Cork taint is a common problem in wine production, resulting in an unpleasant musty or mouldy odour in the wine. This problem is caused by the presence of certain chemical compounds, including chloroanisoles and bromoanisoles.
Chloroanisoles, specifically 2,4,6-trichloroanisole (TCA), 2,3,4,6-tetrachloroanisole (TeCA), and pentachloroanisole (PCA), are the main culprits in mouldy and clogged wines. The presence of TCA in bottled wine comes generally from contamination by the cork stopper itself, which contains TCA.
However, the TCA present in wine in vats comes either from the use of chlorinated hygiene products (such as bleach) or from the use of humidifiers operating with highly chlorinated mains water. Chlorine reacts quickly on contact with phenols in wood, wine residues, or even certain floor coverings made of polymer resins to form trichlorophenols (TCP). The mould present in the cellar then transforms the TCP into a very volatile TCA. Then, through air movement, contamination can spread throughout the cellar. In addition, if traces of chlorine are found in the wine, following insufficient rinsing, TCP is formed on contact with the phenols in the wine, followed by TCA by the microorganisms present in the wine or during contact with the cork.
In addition, many insecticide treatment products and wood fungicides (framework, pallets, doors, etc.) contain tetra- and pentachlorophenols (TeCP and PCP).
Moulds present in the cellar can transform them into chloroanisoles, tetra-, and pentachloroanisoles (TeCA and PCA), which are malodorous, and very volatile. The presence of these last two molecules in the wine is a sign of airborne contamination. This mode of alteration concerns much larger volumes than the TCA problems in bottles.
Other molecules responsible for musty tastes in wines have recently been highlighted. These are bromoanisoles, and in particular 2,4,6-tribromoanisole (TBA). They develop through the action of moulds on particular precursors, most frequently bromophenols. The contamination would be diffused by the atmosphere of the cellar from the treated wood. It could also come from metal plugging caps (varnish made from brominated epoxy resins), from wood chips themselves that are contaminated, or from airborne contamination from fireproof insulation containing tetrabromobisphenol-A-based flame retardants.
To eliminate these compounds from wine, it is important to identify the source of contamination and take appropriate measures. For example, winemakers can use alternative closures to cork stoppers, such as synthetic corks or screw caps, or ask their cork suppliers for certain specifications. More and more, cork suppliers use specific treatments (washing or supercritical CO2) to remove anisoles from their products, minimising the risk of contamination coming from the closure.
In addition, they can avoid the use of chlorine-based cleaning products in the winery and steam clean or use gas chromatography to remove these compounds from cork stoppers or other surfaces.
There are various methods, depending on wine country regulations, to treat the affected wine, like activated carbon, which absorbs the compounds responsible for cork taint; using ozone or hydrogen peroxide gas to treat the wine in combination with reverse osmosis membrane filtration, which can oxidise. It’s important to note that these methods may affect the wine’s taste and aroma, so it’s important to carefully evaluate the wine after treatment.
Another way is to use specific yeast cell walls with high absorption capacity.
We tested Extraferm D’tox in a large tank of red wine and found high levels of TeCA and PCA of 60 and 147 ng/L, respectively. A 48-hour contact between the cell walls and the wine to be treated, combined with agitation by pumping 2-3 times a day, enabled the success of the decontamination treatment. The tasting gave complete satisfaction in terms of the elimination of the musty character compared to the control wine, as well as the absence of a yeast taste. The high-volume processing took place in the cellar at 40 g/hL. The analyses then carried out showed a reduction of TeCA and PCA of, respectively, 60 and 61%. We were able to show the effectiveness of the treatment in reducing the levels of TBA, a molecule whose threshold of perception is as low as that of TCA and which gives the wine the same defect. We got a significant reduction of 78%. These large-volume tests confirmed the effectiveness of Extraferm D’tox yeast cell wall treatment for the decontamination of wines containing haloanisoles.
With a highly qualified team of experts in many fields, Oenobrands strives to offer winemakers’ novel and scientifically sound solutions, as well as to highlight the positive synergies between its products.
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