Skip to main content

A common question in wine appreciation classes is how you know when a wine has gone bad. Bad in this case means faulted as a result of poor storage, microbial contamination, or a production mishap. Bad meaning spoiled wine, not a well-made cabernet or pinot grigio, for instance, that simply isn’t pleasing to your taste.

Better understanding of the science behind grape growing and winemaking means that faultless wines are produced on a consistent basis. They might be simple or bland, but they’re squeaky clean when it comes to wine chemistry. But there may be times when you take a sip in anticipation of a plummy and cedary flavour of a favourite cabernet only to be greeted by a musty or vinegary taste that’s a shock to your system.

The best appraisal of a wine’s character is a moment of critical evaluation. Think of the ritual of being presented with a wine at a restaurant. The whole point of being shown the bottle’s label and taking that first taste is to ensure the wine is correct. That it is, in fact, the bottle you selected from the wine list and it tastes as it should. By inspecting the colour, assessing the aroma, and evaluating the flavour, you have a moment to focus on anything that seems at all unexpected or unpleasant before accepting the wine. Use the same technique at home to test your wine before pouring a full glass.

Two Common Wine Faults

Cork taint (Corked)

What it looks like: Doesn’t influence a wine’s colour

What it smells like: Damp cardboard, musty, mouldy, wet dog

Cork taint is a potential fault facing all wines sealed with natural cork, although there are rare instances where the musty taints are environmental from a winery’s cellars. A compound called halonanisole 2.4.6.-trichloronanisole (TCA for short) can contaminate wine with musty basement aromas and flavours. When the damp/mouldy smell is pronounced, it’s easy to spot a corked wine. In smaller doses, however, it simply robs the wine of its fruity aromas and flavours, making it appear less fresh. If you haven’t had that wine before you might not spot the fault and simply think it’s a poorly made wine. Twenty years ago, before usage of screwcap and other TCA-free closures became widespread, industry standards suggested an incidence rate of greater than 10 per cent. Today it is less than 5 per cent.

Oxygen / Cork failure (Oxidized)

What it looks like: Less vibrant brown tones; white wines are darker than expected; reds are more garnet/brick coloured

What it smells like: Honey, coffee, caramel, nutty, applesauce

What it tastes like: Lacks fresh, fruity flavours, bitter, drying finish

Oxygen can adversely affect or improve the quality of a wine at various stages during fermentation, maturation and storage (especially if the closure doesn’t provide an airtight seal). The more oxygen interacts with a wine, it will cause it to lose freshness and its fruity character. In some instances, such as mature Gran Reservas red wines from Rioja, this is a desirable and welcome character. But if a 2022 sauvignon blanc from Marlborough has a dark golden colour and smells like hazelnuts and coffee, it’s safe to assume that’s not what the winemaker had in mind. A wine that’s gone bad from being left opened for too long will also show the ill effects of oxygen exposure. If you leave a bottle for too long (it can happen), smell it before dumping it down the drain to get a sense of the nutty and sour notes that have replaced the usual fruity flavours so you can better understand the effects of oxidation.