The Impact of the Environment on a Wine's Flavour

  • Tuesday 9 June 2009

A hint of minty eucalypt in your Shiraz might be welcome, but traffic pollution or smoke taint? Margaret Rand considers the impact of the vineyard’s local environment on a wine’s flavour

It was in 2007 that Australians discovered a new tasting note. It’s one they’d rather have not known about, but it forced itself on them, and made a lot of wines from affected areas in that vintage well-nigh unsaleable. The note? ‘Smoke taint’. It came from forest fires that spared the vineyards but passed close enough for their smoke to billow over the vines. Was it imagination? The witch-hunting palates of judges seeking yet another way to trip up innocent young wines? In any case, how could a cloud of smoke, passing over and then dispersing, affect the flavour of the wine after fermentation, fining and ageing?

It’s a concern that Australian winemakers are having to confront again, after the horrific fires in Victoria earlier this year threaten to leave a vinous legacy. But to find the answer we need to start elsewhere: with a eucalyptus tree.

It was a beautiful tree, older than the home it sheltered. But it was a eucalypt. And it was close to a vineyard. Its owner hated it. It gave a eucalypt character to the wines, he said. I looked sceptical. I’d heard this before: a bit of winegrower’s folklore. But yes, he insisted, it did. That minty, medicinal character in his Cabernet: eucalypt. The oil vaporises, he explained; it gets on the grapes. So chop it down, I said. But it’s illegal to fell native trees in Australia. A eucalypt in your vineyard is there for life. If you don’t like it, you’ll have to move the vineyard.

In Australia, eucalypts (also called blue gums) are part of the terroir. Just as you plant a vineyard to take account of the prevailing wind, the angle of the slope and exposure to the sun, so you should look at the local trees. You might like the flavour of eucalypt: a touch adds freshness and a minty, floral character to red wines. But too much can be overwhelming. It comes from, not surprisingly, a substance called eucalyptol, also known as 1,8-cineole. If you want to taste a strong version, try Simon Hackett’s Anthony’s Shiraz: this McLaren Vale wine is made from grapes selected for maximum eucalypt effect. If nothing else, it’ll clear your head.

Studies so far have been aimed at establishing whether eucalyptol gets into the wine from the trees, or whether it appears in the wine for some other reason. But the evidence points to the trees. One study for the Australian Wine Research Institute, on a single vineyard in the Yarra Valley, showed that vines within 50 metres of eucalypts had 15.5 microgrammes per litre (a microgramme is one-millionth of a gramme) of eucalyptol in the finished wine; those between 50 and 175m away had just 0.1 microgrammes per litre. The idea that the oil vaporises and gets on to the grapes seems to hold water, too: eucalyptol is found in significant concentrations only in red wines. Sauvignon Blancs, Semillons, Chardonnays and Rieslings have all been tested by the AWRI, and none have even reached the threshold for detectability. This suggests that it’s fermenting with the skins that gives the flavour. But leaves getting into the fermentation vats could also be a route: significantly less eucalyptol is found even in red wines when the grapes are handpicked, and are therefore free of the leaves and other bits and pieces that a machine will let through.

Pungent aromas

Eucalypts, of course, have spread everywhere. You find them in Portugal, Chile, France, Spain – everywhere a plant collector might have sought new species, or a landowner wanted a source of timber, you’ll find eucalypts. But only in Australia are they protected. In other places they’re as likely to be regarded as a weed, and in South Africa they’re worse. Here they’re an ‘invasive alien species’, and you’re encouraged to get rid of them. Some are actually prohibited.

Bruce Jack of Flagstone/Kumala likes the flavour, and points out that it’s not just a question of oil or leaves: the health of the vine is also a factor. ‘The roots of the bluegums compete with the vines for water, and the vines get stunted and weak. It’s a combination of that, and the oil getting on to the grapes. If you run a deep ripper between the vines and the bluegums to cut the bluegum roots, the vines are stronger and the bluegum character is less apparent.’

What, then, of fynbos, the tough, aromatic, native scrub that covers hillsides in South Africa? If gums can flavour wine, why shouldn’t other herbs? Fynbos flavours are a possibility, says Jack, especially if used as ground cover in vineyards. There’s one plant in particular, buchu, which might have an effect: it’s strongly blackcurranty, and was bought by Coca-Cola, Jack says, until a synthetic substitute was developed.

Over in the Douro, another region where the aromas of the scrub permeate the air, David Guimaraens of The Fladgate Partnership has sensed an aromatic, eucalypt note in Ports from a couple of his quintas, but he can’t prove it. ‘I haven’t commented on this before: I’d be locked up as a lunatic,’ he says. ‘But after replanting a vineyard at Quinta de Terra Feita a few years ago we chose to plant esteva (gum cistus) on the embankment separating two blocks.’ Esteva has the most wonderful, pungent aroma: you smell it and you think, yes, the Douro. Guimaraens sometimes finds it in Ports, and clearly would like to find it more often.

Fumes & fires

Javier Ausas would back him up. He’s the winemaker at Vega Sicilia, and insists that the aromas of the herbs and scrub that are interspersed with vines affect the aromas of the wine. Purificación Mancebo, export manager at Vega Sicilia, explains: ‘Grapes have a waxy substance covering the skin called pruina; this can capture aromas from the environment, which are then preserved during fermentation and ageing.’ Suddenly there’s a more sinister side to all this. Mancebo adds: ‘The pruina can capture smoky aromas or lead too.’

No studies, so far as I know, have been done on the effect of traffic fumes on wine flavour. Oddly enough, roads and traffic are not something growers boast about when describing their terroir; but like trees and scrub, they could be said to form part of that terroir. At Vega Sicilia they certainly thought so, when a motorway was mooted nearby, and all their considerable resources were mobilised to stop it. And what of the new motorway planned for Bordeaux? There are several proposed routes for this, all of which affect vineyards to some extent, and all part of the European north-south axis. The new road will carry 20,000 vehicles a day by 2025. It will join the A10 with the A63, bypassing the Bordeaux ring road. The Bordelais growers don’t like the sound of it at all.

Which leads us back to smoke taint. This has been a year of forest fires: not just in Australia, but South Africa and Greece. The smoke might have gone away and the vineyards might seem undamaged, but the flavour might still appear in the wine. It’s not very nice: you’d probably write notes like “ashtray” or “acrid”. And unlike eucalyptol, it appears in white wines as well as red. How noticeable it is depends on the weight and structure of the wine: the threshold for detection on the palate is much, much higher in, say, full-bodied Shiraz than in light, sparkling white.

That it is noticeable in white wines at all suggests that it gets into the pulp rather than sitting on the skins; indeed, there have been tests that involve washing grapes with high-pressure hoses after a fire, and while the water gets off the ash and dirt it doesn’t affect the concentration of smoke taint in the finished wine. Smoke taint seems to come largely, but not entirely, from substances called guaiacol and 4-methylguaiacol, and levels of these can build up in the grapes even after the fire is long over, suggesting that they enter the plant via the leaves and are then fed into the grapes as they ripen. This makes smoke taint a difficult nut to crack. Fining doesn’t seem to shift it; reverse osmosis might have some effect, but not necessarily enough. It also seems to be composed of several substances, not all of which have yet been identified.

This makes it even more curious that in Italy’s Chianti Rufina, as reported by decanter.com, the local consorzio is not opposing plans to build a vast incinerator near the vineyards. Is a local incinerator part of a region’s sense of place? Just when winemakers thought they were learning how to master terroir…

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