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The 'burnt rubber' factor There's something there, but it's not (yet) affecting sales From Business Day, 11 June 2008
The allegations that surfaced recently about the “burnt rubber” aromas supposedly associated with Cape wine have now been substantially aired in the local press — and can no longer be called “the wine industry’s dark secret”. Jane MacQuitty — the UK writer who, more than anyone else, made a point of publishing what she didn’t like about Cape wines — may have done the South African wine industry a huge favour. While there is no certainty that what she disliked so intensely can actually be identified, she has forced producers and the generic export body to investigate the allegations pretty thoroughly. (In fairness to MacQuitty, she was equally scathing about Australian wine a few weeks after her article on SA appeared. No one can accuse her of selective virulence — a point worth noting in this xenophobic age.) Wines of SA — the body charged with marketing Cape wine abroad — has commissioned a study to determine the origin of this unseemly pong. It began by getting a panel of UK tasters to work its way through a range of South African reds. Where there was general consensus about the evidence of this unfortunate trait, the wines in question will undergo more detailed research. A team at the University of Stellenbosch now believe that at least they recognise what the UK writers dislike in these wines and are following up the tasting with microbiological and chemical analysis. Field investigations will follow later this month — the idea being to determine if the problem has its origin in vineyards, varieties or rootstocks. No one is saying if and when the villain will be unmasked. It is interesting that despite the many competitions, shows and panel tastings which take place in SA annually, this particular problem — the so-called “burnt rubber aroma” has never been mentioned domestically. This may be the result of what is called a “cellar palate” — when the taster is so accustomed to a certain feature that he ceases to notice it; it may be that what the UK calls “burnt rubber” is described in SA in an entirely different way. I work with a lot of overseas tasters and there are features in Cape wines (mainly, I have to say, in the less premium segment of the market), which we ascribe to the endemic problem of vineyard virus. The shorthand used to note this taint is either “sun-dried tomato” or “rhubarb” and close investigation of the vineyard and its virus status almost always provides the necessary corroboration. Perhaps what we call “rhubarb” is what the UK writers think is a note reminiscent of “burnt rubber”. Sam Harrop, the UK judge who was in SA recently, hazarded a guess that the origin of the taint could be a sulphur compound. This makes sense in that smoky, eggy notes are associated with sulphur that has been free to evolve in a relatively oxygen-free environment. Yet if this is the case, it is strange that it hasn’t been noted before to any extent at South African tastings. Reduction due to lack of air is a well-known and easily identified fault. That said, the problems with Brettanomyces (or “brett” in everyday parlance) — the spoilage yeast which imparts an “Elastoplast” or horse-blanket smell to mainly red wines — were only widely recognised in the past five years. And just as the presence of brett is quite widespread, it has had little effect on South African wine exports — which have grown (with one exception) year on year at a rate exceeding 10% compounded. Perhaps the burnt rubber problem occurs in a small percentage of high-profile wines — the collectables which land up at tastings attended by influential UK hacks. Perhaps the average wine buyer doesn’t notice, or doesn’t care. However, with exports to Britain up 17% from January to April — and globally up 35% for the first quarter this year — the problem may have reputational implications. But it’s not (yet) affecting sales.
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COMMENTS
From Peter May:
From Hans Moser (of The Governor Tulbagh Wine Estate) If it is assumed, that the "burnt rubber aroma" could be the same as the "sun-dried tomato" or "rhubarb" aromas and linked to the virus status of the vineyards, why does it not show up in other wine producing countries? That virus is not exclusive to SA and is found unfortunately in almost all vineyards around the world. The aroma development is depending on the berry temperature. We know that most of the desirable aromas are developed in the last 8 weeks before harvest at a temperature range between 12 and 18 degrees Celcius. It would be very useful to establish the temperature range of the berries producing that flawed wine have been subjected to. Could it be that the ripening temperature was too high? When we started out to find a suitable "terroir" we appointed the viticulturist Maxime Debure of ENSA-Montpellier to do a study on the suitability of various grape growing region in SA and compared it the international well known regions. We then used as benchmark the temperature range of the last 8 weeks to harvest of good vintages in Bordeaux. We then compared it to various grape growing regions in SA and internationally. Here as example Stellenbosch (Nietvoorbij), Tulbagh Valley (Drosty - 160m) and our property in Tulbagh at 500m. The average minimum temperature of SA growing regions were acceptable in comparision to Bordeaux
The average temperature was less desirable (8 weeks to harvest)
However the maximum temperature was far out of the desirable range
We found that Tulbagh Valley is typical for the bulk of grape growing regions. Temperatures in Paarl, Wellington, Worster are very similar to the measured temperature range of Tulbagh Valley. We know that berries start disintegrating their flavours if heated up to more then 35 degrees. Berries get warmer by more then 10 degrees then ambient temperature if sun exposed, and even shaded berries are warmer by a few degrees then the ambient temperature. It is thought, that the high temperature starts a chemical process of flavour desecretion and through that off-flavours are developed. Could it be that the "burnt rubber" flavour is linked to the high temperatures? The maximum temperature samples of the other well known wine growing region around the world showed far less exposure to extreme temperatures during ripening. High maximum temperatures during ripening - we harvest far sooner then in most other regions and are more exposed to the high mid-summer temperatures - are a given in the Cape. In order to improve the overall quality we need to shift the growing of wine grapes closer to the sea and to higher altitutes. Even at 500 m in Tulbagh we still are exposed to extreme heat-waves during ripening. At The Governor Tulbagh we are addressing that problem by installing evaporating water cooling. We have been assured that we can reduce the berry temperature to below 10 degree of ambient temperature by using that system. It is expensive, but we made the decision to produce quality wine. In future, as global warming will make many of the already marginal SA growing regions even more unsuitable, it will be in the interest of the wine industry to concentrate only on regions with suitable temperatures.
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From Vieilles Vignes: Some very interesting points backed with some impressive data. The combination of heat with other compounds might be a possibility, problem in this lies that such a hypothesis will be proved wrong in five minutes, because not all wines with McQuitty Syndrome come from heat affected vineyards, likewise not all heat affected vineyards manifest these aromas, and the affected wines are not restricted to Bordeaux varieties. And we are not the warmest wine producing area by any stretch of the imagination: Priorat, Rioja, sections of Rhone, Australia... There's definite merit in pursuing this as possibility, but more likely it would act as a catalyst for a reaction rather than a action upon itself. |
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Response from Hans Moser Maxime investigated the heat accumulation and harvesting temperatures of Rioja, Rhone Valley and various other wine producing regions. The interior of Spain has a very cold winter and through that a relative short growing season. Also the hottest month is July, long before harvest. At harvest the temperature have again dropped substantially. This also applies to a lesser degree to Australia. I use some of the data complied by Maxime as an example. Heat summation for growing season (above 10 degrees):
Average maximum temperature in the month of harvest:
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