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The science behind wine’s odder flavours


Posted in: Wine Market News

Tagged: Wine Culture

For the casual enthusiast, tasting wine is very much about identifying fruit and floral flavours, both of which are arguably the bedrock of wine tasting. However, as more seasoned aficionados will tell you, every wine is a gateway to a host of other flavours and aromas if you know where to look (or taste).

Indeed, sommeliers and experts spend years honing their tasting skills in order to identify a myriad of aromas, many of which – on the face of it – may seem a little unappetising. Leather, cooked cabbage and clove don’t stand-out as particularly appealing drinkable flavours, for example. But these notes nonetheless play an important role in creating a wine’s overall profile, and indeed the presence or absence of some of them can mark the difference between a critic favourite or flop.

Unlike a wine’s standard fruit flavours which stem largely from the grape, however, these odder aromas are the result of chemical processes and compounds created during winemaking. Here’s what to look out for during your next tasting.



Smells like: clove, cardamom, first aid equipment, plasters, sweaty leather saddles

Brettanomyces – also known as 4-Ethyl Phenol (4-EP) and 4-Ethyl Guaiacol (4-EG) – is a wild yeast often present in red wines made with rustic winemaking methods. It’s responsible for some fairly pungent aromas that many consider a fault, particularly as it was more common before we had the technology to properly clean winemaking equipment. That said, some people are big fans of the woodsy, leather-like aromas that occur in wines where lower levels of Brett are present.


Reduction (sulphur compounds)

Smells like: mushroom, green olive, rotten egg, cooked cabbage, onion, burnt rubber

Reduction – more commonly known as sulphur – is a combination of dimethyl disulfide, dimethyl sulfide, hydrogen sulfide and ethane thiol. This occurs naturally in wine as a result of fermentation, even without sulphite additives. At a low level, reduction can add a mushroom or green olive smell to wine, which many have accepted as positive traits. Additionally, reduction is noted for adding a subtle creaminess to the texture of a wine. At higher levels, however, reduction can be responsible for unpleasant aromas of rotten egg, cooked cabbage or burnt rubber, and is subsequently considered a fault.


Volatile acidity

Smells like: vinegar, sharp berry, nail varnish remover, paint stripper

Volatile acidity – acetic acid and ethyl acetate – occurs when a wine is exposed to too much oxygen during the winemaking process. At higher levels, this can create unpleasantly-sharp flavours, such as vinegar or even nail varnish remover, and is rightly considered a fault. At lower levels though, this volatile acidity can add favourable fruity-smelling cherry and raspberry-like flavours. Wines with long fermentations such as Ice Wine and Barolo tend to accumulate higher levels of volatile acidity.



Smells like: candied apples, rotten fruit, nuts, wet paint

Acetaldehyde – also known as ethanol – occurs naturally in wine through yeast activity or oxidation and is actually a type of poison, albeit one that is present in wine in very small amounts (dry whites, for example, have around 30-80 parts per million). The compound plays a particularly important flavour role in Sherry and other oxidised wines (which typically have 300 parts per million), creating pleasant fruity notes akin to candied apples. It’s also responsible for a ‘tang’ on the mid-palate and finish. At higher levels, though, acetaldehyde can create aromas of rotten fruit, pungent nuts and even wet paint.

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