Abstract:
To investigate the physicochemical properties and key aroma compounds of Yihong congou tea across different seasons, a multidisciplinary methodology was employed, integrating sensory evaluation, colorimetry, standardized physicochemical assays, headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS), and gas chromatography-olfactometry (GC-O). Samples of spring-, summer-, and autumn-harvested teas from high-altitude regions were systematically analyzed. Results showed that significant seasonal differences were found in physicochemicals. Spring tea exhibited the highest amino acid content (4.13%,
P<0.05) and sensory evaluation scores, along with the highest volatile compound concentration (1633.68 μg/kg,
P<0.05). Summer tea had the more content of polyphenols (10.76%,
P<0.05), while autumn tea showed increased soluble sugar content (5.69%,
P<0.05). 63 volatile compounds were identified across seasons, including 40 common to all samples. Orthogonal partial least squares-discriminant analysis (OPLS-DA) and variable importance in projection (VIP) identified 7 key discriminators (VIP>1,
P<0.05): Nerol, linalool, methyl salicylate, (E)-2-hexenal, nonanal, linalool oxide I, and citral. GC-O analysis detected 18 aroma-active compounds. Phenylacetaldehyde, linalool oxide II, linalool, and
β-ionone demonstrated high aroma intensity (AI>2.5). A comparative analysis of the aroma components in Yihong Gongou tea across different seasons showed notable seasonal differences in phenethylaldehyde, a key element of floral sweetness. Higher aroma levels of linalool, linalool oxide II, and (E)-furanoid linalool oxide were found in spring tea. In summer tea, increased aroma activity was detected in fresh-scented compounds N-butyric acid (trans)-2-hexenyl ester and
α-phellandrene. The woody aroma compound
α-terpineol was only found in autumn tea. Integrated analysis of GC-O and relative odor activity value (ROAV) established linalool (ROAV>10, AI>3.0), nerol (ROAV>10, AI>2.5),
β-ionone (ROAV>1, AI>2.5) and nonanal (ROAV>1, AI>2.0) were the key aroma compounds. These findings could provide a theoretical foundation for enhancing the quality of Yihong Congou tea and the utilization of fresh leaf resources.