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
• 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
• ineffective fining
• over-fining

Question 3

What are tartrates? How can they be prevented?

Answer 3

Tartrates are colorless or white crystals that can form in the bottle, and can be mistaken for fragments of glass.

• can be prevented with tartrate stabilization prior to bottling.

Question 4

What is cork taint?

Answer 4

A moldy 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 color, lack of fruit, and vinegary smell.

Question 6

What is VA in wine, and how is it caused?

Answer 6

VA is present in all wine.

• excessive smell of acetone or vinegar, caused by acetic acid bacteria and inadequate levels of SO2

Question 7

How can VA be prevented?

Answer 7

• 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 8

Define reduction.

Answer 8

• a catch-all term for sulfur-like aromas ranging from onion to rotten eggs
• caused by volatile sulfur compounds, in high concentrations regarded as a fault

Question 9

What causes reduction in wine?

Answer 9

• produced by yeast under stress, due to low nutrition
• can also be caused by complete exclusion of oxygen in closed vessels, especially during lees aging

Question 10

How can reduction be avoided?

Answer 10

• ensure yeast is not stressed, and has enough nutrients and oxygen
• ensure adequate temperature
• lower SO2 levels

Question 11

Define light strike in wines.

Answer 11

• when a wine is exposed to UV radiation from light, compounds in the wine can turn into volatile sulfur compounds
• direct sunlight and fluorescent lighting can cause this problem
• wine packaged in clear glass is particularly susceptible

Question 12

When is Brettanomyces, and its associated fault?

Answer 12

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

Question 13

How can Brett be avoided?

Answer 13

• excellent hygiene
• maintaining effective SO2 levels
• keeping pH levels low
• treat affected wines with DMDC, Velcorin, which inactivates Brett