We all know the experience; a strange old custom that stands out in the modern dining experience as uniquely formal and stilted

You're in a restaurant. Once the wine has been ordered and the bottle summoned then opened in front of you, a tiny splash of wine is placed gently into your glass, followed by: "would you care to try the wine?" - a passive command more than a question. Suddenly the onus, and pressure, of taste and distinction are placed on you, the humble diner.

In films, the serving of wine is used as a signifier of something cultured and refined in the modern age, often to the foil of those who lack this training, while at the same time lampooning the pomposity of it all. When Steve Martin's character in The Jerk, Navin R. Johnson, is asked by his waiter if he would like another bottle of Chteau Latour 1966, he replies: "Yes, but no more 1966. Let's splurge - bring us some fresh wine, the freshest you've got! This year's, no more of this old stuff!"

Admittedly, I'm quite at ease in this scenario nowadays, but I still worry that I might make a fool of myself, because the person that brought me the wine will invariably know their wines better than I do! However, I remember a time when I never even knew what the purpose of the seemingly archaic ceremony of trying the wine was…

Its function is unclear to many, because we are meant to try the wine and either declare that it is good and we are happy with it, or it is bad and we want another bottle. This has given rise to a myth that we are testing to see whether we like the wine. On this logic, if we were bold enough, we could request another bottle ad nauseum until we find one more to our tastes. Not so.

Rather, this is about checking for one of the many taints and spoils that can ruin wine in the bottle. And wine can very frequently be spoiled, especially if sealed with natural cork. Estimates vary, but some suggest that as many as one in twenty bottles are affected by cork taint.

Of course, as alternative methods of sealing like screw caps and synthetic corks slowly begin to shake off their long-held (and unfair) stigma as déclassé, more and more bottles using these seals are appearing in restaurants. Screw caps are not infallible, but the chances of finding ruined wine within are really small. It makes trying the wine even more excruciating when there's basically zero chance of a problem!

So what do you look for in order to spot a flawed wine? Well, the first point is that you probably don't want to 'look' too hard. Unless you are an expert, this won't give you much info, especially in the dim light of a restaurant setting.

Things like sediment and crystals are usually good signs, if anything including clear crystalline build-up on the wet end of the cork (formed by tartaric acid and perfectly normal). Any 'floaty' bits in wine are invariably fragments of cork pushed out by an over-eager corkscrew, and also quite innocuous.

Equally, in terms of spoiling, you will learn little from taste that your nose won't give you, so use your beak first. Plus, you really look like you know what you're doing if you only nose the wine to try it. Everyone will be well impressed!

When we say a wine is 'corked', this refers to bacterial spoiling (often from the cork, hence the nickname), and this makes the wine smell and taste quite foul, like rotting cardboard, wet dogs, old seaweed and other delightful flavours. While corking doesn't turn the wine into poison, it's much more pleasant to find out it's there by smell than by taste (not to mention less embarrassing - spitting bad wine back into the glass isn't pretty!).

The other big spoiler is air getting in and causing oxidation, which lends wine notes of vinegar and sherry. Interestingly, sherry and wine vinegar are both lovely examples of oxidised wine products, but they are made under control, by professionals. Done by accident, oxidised wine is utterly gross, and again, very unpleasant to discover by taste, so always nose first!

What to do with a bad bottle? If in a restaurant, be brave and go with your convictions; if it stinks, ask your server to check it for you, and invariably, you will be right. If it was from a shop, simply re-cork it and return it, but be sure not to pour the wine away - you'll look like a chancer trying to return an empty bottle, and some merchants have a policy that they will not accept returns for empty bottles.

Phew! Pressure off!

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