The characterization of volatile floral scent in Phalaenopsis-type Dendrobium hybrids

Phalaenopsis-type Dendrobium hybrids (den-phals) are globally important ornamental plants. Aromatic commercial den-phals are rare, but the fragrance of their flowers has gradually become a significant trait influencing consumer preferences. In this study, 22 aromatic den-phals were screened by sensory evaluation. Then headspace solid–phase microextraction and gas chromatography-mass spectrometry (GC–MS) were employed to investigate the aroma profiles of nine out of the 22 aromatic den-phals at different flowering stages, times of the day, and floral organs. The results showed that the 22 den-phals could be categorized into three groups, based on different aroma intensities: light fragrance (five hybrids), medium fragrance (nine hybrids), and strong fragrance (eight hybrids). A total of 137 volatile compounds were detected in all samples according to the GC–MS results. Both the quantity and variety of volatile compounds exhibit an initial increase followed by a decrease during different flowering stages and times of day. Full flowering stage reached its peak, with its highest content at 12:00, with the highest types at 16:00. Petals have the highest variety of volatile compounds, while sepals have the highest content. The odor activity values indicated that linalool, hexanal, (E)-2-hexenal, (E)-2-octenal, (E,Z)-2,6-nonadienal, (E)-2-nonenal, octanal, nonanal, 2-pentyl furan, decanal, and β-ocimene contributed significantly to the aroma of den-phals. The grassy aroma of den-phals was primarily contributed by hexanal and (E)-2-hexenal, and the floral aroma was characterized by linalool, β-ocimene, and trans-β-ocimene. Octanal and nonanal were the main aroma compounds associated with a fruity aroma, while caryophyllene contributed to a spicy aroma.