Comprehensive two-dimensional gas chromatography-high resolution mass spectrometry for the detailed qualitative analysis of old vine Chenin blanc wine volatiles and comparison with young vine Chenin blanc wines

Old vine Chenin blanc (OVC) wines are produced from grapes harvested from vines older than 35 years, verified as Certified Heritage Vineyards in South Africa. This emerging premium wine style is of interest due to the purported unique sensory properties of these wines, including their complex aroma. There is however limited information available on the volatile constituents of these wines, which are primarily responsible for perceived aroma. The wine volatilome is exceedingly complex, and requires advanced analytical approaches to investigate. The present contribution reports the evaluation of comprehensive two-dimensional gas chromatography (GC × GC) as a powerful separation technique to gain qualitative insight into the volatile composition of OVC wines. Extraction of volatile compounds was performed using headspace solid-phase microextraction (HS-SPME), while the GC × GC separation was hyphenated to high speed high resolution time-of-flight MS (HR-TOF-MS) for compound identification. A representative set of eight Chenin blanc wines produced from young vines (YVC) was also analysed to investigate the potential use of GC × GC-HR-MS data to differentiate these two wine styles based on differences in their volatile composition. The results confirm the utility of GC × GC-HR-MS for the detailed qualitative analysis of wine volatiles, with a total of 277 compounds identified in the studied wines. 53 compounds were uniquely identified in the OVC samples, and 52 in YVC wines. Successful differentiation of the young- and old-vine wines was achieved based on tile-based Fisher (F) ratios and principal component analysis (PCA), although this differentiation could not be clearly linked to winemaking practices (wood maturation) or viticultural origin.