A GC-MS Based Analytical Method for Detection of Smoke Taint Associated Phenols in Smoke Affected Wines

Davinder Pal      Singh; Ayalsew      Zerihun; David      Kelly; Nicole   Marie   Cain; Peter      Nankervis; Mark   Oliver   Downey

Abstract

Guaiacol and 4-methylguaiacol are routinely used as markers to determine extent of smoke impact on winegrapes and wines. However, smoke contains a complex group of compounds that may contribute to smoke taint in winegrapes and wine. In this study, a gas chromatography-mass spectrometry (GC-MS) based analytical method was developed and validated for the profiling of various smoke taint compounds in wines made from smoke affected fruit. A total of 22 analytes were separated and identified in the GC-MS chromatogram, all of which were selected to evaluate the samples and precision of the method. The GC-MS method showed good repeatability/reproducibility with intra- and inter-day relative standard deviation (RSD) of ±14%. The method was used to demonstrate that the smoked grapes and resultant wines, compared to unsmoked wines, contained significantly enhanced levels of guaiacol and 4-methylguaiacol along with other lignin derived phenols such as cresols and syringol. In smoke affected grapes and young wines, volatile phenols exist as glyco-conjugates (potential taint), which hydrolyse slowly leading to unacceptable levels of taint accumulation in wine during storage. The GC-MS method reported here, in conjunction with the optimised acid hydrolysis of phenol glycoconjugates, was successfully used to determine potential levels of smoke taint compounds in wines. Thus, the method can be used for screening smoke exposed grapes for potential taint levels prior to wine making. The results presented here highlight the need to include an array of smoke derived phenols to develop a complete picture of smoke taint and associated aroma in affected grapes and wines.

Keywords: Acid hydrolysis, gas chromatography-mass spectrometry, glycosides of phenols, lignin, smoke taint, solid phase extraction, volatile phenols, wine.