Scientists in Bordeaux have discovered a new cause for corked flavours in wines which reveals that in many cases cork is not the culprit, research published last week shows.
Until now, a group of molecules known as chloroanisoles, including TCA and TeCA, were the only known culprits for the unpleasant, mouldy smell of corked wine. The new research reveals that TBA can also spoil wine in this way.
Previous research had revealed that in a large number of corked wines levels of TCA were insignificant. This prompted oenologist Pascal Chatonnet and a team at Excell Laboratory in Merignac, Bordeaux to search for another cause of contamination.
Using mass spectrometry and gas chromatography they discovered TBA (2,4,6-tribromoanisole), a molecule which behaves in a similar way to TCA. The research took several years but now TBA can be detected during winemaking, storage and bottle-ageing.
TBA causes wine to taste corked at concentrations as low as 4 nanograms per litre in still wine. Some tasters may notice it at even lower levels, as the odours often reveal themselves in the aftertaste.
Whilst conventional cork can release TCA into wine, it is not the only source of pollution. Biochemical breakdown of certain pesticides, over-zealous use of bleach in cleaning wineries, and atmospheric pollution can lead to TCA contamination.
TBA is also caused by elements present in the winery environment. As the research says, ‘Barrel wood, plastics, and corks are all highly susceptible to contamination by TBA from the air in production facilities.’ A widely-used flame retardant also produces TBA.
Old wooden structures could also release TBA, and, even after the original source of pollution has been removed, residues absorbed by walls could be enough to make the building unsuitable for storing wines.
The research is published in full in the Journal of Agricultural and Food Chemistry.
Written by Frances Robinson