Simultaneous assay of Chlorophenols and Chloroanisoles in wines and corks or cork-based stoppers. Application in determining the origin of pollution in bottled wines

Abstract

<p style="text-align: justify;">The contamination of wines and, more rarely, of brandies by corks or cork-based stoppers used as bottles closures has been a recurring issue for many years. The relative frequency of this type of spoilage, characterized by the distinctive, unpleasant odor of «moldy cork taint», has led to a considerable body of research on this subject. In wine, 2,4,6-trichloroanisole (TCA), produced by the methylation of its direct precursor, 2,4,6-trichlorophenol (TCP), has clearly been identified as the main compound responsible for the "moldy off-flavors" produced by defective corks. In this study, we present a method for assaying the main chloroanisoles and chlorophenols identified as potential contaminants in wines and corks or cork-based stoppers (2,4,6-trichloroanisole and -phenol, 2,3,4,6- tetrachloroansiole and -phenol, pentachloroanisole and -phenol). An extraction method using dichloromethane for cork and a dichloromethane/-pentane mixture for wine isolates almost the entire quantity of organochlorine contaminants from these matrices. The chloroanisoles and precursors are identified simultaneously by gas-phase chromatography coupled with electron impact mass spectrometry with selective ion monitoring. This method provides an accurate analysis of the contamination with a view to establishing the type and origin of the "musty, moldy, corky" characteristics in bottled wines by studying the migration of contaminants from the stoppers into the contents of the bottles. This method for the simultaneous assay of chlorophenols and chloroanisoles was defined in compliance with the following standards: NF ISO 5725-1/2, NF V 03110 (AFNOR), and MA-F-AS1-06-PROVAL (OIV). The method is specific, accurate, linear, repeatable, and has been validated. The detection and quantification ranges are compatible with the sensitivity requirements for this type of contaminant.</p>