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No-Fuss Guide · No. 25

How to tell if wine has gone bad: the smells that give it away, and what only looks like a fault

Use your nose, before the first sip. A mouldy smell is the cork. Vinegar or nail polish, bacteria. Bruised apple and a colour turning brown, too much air. Egg or a struck match, too little air, and that one usually goes away in the glass. Crystals at the bottom and sediment in an old red are not faults. And a sealed bottle carries no expiry date: Brazilian law exempts wine from printing one. To make it last, lay it down and keep it away from heat.

Does wine have an expiry date?

Not on the label. The rule from Anvisa, Brazil's health agency, for labelling packaged food (RDC 727, from 2022) lists in its annex what is exempt from printing an expiry date: wines, liqueur wines, sparkling wines and any alcoholic drink at 10% alcohol or more. That is why the bottle shows a lot number, not a “best before”.

No date does not mean it lasts forever. Most wines are made to be drunk young, close to the vintage on the label; only a minority improves with age (wines for ageing). What shortens the life of a sealed bottle is heat and light, and the house covers that below. Once opened, it is another story: how long an open bottle lasts.

The smells that give a fault away

Smell the glass still, then swirling. The list below follows what the Australian Wine Research Institute (AWRI) describes for each fault.

The cork: mould that wipes out the fruit

The most common culprit has a long name, 2,4,6-trichloroanisole, or TCA. The AWRI describes a distinct musty, mouldy smell, and notes that some people pick up TCA below 1 nanogram per litre: less than a billionth of a gram. It almost always comes from the cork, but it can also form in oak.

Vinegar and nail polish

Every wine has a little volatile acidity; more than 93% of it is acetic acid, the acid in vinegar. It usually starts to get in the way above 0.7 grams per litre. Its cousin, ethyl acetate, smells of nail polish remover when there is too much. Both come from bacteria working with air.

Oxidised: too much air

First the aroma goes dull, then comes cardboard, straw, hay, and finally the smell of Sherry and Madeira. White wine suffers more than red, which has more natural defence (the phenolics, which come from the skins). In Sherry, air is the style and the whole point; in a young everyday white, it is a fault.

Egg and struck match: too little air

This is the one you can fix. A mild struck-match or sulfur smell right after opening usually goes away with air: swirl the glass hard and wait a few minutes, says Decanter, and the fruit shows up. If the rotten egg, cabbage or rubber stay, then it is a fault.

Lightstrike

Light activates a vitamin in the wine itself (riboflavin) and, through a chain of reactions, sulfur compounds form. In Dozon and Noble's 1989 test, with two fluorescent lamps 35 cm away, still and sparkling whites in a clear bottle already had the fault after just over 3 hours; in green glass, after 18 to 31 hours. A sunny shop window is far worse than a lamp. White and sparkling wine in clear glass: buy from the back of the shelf and keep it in the dark.

The bottle that got hot

The AWRI's technical note on heat and light pulls together what research found: stored at 30 °C, wine showed faults and lost quality within 12 months; above 40 °C, it changes colour and taste in a matter of days. The rule of thumb: a place that goes above 25 °C for long periods, or 40 °C for short ones, can spoil the bottle. The recommendation is to store it between 15 and 20 °C, away from the stove, the window and the car boot.

The sign you can see from outside is a cork pushed up or wine seeping down the neck: the liquid expanded in the heat. The AWRI warns that this does not prove the wine is spoiled, only that the bottle got hot. Open it and smell.

How to store a sealed bottle: lying down or standing up?

A bottle with a natural cork: lay it down. The same AWRI note repeats the classic advice: store it with the cork touching the wine, somewhere cool (15 to 20 °C) and dry. A screw cap has no cork to worry about, so the reason for lying the bottle down does not apply.

More than the exact temperature, what matters is that it does not keep going up and down: the AWRI asks for a place with little change in temperature and humidity. In practice, a cupboard away from the stove, the window and the sun, and never the car boot. And the fridge? For a few days, fine. For months, some say the compressor's vibration does harm, but the AWRI itself says it found no study on it.

What looks like a fault but is not

Crystals at the bottom or stuck to the cork. These are tartrate crystals: the grape's natural acid combined with potassium, which crystallises in the cold. Decanter sums it up: they do not change aroma, taste or quality. More carefully made or age-worthy wines often skip the step that prevents them, because it can strip flavour.

Dark powder in an old red. It is sediment, tannin and colour that dropped out over the years. It tastes bitter, so decant it or pour slowly and leave the last bit in the bottle.

Screw cap. It is not a sign of cheap wine, and there is no cork to cause the mouldy fault. See screw cap in the glossary.

I didn't like it. A wine you did not enjoy is not spoiled: that is taste. Found one you like? Go for it, and good for you for finding out what you like.

You opened it and it was bad: now what?

In a restaurant, that little sip the waiter pours first is the moment to smell. Mould, vinegar or egg that does not go away: say so, and ask them to smell it too. At home, keep the bottle with its cork and the receipt, and talk to the shop. And a wine that only went past its best from air still works for cooking, as the open-bottle guide explains.