Absorption of chloroanisoles from wine by corks and by other materials

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Abstract
Sixty 750 mL bottles of a white wine were each spiked with deuterium-labelled 2,4,6-trichloroanisole (d5 TCA) and then sealed with a variety of wine corks. Thirty months later, approximately half of the d5-TCA had been absorbed by each of the corks, regardless of supplier, bleaching treatment or whether the corks were natural or agglomerate. In addition to the added labelled TCA, every one of these corks also contained endogenous (i.e. unlabelled) TCA. Fifteen of the corks, mostly agglomerates, imparted some of their endogenous TCA into the wines. There was no direct relationship between the amount of endogenous TCA in the corks and that found in wines. The high variability in the distribution of endogenous TCA between wine and cork contrasts with the relatively uniform distribution of the d5--TCA. This contrasting behaviour distinguishes between wines tainted prior to closure and wine tainted by corks. Natural bark corks in wine bottles can also absorb 2,3,4,6-tetrachloroanisole (TeCA) and pentachloro-anisole (PCA) from bottled wine. Bottle storage of commercial wines that had become tainted with TeCA and PCA during production resulted in the corks absorbing most of these two compounds, so that the wines were no longer tainted to a significant extent. Soaking whole corks in wine spiked with chloroanisoles, under conditions typically employed in the wine industry to test batches of corks for possible taint, resulted in most of the TCA in the wine being absorbed by the corks. Thus, if five corks are being soaked in wine in order to test for taint, four sound corks could reabsorb TCA that had leached into the surrounding wine from a single contaminated cork, reducing the concentration of TCA to a point where it escapes detection. Soaking corks singly rather than in groups of five will therefore be a more sensitive method of screening batches of corks for taint than soaking them in groups of five. Plastic materials such as the lids of glass containers used to store wine samples were also able to absorb chloroanisoles via both direct liquid contact and the vapour phase. Wine cask bladders and polyethylene film were particularly effective in removing TCA from wine.