How do you know when a wine has ‘gone off’ – and what should you do about it?

For some reason, drinking wine always seems to come with apologies – and I’m not just talking about the morning after. When I worked in retail and hospitality, customers regularly approached me to say things like “I’m sorry, I don’t really know what I like, nor do I have any knowledge of, or understand anything about wine”.

How is something that is supposed to be pleasurable tangled up in so much pressure and pretence? If you combine this with the absolute certainty that you will, as a wine drinker, encounter faulty wines, I wonder – will you have the confidence to do something about them?

The ultimate aim of drinking wine is your own enjoyment. It’s likely that you’ll have parted with your hard-earned cash when enjoying a bottle in a restaurant, bar or something you’ve picked up to quaff at home. As such, it’s vital that you like what you drink. Of course, there will be instances when something isn’t quite to your tastes: perhaps an overly oaky chardonnay, or a way too tannic, lip-puckering cabernet sauvignon. That’s just part of the process of finding the style you enjoy – but there’s never a reason to endure faulty wine.

At a recent lunch, I ordered a glass of English sparkling wine – it arrived in a beautiful flute with a fine bead of bubbles dancing in the glass. On the nose, it was a little dull, but I thought it might just be too cold. I took one sip and knew it wasn’t right. I hate this moment: I know I have to say something, but my initial reaction is always one of discomfort. I called the sommelier over, and said, “I’m sorry” – I don’t know why I was apologising – “but I think this wine is corked. Would you mind tasting it?”

It was simple, direct and polite. He did, and he confirmed what I knew. He popped a fresh bottle and gave me another glass, and then... the same thing happened. I was mortified, and started doubting myself, but I knew it tasted wrong. The sommelier tried it, agreed with me and bought me a glass of champagne, on the house.

The situation was handled immaculately – but it might not always be that way for you. It’s important to know what to look out for, so that you can be confident when encountering wine that isn’t quite right.

So what are the most common faults to look out for? In the case of corked wine, we’re not talking about pieces of cork floating in the glass, as many people think. Rather, when a wine is “corked”, it refers to the contamination of the wine by the chemical compound 2,4,6-trichloroanisole, or TCA, which is found on the cork itself.

The compound can be present to varying degrees, and is best identified as something that smells and tastes a bit like soggy cardboard, damp dish cloths or wet dog. I always suggest to friends if they’re out and one of them has identified a corked wine that they ask the others to smell and taste it too. While not particularly pleasant, this process helps your nose learn what to look out for, so you’ll be able to spot it again in the future.

Another common fault is oxidised wine, especially if you’re buying something by the glass. Whilst this can occur before a bottle has even been opened, it’s more common in a wine that’s been open too long. If it’s a white wine, it might take on a darker colour and taste a bit like a sherry you’ve found at the back of your nan’s drink cabinet.

In a similar vein to oxidised wine, it’s always good to be alert to faults if you’re ordering sparkling wine by the glass. If it’s not lively and fresh when it arrives, you can simply say so and that you’d like a replacement. Nobody should pay to drink a flat glass of bubbles, regardless of it it’s prosecco or champagne. If an establishment is serving any wine by the glass, the expectation should be that it is served at the optimum condition. I would never question a customer if they weren’t happy, and any decent restaurant, bar or pub should do the same.

And then there are “mousey” wines – or, more accurately, microbial-infected wine. Bacterial microbes naturally form in wine, and in general, are actually very good for you. However, sometimes they can overgrow and make the wine taste “off”. You might encounter this problem with wines that haven’t been treated with sulphur dioxide – the smell and taste might remind you a bit of your primary school’s gerbil cage.

As with everything, some people are more sensitive to faults – if you can’t taste them, then that’s great. But if you are in any doubt, you should absolutely have the confidence to speak up and to feel absolutely zero guilt in doing so. Trust your instincts.

Wine shops, supermarkets, restaurants, bars and pubs all know that faults occur, and should be ready to offer you a replacement for your purchase free of charge. If they don’t, I’d consider taking my business elsewhere.

Just remember, you never need to apologise for rejecting a spoiled wine – which is a piece of advice I sometimes need to remind myself of, too.

Rosamund Hall (DipWSET) is a freelance writer and wine expert