Harvesting Time-Dependent Variations in Volatile Compounds and Key Aroma-Active Components of Shaanxi Langao Green Tea

To investigate the effect of harvesting time on the aroma quality of Langao green tea, volatile compounds in tea leaves collected in early, middle, and late spring were analyzed using stir bar sorptive extraction coupled with gas chromatography-mass spectrometry (GC-MS). Multivariate statistical analysis and odor activity value (OAV) were applied to systematically identify key differential volatile compounds and aroma-active components. A total of 109 volatile compounds were identified, among which terpenes, alcohols, esters, and ketones were the main ones, collectively accounting for 69% of the total volatile content. Principal component analysis, partial least squares-discriminant analysis, and non-parametric tests revealed 23 key differential compounds (P < 0.05) including cis-linalool oxide (furanoid), linalool, cedrol, and 2-methylbutanal, common across different harvesting periods. Based on absolute quantification and OAV analysis, six key aroma-active components (OAV ≥ 1) were identified: 2-methylbutanal, 1-octen-3-one, linalool, α-cubebene, cedrol, and safranal. Among these, linalool and α-cubebene reached the highest concentrations in middle spring, whereas safranal peaked in late spring. These compounds could be used as important indicators for distinguishing Langao green tea from different harvesting periods. This study provides a theoretical foundation for the precise harvesting and quality control of spring tea. Furthermore, it offers potential strategies for enhancing tea quality through targeted modulation of these key aroma compounds.