15.4 Faults

Question 1

Why might wines be cloudy or hazy?

Answer 1

• growth of yeast or bacteria
• failure to filter adequately (e.g. pumping wine at too high a pressure through a depth filter so that some unwanted molecules go through the filter).
• unstable proteins remaining in the wine, causing it to go hazy after the wine has left the winery
• protein haze where fining is not effective
• wrong type of fining agent has been used
• wine has been over-fined
  Prevent
• better hygiene in the winery
• pre-bottling chemical analysis
• filtering wine to remove yeast or bacteria before bottling
• fine correctly and conduct analysis after fining

Question 2

What are tartrates?

Answer 2

Colourless or white crystals in the bottom of bottle that can be mistaken for fragments of glass
- can be seen as a fault by consumers
- knowledgeable drinkers know that this is a natural process triggered by low temperatures and is completely harmless to health and wine quality
prevent
- inexpensive and mid-priced wines
- stabilised before release from the winery

Question 3

Why may visible bubbles or spritz in wine be seen as a fault?In what types of wines would visible bubbles or spritz not be considered a fault?

Answer 3

• If accompanied by cloudiness, it would indicate unwanted re-fermentation in the bottle
• A failure to stabilise and clarify/filter the wine adequately
• Wines that purposely include a low level of spritz
  (e. g. Muscadet sur lie or Vinho Verde).
• Some inexpensive and mid-priced white wines will have a small amount of CO2 added before bottling to preserve and enhance freshness.

Question 4

What is the effect of cork taint on the wine?

Answer 4

• Associated with a very unattractive, mouldy, wet cardboard smell
• Reduces the fruit character
• Shortens the finish

Question 5

What is oxidation (fault)?

What can cause oxidation post bottling?

Answer 5

Excessive exposure to oxygen either in the winemaking process or once in bottle or other container
cause
- faulty bottling
- poor quality corks or plastic closures
- simply keeping wine for too long if it is not of a quality to age

Question 6

Describe an oxidized wine (fault).

Answer 6

• wine becomes prematurely brown in colour
• loss of primary fruit
• vinegary smell

Question 7

What is volatile acidity?

Answer 7

• All wines have volatile acidity
• Excessive amounts give a pungent smell of nail varnish and/or vinegar
  cause
• activity of acetic acid bacteria
• inadequate levels of SO2
• excess exposure to oxygen
  reduce threat:
• sorting fruit to exclude damaged grapes
• scrupulous hygiene in the winery
• keeping vessels topped up
• careful racking (to avoid excessive exposure to oxygen)
• maintaining adequate SO2 levels

Question 8

What is reduction?

Answer 8

• associated with sulfur-like odours that range from onion to rotten eggs
• caused by high levels of volatile, reductive sulfur compounds
• depending on compounds present and levels, can add a layer of complexity or can be considered a fault
  cause
• sulfur compounds can be produced by yeast under stress (due to low nitrogen levels) in the winemaking phase
• near complete exclusion of oxygen during ageing in closed vessels, especially when lees ageing
• when wine is closed with the impermeable type of screw cap
  avoid
• ensuring yeast has sufficient nutrients and oxygen
• ensuring must is at an adequate temperature
• reducing SO2 levels (especially if the closure used allows very little oxygen ingress)

Question 9

What is light strike?

Answer 9

• caused by UV radiation and certain wavelengths of visible light reacting with certain compounds in the wine to form volatile sulfur compounds
• gives odours such as dirty drains
  at risk
• Wines that are left in direct sunlight
• Wines placed near fluorescent lighting (e.g. in retailers)
• Wines packages in clear glass

Question 10

What is Brettanomyces?

Answer 10

Brett is a yeast
produces a range of off-aromas animal/ farmyard

• Fruity flavours are reduced
• Acidity/tannins become more prominent
• Can add complexity to red wines at low levels

prevent
1 .excellent hygiene
2. maintaining effective SO2 levels
3. keeping pH levels low
4. exec MLC asap after alc ferm so that so2 can be added as soon as possible (avoiding exp to oxygen!)

Once it has occurred in a winery, Brettanomyces is difficult to eradicate, especially as wood can host the organism and be very difficult to clean effectively. It can be present in old or new barrels.