One of the main factors constraining the growth of the tea business is the low use rate of summer tea. To enhance the utilization rate and improve the quality of summer tea, this study innovatively integrated shaking, freezing, and rolling into the traditional processing methods of white tea. Processing parameters were optimized through single-factor experiments combined with an L₉(3⁴) orthogonal experimental design. The quality of summer teas was systematically evaluated using sensory analysis, gas chromatography–mass spectrometry, and high-performance liquid chromatography. This study found that the optimal processing for summer tea was as follows: fresh leaves, room-temperature cold-air withering for 6.5 h, shaking at 10 rpm for 10 min, −20 °C freezing for 5 h, 25% strength rolling for 9 min, and drying at 75 °C for 2 h. The relative content of esterified catechins in summer tea produced by the optimal processing method was reduced by 14.62% compared with the control group. There were alterations in the content of amino acid components, with fresh and sweet amino acids increasing by 4.96% and 2.95%, respectively, and bitter amino acids reducing by 2.15%. Furthermore, γ-aminobutyric acid and L-theanine contents increased by 0.51% and 5.77%, respectively. Five characteristic volatile compounds were identified, namely, methyl salicylate, phenethyl formate, linalool, dimethyl sulfide, and isobutyraldehyde. The volatile profile was dominated by floral and fruity notes, except for dimethyl sulfide, which exhibited a distinct cooked corn-like aroma characteristic. This process was shown to improve the quality of summer tea. The results of this study provide a metabolite-level grounds for improving the quality of summer tea.

Oolong tea presents notable variations in taste profile and aroma characteristics under different cultivation conditions, particularly across altitudes. However, systematic investigations into the altitude-induced differences in key taste compounds and aroma composition remain limited. In this study, we examined six oolong tea cultivars, comparing their taste-related chemical constituents and aroma profiles under high- and low-altitude cultivation. Sensory evaluation, high-performance liquid chromatography (HPLC) and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) were employed to characterize these differences. Sensory evaluation revealed that high-altitude oolong teas exhibited enhanced umami, sweetness, and floral intensity. In most cultivars, the levels of free amino acids, polyphenols, and soluble sugar were relatively higher under high-altitude conditions. HS-SPME-GC-MS identified 55 common volatile organic compounds (VOCs), with terpenes and esters comprising the largest number of compounds. Identification by partial least squares discriminant analysis (PLS-DA) combined with relative odor activity value (rOAV) screening yielded 22 candidate differential volatile organic compounds. Floral monoterpenes, including linalool, linalool oxide II and geraniol, were consistently higher in high-altitude teas, whereas most other volatiles varied primarily with cultivar rather than altitude. These chemical patterns are consistent with the sensory finding of stronger floral intensity in high-altitude samples. This study provides theoretical insights for cultivar selection and quality improvement of oolong tea grown in high-altitude regions.

High-altitude environments provide a favorable basis for tea quality formation, but suitable processing parameters for high-altitude Oolong Tea (HAOT, Camellia sinensis (L.) O. Kuntze) remain unclear. This study optimized key processing parameters for HAOT using a three-factor, three-level orthogonal design involving withering method, shaking intensity and standing time. Sensory evaluation, quantitative descriptive analysis (QDA), macro-compositions determination, headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry (HS-SPME-GC-MS), multivariate statistics and correlation analysis were used to clarify quality differences and their chemical basis. Leaf anatomical observation showed that high-altitude fresh leaves had a thicker cuticle and more compact mesophyll structure, suggesting the need for targeted processing regulation. Range analysis indicated that shaking intensity had the largest R value for sensory scores, followed by withering method, whereas standing time showed a comparatively small R value. The favorable combination was combined withering, heavy shaking (6 rounds) and 60 min standing, hereafter referred to as FHM. FHM showed the highest floral and fruity aroma scores and produced a mellow, full-bodied taste with a sweet aftertaste. It also contained significantly higher flavonoid and soluble sugar levels than the other processing combinations. A total of 65 volatile organic compounds were detected, with terpenoids and esters as the dominant classes. ROAV analysis identified geraniol, linalool, β-ionone, (E)-nerolidol and benzaldehyde as representative major aroma-active compounds, while geraniol and linalool were especially prominent in FHM. Correlation analysis further linked flavonoids and soluble sugars with positive taste attributes, and linalool and geraniol with floral–fruity aroma. These results provide a practical basis for optimizing HAOT processing and improving product quality.

Oolong tea is prized for its floral aroma and bioactive tea polysaccharides (TPS), yet the independent contribution of cultivar genetic background to aroma chemistry and TPS functionality remains unclear due to confounding effects from environment and processing. Here, we systematically compared volatile organic compound (VOC) profiles and in vitro antioxidant activities of TPS from six Anxi oolong tea cultivars all grown in the same tea garden and processed under identical Qingxiang oolong tea protocols. Using headspace solid-phase microextraction-gas chromatography-mass spectrometry, 39 VOCs were identified across cultivars. Huangjingui exhibited the highest total VOC content (69.01 μg·g⁻¹) and the greatest number of compounds with relative odor activity values (rOAV) over 1. Principal component analysis and hierarchical clustering revealed clear metabolic separation among cultivars, with Daye Wulong displaying the most distinct metabolome. PLS-DA combined with rOAV screening identified 12 key differential volatiles that form the chemical basis of floral aroma. Preliminary in silico molecular docking predicted the strongest binding affinity between nerolidol and OR1A1 (−7.54 kcal/mol). Cultivar-specific high rOAV volatiles were characterized, including (E)-2-octenal and 1-phenyl-2-nitroethane in Tieguanyin, 2-phenylethyl-2-methylbutyrate and cis-3-hexenyl isovalerate in Maoxie, α-ocimene and cis-3-hexenyl benzoate in Daye Wulong, and (E,E,Z)-1,3,5,8-undecatetraene in Meizhan, suggesting their potential as chemical markers for cultivar authentication. Crude TPS yields ranged from 2.76% to 3.99%; Tieguanyin had the highest yield and Meizhan the lowest. TPS from Daye Wulong exhibited the strongest DPPH and ABTS⁺· scavenging capacities, with IC₅₀ values of 0.58 and 1.95 mg·mL⁻¹, respectively, indicating the highest in vitro antioxidant activity among all tested samples. These results suggest that cultivar genetic background may be a primary determinant of both aroma metabolites and TPS bioactivity, providing a theoretical basis for cultivar selection and quality optimization in oolong tea production.