Wine Chemistry and Biochemistry

10 Aromatic Spoilage of Wines by Raw Materials and Enological Products 609

Table 10.1Example of contaminated corks (ng/g)

TCAa TCP TeCA TeCP PCA PCP

Cork no. 1 543 319 8 3 48 5

Cork no. 2 1190 1146 3 5 13 6

aTCA, 2,4,6-trichloroanisol; TeCA, 2,3,4,6-tetrachloroanisol; PCA, pen-

tachloroanisol; TCP, 2,4,6-trichlorophenol; TeCP, 2,3,4,6-tetrachlorophenol;

PCP, pentachlorophenol

Table 10.2Examples of corks contaminated by the breakdown of wood treatment products
(ng/g of cork)

TCAa TCP TeCA TeCP PCA PCP

Cork no. 1 1 0 379 8 4350 17

Cork no. 2 3 0. 3460. 3 160 16

aTCA, 2,4,6-trichloroanisol; TeCA, 2,3,4,6-tetrachloroanisol; PCA, pen-

tachloroanisol; TCP, 2,4,6-trichlorophenol; TeCP, 2,3,4,6-tetrachlorofenol; PCP,

pentachlorophenol

strongly contaminated by cork TCA, all the bottles stopped with corks from the

same batch are also contaminated to some degree.

On the other hand, there are also corks that are simply contaminated by storage in

an atmosphere contaminated by the breakdown products of the polychlorophenols

used to treat the pinewood of the palettes or shelving where the bottles are stored

(Bertrand and Barrios 1994). This contamination is easy to detect because TCA is
always present at lower levels than TeCA and PCA (Table 10.2).

If the contamination has taken place after the bottles were corked during storage

on the palettes then the defect will be on the external part of the cork.

10.6.2 Origin of the 2,3,4,6-Tetrachloroanisol

Apart from the case reported above, this defect usually affects wine in the barrel.

The perception threshold for TeCA is around 15 ng/L for experts and 35 ng/L for

experienced consumers. The flavor defect is described as powdery, dry and musty.

Pentachlorophenol (PCP) and its sodium derivative (Na PCP) have been used

for some time to prevent the pinewood from taking on a bluish color. In addition,

it is an excellent pesticide and, also, seems to function as an insecticide. It often

contains 2,3,4,6-tetrachlorophenol as an impurity and, less frequently, 2,4,6-TCP.

At the surface of the wood, at a depth of 1 or 2 mm, the levels of PCP may exceed

1 mg/g (Table 10.3).

In the damp atmosphere of the wine cellars, moulds can break down PCP and

become detoxified as pentachloroanisol, which is volatile but has little aroma. In

contrast, tetrachloroanisol, even at very weak doses can contaminate the wine during

decanting or bottling (Table 10.4).