Analysis of honeybush tea (Cyclopia spp.) volatiles by comprehensive two-dimensional gas chromatography using a single-stage thermal modulator.
2017
Ntlhokwe, Gaalebalwe | Tredoux, Andreas G. J. | Górecki, Tadeusz | Edwards, Matthew | Vestner, Jochen | Muller, Magdalena | Erasmus, Lené | Joubert, Elizabeth | Christel Cronje, J. | de Villiers, André | Department of Chemistry and Polymer Science ; Stellenbosch University | Department of Chemistry ; RIDER UNIVERSITY | Center of Analytical Chemistry & Microbiology, Department of Microbiology and Biochemistry ; Hochschule Geisenheim University | Unité de Recherche Oenologie [Villenave d'Ornon] (OENO) ; Institut National de la Recherche Agronomique (INRA)-Université de Bordeaux (UB)-Institut des Sciences de la Vigne et du Vin (ISVV) | Université de Bordeaux (UB) | Institut des Sciences de la Vigne et du Vin | Department of Food Science ; Cornelle University | Post-Harvest and Wine Technology Division ; Agricultural Research Council [Pretoria, South Africa] (ARC) | Department of Forest and Wood Science ; Stellenbosch University
The applicability of comprehensive two-dimensional gas chromatography (GC×GC) using a single-stage thermal modulator was explored for the analysis of honeybush tea (Cyclopia spp.) volatile compounds. Headspace solid phase micro-extraction (HS-SPME) was used in combination with GC×GC separation on a non-polar × polar column set with flame ionisation (FID) detection for the analysis of fermented Cyclopia maculata, Cyclopia subternata and Cyclopia genistoides tea infusions of a single harvest season. Method optimisation entailed evaluation of the effects of several experimental parameters on the performance of the modulator, the choice of columns in both dimensions, as well as the HS-SPME extraction fibre. Eighty-four volatile compounds were identified by co-injection of reference standards. Principal component analysis (PCA) showed clear differentiation between the species based on their volatile profiles. Due to the highly reproducible separations obtained using the single-stage thermal modulator, multivariate data analysis was simplified. The results demonstrate both the complexity of honeybush volatile profiles and the potential of GC×GC separation in combination with suitable data analysis techniques for the investigation of the relationship between sensory properties and volatile composition of these products. The developed method therefore offers a fast and inexpensive methodology for the profiling of honeybush tea volatiles. Graphical abstract Surface plot obtained for the GC×GC-FID analysis of honeybush tea volatiles.
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