The Australian Wine Research Institute’s Analytical Service - Analyses

TCA Analysis

Chloroanisoles have been shown to be capable of imparting a musty taint to a variety of foods and beverages, including wine. The most potent of the chloroanisoles is 2,4,6-trichloroanisole (TCA). The aroma detection threshold of TCA in wine has been determined as ranging from 1.4 ng/L to 4 ng/L depending on wine type, while 2,3,4,6-tetrachloroanisole (TeCA) has a somewhat higher aroma detection threshold than TCA (reported as 14 ng/L in a Pinot Noir wine). These two compounds are responsible for most incidences of musty taint in wines encountered by the Institute.

Recently, 2,4,6-tribromoanisole (TBA) has been reported in wine with an aroma threshold similar to that of TCA.

The most common causes of musty taint in wine are generally the cork closure or contaminated oak products. In virtually every case of cork taint investigated, TCA has been shown to be the compound responsible for the musty odour. When musty taint in wines has been derived from contaminated oak products (both barrels and chips), both TCA and TeCA, sometimes in combination, have been shown to be responsible for the taint.

How does the analysis work?

A new method for the analysis of chloro- and bromoanisoles in wine, cork and oakwood has been developed by the AWRI. The analytical technique, known as headspace-solid phase microextraction (HS-SPME), uses a specially coated fibre to adsorb the analytes from the headspace above the sample. The fibre then releases these compounds into the heated injector block of a GC/MS. The method shows good accuracy, as it utilises deuterated-TCA as an internal standard, and allows for detection of the analytes at a very low concentration as only the volatile compounds are being sampled from the headspace. Corks are completely submerged for 24 hours in a model wine solution while oak products are soaked in the same model wine solution for 7 days. In both cases, the model wine extract is then analysed as a normal wine. The method provides analysis of the following compounds: 2,6- and 2,4-dichloroanisole, 2,4,6-trichloroanisole, 2,4,6-tribromoanisole, 2,3,4,6-tetrachloroanisole and pentachloroanisole.

How can this analysis assist winemakers?

Where musty taint in wine is encountered, analysis of wines (and corks where relevant) will determine whether chloroanisoles are responsible for the taint. This allows industry to seek appropriate redress, where materials supplied to a winery are responsible for the taint. In addition, screening of oak chips/shavings prior to use will reduce the risk of wines becoming contaminated with chloroanisoles as a result of the use of these products.

How do I submit samples?

Recent research by the Institute has shown that plastic components of packaging material (i.e. lids of jars) can absorb a high proportion of chloroanisoles from wine samples. It is, therefore, important that samples sent for analysis be correctly packaged.

Samples should be submitted in glass jars (a 100 mL jam jar is perfect) with double layered aluminium foil between the jar and lid. This is to prevent the absorption of the taint into the plastic insert of the lid. Before using a particular jar, check that when screwing down the lid that the foil doesn’t tear (this happens with Schott bottles). Cork and oak shavings or chips should be double wrapped in aluminium foil.

Where analysis of both corks and wines is required in cases of suspected cork taint, the wine and cork should be sent separately. If a bottle has been opened, the cork should not be reinserted in the bottle.