Veld fires occur all over the world and wine countries have to face this phenomenon which will not only have a direct physical impact on the vines but the secondary influences on the wine made from grapes exposed to the smoke resulting from the fires are unpredictable.

Contrary to the negative perception concerning the smoke taint of wines the smoking of different foods is a very sophisticated profession and the most information concerning smoking as a scientific topic is in this regard.

Many studies have been reported on the composition of wood smoke but the individual components responsible for the specific flavour of smoked products are still unknown. Although it was initially claimed that mainly phenols are of primary importance in the characterization of smoke flavour another report indicated that the three phenols rated as smoky by a tasting panel do not reproduce the character precisely. The unique smoky flavour is apparently not limited to one class of compounds but it seems that phenols and carbonyl compounds are the most important (Fiddler et al, 1970).

The acceptability of smoked foods is increasing not only as a preservative but as flavourant. The odour, composition and anti-microbial activity of wood smoke is highly dependent on the wood type. Some studies identified beech and oak as producing smoke with the best sensory properties but in Spain the use of vine shoots for the grilling of lamb and sardines is highly appreciated. Aqueous smoke preparations of vine shoots were compared with other woods. In the smoke of both woods the carbonyl derivatives were in higher concentrations than the phenol derivatives. Carbonyl derivatives like esters, aldehydes, ketones, diketones, furan and pyran derivatives are formed as result of the thermal degradation of cellulose and hemicellulose. These compounds are usually associated with caramel or burnt sugar aromas. Phenol derivatives are formed from the thermal degradation of lignin. The composition of the wood will thus determine the composition of the smoke provided that the influences generating the smoke are constant. It seems that ratios between concentrations of the main components can be used as parameters for the smoke characteristics (Guillen and Ibargoita, 1996).

It is however interesting to note that some of the compounds identified in the smoke of Vitis vinifera are similar to those which are related to specific flavours known in wine like the following:

  • Common esters which are associated with a fruity character.
  • Ethylphenol which is associated with Brettanomyces spoilage.
  • Ethylguaiacol which is associated with Brettanomyces spoilage.
  • Vanillin which is associated with wood maturation.
  • The smoke taint in wines can apparently be attributed to a wide variety of flavour compounds and the combination of the latter is mainly determined by the composition or origin of the wood. With the diversity of natural vegetation in the South African wine regions it will be a very complicated subject to research.

References:

1. Fiddler, W., Wasserman, A.E., Doerr, R.C. 1970. A Smoke Flavor Fraction of a Liquid Smoke Solution. J. Agr. Food Chem. 8(5): 934 – 936.
2. Guillen, M.D., Ibargoitia, M.L. 1996. Volatile Components of Aqueous Liquid Smokes from Vitis vinifera L Shoots and Fagus sylvatica L Wood. J. Sci Food Agric 72: 104 – 110.

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