What's Wrong With This Wine? Learning to Read a Glass — Through the Bad Ones: Part 1

Some of the most instructive moments in my wine education came from bottles I didn’t enjoy at all. A moldy Cab Sauv. A lunch wine that smelled like nail polish remover. A winery that reeked of rotten eggs before we even walked through the door. At the time, I didn’t always know what was happening. Now I do. And that knowledge has made me a better taster, a more confident customer, and a more thoughtful student of wine.

The nose is your most important wine assessment tool. Even when what it’s telling you is deeply unpleasant, the aromas and flavors in a glass are clues to what happened during the wine’s making.

Here are some of the faults I’ve encountered over the years, and what I’ve learned from them.

Cork taint: The moldy bottle I almost convinced myself to drink

Aromas: mold, wet cardboard, damp basement

My first encounter with cork taint was early in my wine life, and I didn’t recognize it for what it was. We’d picked up a bottle of Cabernet Sauvignon from a winery in Walla Walla, Washington. When we opened it, Katie wisely took one sip and put her glass down.

I, having never tasted an aged red wine, stubbornly suggested that maybe this was what aged Cab was supposed to taste like. I soldiered on through a glass, trying to convince myself that I liked it. But eventually, I had to admit that it smelled and tasted unmistakably like mold.

Since then, I’ve come to understand how common this fault really is. The culprit is a compound called TCA (2,4,6-trichloroanisole) which forms when chlorine compounds (like from cleaning or pesticides) react with certain molds present in cork. Even very small concentrations are enough to replace a wine’s pleasant aromas with that musty, wet-cardboard quality. Estimates put corked bottles somewhere from 3-5% of all natural cork-sealed wines, though improved testing and treatment methods are bringing that number down.

Cork taint happens. But how a winery or other retailer handles it matters enormously. We once bought a case of Pinot Noir from a Willamette Valley winery we loved. One bottle was corked. I called to let them know, and even though weeks passed before I could make it back, they replaced it. We bought more wine. On the other end of the spectrum, a Lodi winery we’d belonged to for four years included a corked library bottle in one of our shipments. I called. I emailed the wine club manager. I heard nothing. I cancelled the membership.

The lesson isn’t lost on me now that I work at a winery. A faulty bottle isn’t just an inconvenience to the customer. It’s a test of trust. The winery that replaces it without question understands that its reputation, and sometimes the whole region’s reputation, may be on the line.

Volatile acidity: The lunch wine we quietly left in our glasses

Aromas: vinegar, nail polish remover

A family member once invited us over for lunch and, knowing we love wine, opened a bottle from a winery near their home in Washington State. It was a generous and thoughtful gesture. But the wine smelled overwhelmingly of acetone. It was not subtle. It was the wine’s dominant character.

I didn’t have the vocabulary for it at the time, but what we were experiencing was volatile acidity (often abbreviated to VA) at fault levels. All wine contains some acetic acid (the compound that gives vinegar its punch), and a modest amount is considered normal, even desirable for complexity. But when oxygen isn’t carefully managed, when sulfur dioxide isn’t used correctly or at the right times, or when hygiene lapses allow acetic acid bacteria to proliferate, that acidity can climb to levels that overwhelm everything else. Add ethyl acetate (a related compound) to the mix and you get that solvent, nail-polish-remover quality.

Understanding this fault helped me appreciate just how many decisions go into preventing it: thoughtful fruit sorting, meticulous sanitation, diligent oxygen management, and judicious use of sulfur dioxide.

Reduction: From toasted marshmallow to rotten eggs

Aromas: struck match, smoke, rotten eggs, sweet corn

This is a fault that can be complicated, because at low levels it can be genuinely beautiful. One of my favorite wines of last year was a Willamette Valley Chardonnay with just a whisper of reduction — a smoky, toasty quality that reminded me of the caramelized outside of a perfectly roasted marshmallow. Delicious. Clearly intentional.

But the conditions that create that pleasant quality can spiral very quickly into something far less appealing.

We were visiting a winery in Paso Robles, a place we’d liked enough on a previous visit to join the wine club. It was just at the tail end of harvest. Before we’d even stepped inside the tasting room, we were hit with an overwhelming smell of rotten eggs. It was impossible to ignore. Other visitors seemed to be politely pretending not to notice. At first we wondered if someone nearby had... an unrelated problem. But the smell persisted through the entire visit and made the wines very difficult to assess or enjoy.

I now know that the most likely culprit was stressed yeast during fermentation. Yeast need nitrogen to do their work of converting grape sugars into alcohol. When they’re starved of that essential nutrient, or stressed by heat or other pressures, they produce volatile sulfur compounds as a byproduct. Reduction can also develop during aging if wine sitting on its lees isn’t given enough exposure to oxygen. The takeaway, as I understand it: take care of your yeast.

Reduction has another face I discovered only recently. Playing the board game included with the Aromaster Professional Sommelier Wine Aroma Kit, I encountered an aroma card labeled “sweet corn” and thought: surely that’s not something that actually turns up in wine.

Then, the very next weekend, we visited a winery where more than one white had that exact aroma: starchy, unmistakable, canned sweet corn. It’s caused by dimethyl sulfide, another reductive compound that forms when yeast are deprived of oxygen or nutrients. Once you learn to identify it, you can’t unknow it.

Continue to Part Two, where we encounter a bottle of Champagne that smelled like a cheese course, a rosé full of mysterious crystals, and a Pinot Noir that smelled like fish.