Hessian, apes & peacocks

I’d like a dollar for every time I’ve heard a send-up of the language used by wine tasters. The unenlightened delight in lampooning any suggestion that wine could smell or taste of fruit, vegetable, flower, herb or spice. Even a hero of mine, Michael Leunig, had a go. He once penned a cartoon of a wine-taster sniffing a glass and intoning: “Mintiness with peaches and strawberries, a chocolate smokeyness with leathery insinuations… hessian, apes and peacocks… and a faint, elusive yet startling aroma of wine!”

It is very easy to make fun of the language of wine. However, I’m sorry to prick the balloon, but the lampooners are the ignorant ones. Wine does indeed smell of other things in nature, and that’s because it contains the same chemical compounds that comprise the fruits, vegetables, herbs and spices of which its scent reminds us.

I’ll give you proof. And here I’m calling on reinforcements. Dr Leigh Francis is research manager, sensory, at the Australian Wine Research Institute and probably knows more about this subject than anyone else in the world.

Sauvignon blanc is the most popular wine of all at present. It’s often described as smelling/tasting like tropical fruits and vegetables, especially capsicum and asparagus. Says Francis: “Tropical fruits and especially passionfruit are given their characteristic aromas by thiols – sulfur containing compounds – and they’re also in box hedges.” It sometimes smells like tomcat’s pee: objectionable up close, but at a distance it smells like passionfruit, which is more appealing. All contain the same thiols. You may have heard sauvignon blanc described as smelling like cat’s pee on a gooseberry bush?!

An important aroma found in cabernet sauvignon and sauvignon blanc when grown in cool climates is isobutyl methoxy pyrazine. It is also present in capsicum and asparagus. No wonder we use those words to describe the wine. And pardon me for mentioning it, but it’s also likely to be the compound responsible for the smell in your urine after you’ve eaten asparagus – but this is unproven as yet.

Peppery cool-climate shiraz is the latest mystery solved – by the AWRI, just last year – and the compound that causes it has been identified as rotundone. And what do you know, rotundone is present in both black peppercorns and cool-climate shiraz.

Pinot noir is often described as raspberry-like, and surprise, surprise: the thing they have in common is beta ionone – which smells like raspberry. Other red grape varieties (cabernet franc?) also have it.

Diacetyl gives the smell of butter and butterscotch and is involved in cheese flavour. It’s commonly found in chardonnay that’s been barrel-fermented and put through malolactic fermentation. Yeast fermentation produces some diacetyl but malolactic produces even more. No surprise that the confectionery industry uses diacetyl to flavour butterscotch lollies.

Gewurztraminer is one of the most pungent and easily identified grape varieties. It’s given its distinctive aroma by cis rose oxide. This monoterpene was originally identified in rose petals, and is also found in Turkish Delight and lychees – both names often used to describe gewurztraminer wines.

On the subject of monoterpenes, one of them, linalool, is found in both riesling wine and in citrus fruits and flowers, so that’s why riesling wines are often described in terms of citrus fruit and/or flowers.

While we’re talking about flowers, it’s not only aroma that provides a natural link between flowers and wine. Color does too. Some of the colouring pigments (anthocyanins) found in red grapes and wine are named after common decorative flowers, and I’m sure you can work out where delphinidin, peonidin and petunidin come from.

Banana is a very common smell in freshly fermented young white wine, irrespective of grape variety. That’s because both are high in amyl acetate, an ester formed during fermentation but which eventually dissipates. “Yes, it is yeast derived,” says Francis, “and not from the grape. But it is formed by yeast acting on grapejuice.” This gives it a kind of legitimacy for our discussion.

So far I’ve mentioned only primary aromas and flavours, but there are also many secondary characters that have a resonance elsewhere in nature. Oak-matured wines, red or white, are often described as having a vanilla aroma. It’s because vanillin is found in oak wood, and of course it takes its name from vanilla pods. Also found in oak is a coconut aroma caused by a compound called oak lactone. “The flavour of coconuts is largely derived from lactones,” says Francis.

And some aged white wines (especially riesling) can have a kerosene character. That’s TDN (trimethyl dihydro naphthalene). It’s a hydrocarbon, and as Francis says, diesel and kerosene are full of similar compounds.

Getting back to the grassy or vegetal group of smells, which are very common in wines, especially whites such as Margaret River semillon, the smell of cut-grass is hexanol, which is also present in wine. Some of these compounds are most commonly found in certain regions and certain vintages, eg. the 2008 Hunter Valley semillons – from an especially wet year – are very grassy, perhaps due to high hexanol levels.

And finally the blackcurrant flavour of cabernet. It’s due to dimethyl sulfide (DMS). It’s a curious compound. “If you spike DMS into any red wine it gives a blackcurrant character,” says Francis. “And DMS is found in blackcurrants and their cordials. There are probably other compounds involved in blackcurrant too, but DMS is certainly one of them. If you have too much it can smell unattractive, like cooked vegetables. But at low levels, or at a distance, it’s attractive.”

Next time someone takes the (cat) piss out of you when you’re being verbose about wine, be well armed with the appropriate chemistry. It’s pretty hard to argue with.

First published in Gourmet Traveller Wine – Jun-Jul 2009.

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