Top wine faults and what to look for

Patrick Materman of Brancott Estate in Marlborough recently held a wine fault seminar in Hong Kong. Here, we roundup some of the most common causes of wine taint and how to identify them.

Hong Kong’s hot, humid, wet and sunny weather conditions (sometimes occurring all at once) is every wines’ nemesis when it comes to long-term storage but sometimes wine faults can occur during the winemaking process or in shipping which are only uncovered at the point of opening the bottle.

During the 2016 Cathay Pacific Hong Kong International Wine & Spirit Competition, VIP international wine judge, Patrick Materman of Brancott Estate hosted a seminar with Debra Meiburg MW to educate Hong Kong’s wine trade on the top faults affecting wine – Talking Taint: Faulty & Spoiled Wine.

“We as an industry need to be better at this – I’ve tasted many wines with faults over the years,”  said Meiburg.

“Winemakers are trained to look for faults,” said Materman. “Some people, however without this training have a natural ‘blindspot’ because wine faults are not always obvious. Sometimes descriptors can match faults and not all faults are real ‘faults’.

“For example, tartrate crystals that form in unfiltered wines under cold stablisation just need to be decanted. Consumers are often worried that the glass has broken somehow so being able to explain what they are is very important.”

So what exactly can you look out for in a suspected faulty wine?

Patrick Materman has the answers…

Secondary fermentation 

The presence of volatile acidity can make wine smell of nail varnish (or vinegar)

How: Caused by yeast, lactic acid bacteria or acetic acid bacteria (volatile acidity), faults normally occur in natural or low-intervention winemaking (i.e. minimal sulphur dioxide usage) when the wine is mistakenly bottled with a few grams of residual sugar and then re-ferments.

What to look for: Cloudy, hazy or wine that is ‘spritzing’ when it shouldn’t be. The wine suppresses its fruit and gives yeasty characters. In the case of acetic acid bacteria/volatile acidity, there will be a pronounced vinegar or ethyl acetate (nail polish) notes.

Heat damage

Good for our Vitamin A, but sunlight and high heat is perilous to wine

How: Happens as a result of of heat unstable proteins in the wine which denature and precipitate as the wine is warmed – above 80F (26C) – and then literally starts to cook with irreversible damage.

What to look for: Cloudy wines. In extreme cases, the cap has been pushed off the top of the bottle and the bottle has leaked. Corks that have expanded in size or are cracked. The wine will taste very definitely off, or burnt.  

Oxidation

Just like apples, wine is also susceptible to oxidation

How: As bottles age or if they are subjected to intense heat, the corks weaken which allows oxygen to get into the bottle and interact with the compounds.

What to look for: In white wine, the colour will darken to amber and then eventually brown. In red wine, the purple/red hues change to brown/brick hues.  There will also be sherry-like flavours or aldehyde/nutty characters.

Cork taint

Corked wine will smell distinctively of a drenched doggy

How: Caused by 2,4,6 trichloroanisole (TCA) or 2,4,6-tribromoanisole (TBA) which occurs when a tainted cork comes into contact with wine and can happen in the production process.

What to look for: Distinctive musty/mouldy aroma, suppressed fruit. Common complaints include wet dog, mushroom,  or dank earthy notes.  Mousecage-like flavour on palate. Cork taint is one of the most well-known of wine faults and often wine is described as being corked when It isn’t – it will definitely be obvious if a wine is corked! 

Reduction

While not always a bad thing, an overly reductive wine can smell of a struck match

How:  When a winemaker limits the amount of oxygen a wine has exposure to, technically to preserve the fresh, fruit notes.

What to look for: In the presence of volatile sulphur compounds – mercaptans – there’ll be a whiff of rotten eggs (from hydrogen sulphide) rotten onion (disulphides) and canned corn or tomato sauce (dimethyl sulphides).  Also  a distinct aroma of rubber or a struck match.

Brettanomyces

The presence of Brettanomyces can give off a distinctly farmy note – as can some aged Burgundy

How: Brettanomyces is a slow-growing yeast which proliferates under warm cellaring conditions, low sulfur dioxide levels coupled with high wine pH and old oak.

What to look for: A smell of barnyard or Band-Aids (plasters) rotten meat, sewer gas and burnt beans.