Understanding Wine Faults: A Comprehensive Guide to Types, Aromas, Compounds, and Causes by Csilla Kato, D.W.S., A.I.W.S, Winemaker, Instructor

Understanding Wine Faults: A Comprehensive Guide to Types, Aromas, Compounds, and Causes by Csilla Kato, D.W.S., A.I.W.S, Winemaker, Instructor

Wine faults – a topic that always creates a lively discussion among enthusiasts. Beauty is in the eye of the beholder, but in the case of wine, it will likely be your nose or palate that discerns if the precious liquid in your glass is indeed flawless or not.

A wine fault is a sensory-associated element in wine that is generally considered unpleasant and can make a wine undrinkable. It may have a chemical or microbiological origin, and some faults can be traced back to bad viticultural or winemaking practices, or inadequate storage conditions. These can include poor hygiene at the winery, improper oxygen exposure (either too much or too little), improper use of sulfur dioxide, improper stabilization, uncleaned oak barrels, inferior corks, wide temperature fluctuations during storage, and even dirty glassware.

Wine faults exist along a broad scale of intensity, and individual sensitivities can vary widely – what may be fine for one person can be undrinkable for another. Some wine drinkers find that low levels of fault-causing compounds enhance the complexity of a wine. For example, some people enjoy the medicinal aroma of Brettanomyces in a northern Rhone Syrah or a reductive struck match aroma in white Burgundy, while others strongly dislike those flavors. 

Either way, once an off-aroma reaches a sensory threshold that takes away from the enjoyment of a wine, and one learns to recognize them, there is no way back: with knowledge comes responsibility, and you will forever be the one to check the wine poured at your restaurant table.

The last few decades have brought a vast improvement in winemaking technology and the scientific understanding of wine, which has made many faults less common. However, the following problems are still encountered from time to time:

 

Fault

Aroma

Compound(s)

Cause

Cork taint

Musty basement, moldy, dull fruit, wet cardboard

2,4,6-trichloroanisole (TCA), 2,4,6-tribromoanisole (TBA)

Contaminated cork during the cork growth and harvest process, chlorine cleaning products used during winemaking

Brettanomyces

Medicinal, cardamom, horse barn/blanket, band-aid, manure

4-ethylphenol (4-EP), 4-ethylguaiacol (4-EG), 4- ethylcatechol (4-EC)

Brettanomyces yeast growth

Acetaldehyde

Green apple, brazil nut, wet paint

Acetaldehyde

Microbial contamination, poor yeast health, oxidation

Volatile acidity (VA)

Vinegar, nail polish remover

Acetic Acid, Ethyl Acetate

Spoilage bacteria, wild yeast, microbial contamination

Reduction

Mushroom, radish, olives, rotten egg, onion, cooked cabbage, canned corn, burnt rubber, struck match

Dimethyl Disulfide, Hydrogen Sulfide, Ethane Thiol

Lack of oxygen during winemaking

Mousiness

Mouse cage, stale popcorn, dog breath, corn nuts — exists only on the palate and can’t be smelled

2-acetyltetrahydropyridine (ACTPY), 2-ethyltetrahydropyridine (ETPY), 2-acetylpyrroline (ACPY)

Spoilage bacteria and/or yeast

Very low sulfur dioxide additions

Smoke Taint

Smoky, ashy, charcoal

Guaiacol

Contamination in the vineyard during a fire

                                               

Armed with this knowledge, the question remains: what should you do if you encounter one of these faults? If you purchased the bottle at a wine store, they should have a written policy on returns – some do not accept open bottles, some do. Naturally, you should never return a bottle with more than a glass or two missing. In most cases, especially if you purchased the bottle at an independent retailer, the store will take back a bottle and will be reimbursed by the distributor or producer, so it’s always worth asking.

At a restaurant, if you feel the wine has something wrong with it, don’t be upset — just respectfully tell your waiter. The sommelier usually smells and tastes the wine to confirm and will open another bottle for you. The waiter or manager could do the same if the restaurant does not employ a sommelier. Either way, if the wine is flawed, there should be no pushback, no questions asked. Sometimes if the bottle is rare, really old or exceptionally high value, staff  may try to explain their way out of it, saying, “it just needs to open up” or “those are just tertiary aromas,” etc. But you should calmly and firmly stand your ground, and request a new bottle. 

However, if the wine is technically sound but is just not to your liking, it might be a different story. Some restaurants allow for small tastes of their by-the-glass wines to help avoid pouring you a full glass of something you don’t like. Barring that, you still could ask for another wine, but you will need to explain your decision a bit more. This scenario can offer an opportunity both for the sommelier to learn about how people react to that wine, and for you to understand your tastes better, but restaurants working on slim profit margins may not always have the ability to work with you in these cases.

Like in any area of life, politeness and clarity go a long way. The staff at the restaurant will want you to leave happy and satisfied, and at the end of the day, you should have the dining experience you paid for. 

As wine faults have become less common overall, experiencing one can be a novel learning opportunity for any lover of wine. Don’t be afraid to speak up if you come across a faulty bottle.

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D.W.S., A.I.W.S, Winemaker, Instructor

Csilla Kato

Csilla was born and raised in beautiful Budapest, Hungary, and was bitten by the wine bug during high school when she helped with regular tastings at her brother’s wine shop. After a short stint in law school, she changed her focus and spent five years earning her Masters degree in Fermentation Science and Post-Harvest Technologies. Right after graduation she had the opportunity to work and travel and landed a harvest in Sonoma, California. Csilla worked with Zinfandel, Cabernet, and Chardonnay while learning the process of winemaking first hand in the famed Ravenswood Winery.
After her first harvest, she was hungry for more and went on to take part in harvests in Italy, Hungary, and New Zealand, as well as Napa. She has spent years working in winemaking labs analyzing the myriad of aspects that make wine great while also making great wines along the way. Since 2007 she has been with Beringer Vineyards, where she began as an Enologist and today is an Associate Winemaker with a few labels under her supervision. Tramping around vineyards, tasting fermentations at various stages and assembling final blends are some of her favorite parts of being a winemaker. Csilla also enjoys sharing her passion and knowledge about the wine industry with those who care to know.
She holds her Level 4 Diploma with the prestigious Wine & Spirit Education Trust and relishes the opportunity to educate new students at Napa Valley Wine Academy.
Married to an amazing brewer, who has taught her to appreciate great beers, she is a mother of two and spends most of her free time enjoying watching them grow.