Keeping vessels topped up
Careful transfer of wine during racking to avoid oxygen
Maintaining adequate levels of SO2.

Question 7

Define the reduction and possible causes:

Answer 7

Reduction is a catch all term for sulfur-like aromas ranging from onion to rotten eggs, caused by volatile sulfur compounds.
In high concentrations these are regarded as a fault.

Produced by yeast under stress due to low nutrition
Also caused by complete exclusion of oxygen in closed vessels especially during lees aging.

Question 8

How can reduction be avoided?

Answer 8

Ensure yeast is not stressed and has enough nutrients and oxygen.

Ensure adequate temperature.

Lower SO2 levels.

Question 9

Define light strike in wines:

Answer 9

When a wine is exposed to UV radiation from light compounds in the wine can turn into volatile sulphur compounds. Direct sunlight and fluorescent lighting can cause this problem. Wine packaged in clear glass is particularly susceptible.

Question 10

What is Brettanomyces (Brett) and its associated fault?
How it can be avoided?

Answer 10

Brett is a type of wild yeast that is resilient and can inhabit oak vessels
It produces aromas including farmyard, spicy and medicinal smells.
It can reduce fruity flavours in a wine.

• Excellent hygiene.
• Maintaining effective SO2 levels.
• Keeping pH levels low.
• Treat effected wines with DMDC, Velcorin, which inactivates Brett.