Understanding that ‘burnt rubber’ aroma 3 June 2008

Analytical process underway to find source of problematical flavours in some Cape reds

By Tim James

For a year or two there have been increasingly vociferous reports, particularly but not only from England, about an offensive character in many South African reds: words like rubber, burnt, singed, smoky being commonly used in disparagement. There has been little resonance within South Africa, partly because it would seem that those who are particularly accustomed to drinking local reds had acquired some sort of ‘cellar palate’, which tended to screen the specific problem. There has been comment, however, by some local critics that Cape whites are on the whole better than Cape reds, as well as increasing awareness of problems associated with stressed vines, virus-ridden vines and the combination of 'greenness' with 'ultra-ripeness'.  

The difficulty for local writers in getting to grips with the perspective of the foreign critics on this particular issue was not helped by the fact that the outsiders never made public comments in relation to specific wines, unfortunately confining themselves to negative generalisations.

In terms of public perception and media comment, this strain of criticism came to a head in April this year, when a British winewriter, Jane McQuitty, wrote in particularly insulting, dismissive and extreme – but still unspecific – terms about the problem in The Times of London. (It should be said that for many people, including the present writer, it was not the judgement itself that was the problem, but the tone and the generalising irresponsibility evidenced in conveying it. Jancis Robinson – a critic with a somewhat more elevated reputation than Ms McQuitty appears to have amongst her peers, incidentally – was prompted to a rare public disagreement with a fellow winewriter and wrote, in the Members' Forum section of her website, of McQuitty’s piece as ‘a potentially damaging and ill-informed blanket attack’.)

Wosa action

Given the long and persistent trend of the negative criticism, it has for some time been clear to Wosa, the body responsible for generic marketing of South African wine, that something serious needed to be done. As a first step, to isolate a selection of ‘guilty’ wines, Wosa decided earlier this year to enlist the help of a group of eminent tasters in London (some of whom waived the fee, all of whom were generous in participating). When a date suitable to all could finally be set, a blind tasting was held, and although there was not always unanimity in identifying the ofensive 'burnt' character, there was sufficient agreement to produce two lists: one of affected wines and one of 'clean' wines. Although there is no public awareness of these lists' contents, it would seem that both the 'clean' and the 'dirty' lists include both cheap and expensive wines.

A team of scientists at the University of Stellenbosch had already been assembled, and was only waiting for the lists in order to move forward. Their task would be to precisely define the problematic aroma/flavour, then to establish what it in fact consists of, and what is causing it. Later there will hopefully be the chance to inform producers of ways to overcome the problem, on a scientifically solid basis.

In a recent statement, Wosa says that

The University was supplied with two sets of wines – the suspects and the clean control samples.  Several rounds of tastings have been concluded in South Africa and the research team is confident that they have a grasp of the aroma in question and a solid line-up of wines to work with.

Microbiological and chemical analysis, including HPLC, GC-FID, GC-MS and infrared spectroscopy is already in progress to establish whether specific microbiological or chemical profiles can be linked to the character. Investigations in the field will commence in June.  Each wine, whether problematic or not, will be researched and traced back, literally to its roots, to identify common denominators which can lead the research project to a conclusive result.  Parallel to this phase, a gas-chromatography-olfactory analysis (GC-O) will also commence, with the objective to identify specific chemical compounds that are responsible for this character.

It is obviously difficult to say at this stage how long the analytical project might take, given the uncertainty of the nature of the problem – it might be that the cause is particularly complex, or even due to more than one factor.

As an adjunct to the research project, there are also plans to help the local wine industry (winewriters, judges, etc) come to a better understanding of what their international colleagues have noticed.