Submitted to: Southern Region of the American Society for Horticultural Science
Publication Type: Abstract only
Publication Acceptance Date: 2/11/2010
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Shrubs of clonal selections of Thymus hyemalis L. and Spanish T. vulgaris subsp. vulgaris were harvested at five phenological stages during the plant growing cycle: vegetative (VEG), floral (FL), floral-fructification (FL-FR), fructification (FR), and passed fructification (FR-pas). The volatile profile of the essential oil samples was determined by capillary gas chromatography coupled with an olfactometry detector (GC-O) and two trained panelists evaluating samples in triplicate runs. Sample aromatic profiles were also evaluated by a 10-member panel using the free-choice profiling (FCP) method in which panelists are allowed to use their own vocabulary. Peak intensities obtained by GC-O were analyzed using ANOVA and by principal components analysis (PCA). Sensory data were analyzed by the general Procrustes analysis (GPA). T. hyemalis and T. vulgaris had 36 and 28 aroma-active compounds, respectively, perceived in a consensus by the two GC-O panelists. For T. hyemalis, the VEG stage was characterized by high green/menthol peak intensity due to a-terpinene. The FL stage also had high intensity for green/menthol ('-terpinene), raspberry (ß-ionone), as well as unknown peak with fresh/herbal aroma. One unknown compound with spice/anise aroma was perceived in FL-FR and absent in other stages. The FR and FR-pas stages had high intensity for many peaks, including a-myrcene (engine oil), bornyl acetate (herbal/menthol) and spicy (eugenol). The FCP analysis revealed that the FL stage was well differentiated from other stages, with a dominant of medicinal, cedar, earthy/musty aromas. The FR-pass stage was also distinct from FL by honey and engine oil notes. T. vulgaris differed from T. hyemalis by the presence of terpenyl acetate (spice/herbal) and the absence of p-cymene (engine oil), bornyl acetate (woody) and thymol/carvacrol (herbal/thyme). Eucalyptol (menthol) and eugenol (spice/clove) were also higher in T. vulgaris. As a result, the essential oil of T. hyemalis was perceived with more negative notes (engine oil, earthy/musty, pencil) than T. vulgaris, which had floral, herbal, spices, and menthol descriptors.