## 3 Results and Discussion
### Key Odorants in RZT Identified by OAV Analysis  
As is well acknowledged, not all volatile compounds contribute to the aroma of tea. The quality and type of tea aroma are determined by the complex interaction of various volatile compounds at different concentrations, each with its own aroma contribution [15]. It is therefore insufficient to assess the contribution of aroma compounds to the aroma quality of tea just based on their content solely. The odor activity value (OAV) of a volatile reflects its influence on the overall aroma quality of tea; a compound with an OAV greater than 1 is typically considered a key odorant to the aroma and could help determine the overall aromatic quality [36]. Consequently, this study involved determining odor thresholds and calculating OAVs for 112 volatiles detected by GC-MS in order to screen out the key odorants that substantially influence the aroma quality of RZT. Table 1 presents the final computational and screening results. Out of the 45 volatiles analyzed, 26 were found to have OAVs greater than 1. These volatiles comprised seven aldehydes, two alkenes, six ketones, three esters, five alcohols, one oxygen heterocycle, one nitrogen heterocycle, and one aromatic. In terms of the aroma distribution of volatile compounds with an OAV > 1, the distinctive aroma profiles of RZT were characterized as floral (nine volatiles), fruity (five volatiles), and aldehyde (three volatiles), with cumulative OAVs of 2206.37, 121.74, and 250.85, respectively.  
It is a well-established fact that a volatile compound can significantly influence the overall flavor profile of tea when its OAV exceeds 100 [37]. Among the identified volatiles, three volatiles had OAVs > 100, indicating their pivotal roles in the aroma of RZT: (E)-\(\beta\)-ionone (OAV = 1625.22), followed by phytol (OAV = 395.95), and decanal (OAV = 167.53). Notably, decanal is characterized by its fatty odor and is recognized as a key aroma compound in Chinese chestnuts [14; 38]. Consequently, decanal is presumed to have a substantial effect on the chestnut-like aroma of RZT. Among other volatiles with OAVs > 10 in RZT, 3,5-octaleri-2-one (OAV = 98.57) exhibits a fruity odor and is confirmed as a key odorant of Longjing tea [39]. Hexanal, heptanal, octanal, nonanal, 1-octene-3-ol, (Z)-jasmone, and jasmine lactone are primarily produced through the degradation of fatty acids [6], while \(\beta\)-Cyclocitral, (E)-\(\beta\)-ionone, \(\alpha\)-ionone, and nerolidol are aromatic compounds derived from carotenoid cleavage [16]. Additionally, there exists a positive correlation between the quality of the chestnut-like aroma and the levels of (E)-\(\beta\)-ionone and nerolidol [40]. Other volatiles with OAVs > 1 include D-limonene, 1-octen-3-ol, 2-pentylfuran, hexanoic acid, methyl ester, methyl salicate, indole, and (E)-\(\beta\)-ocime, which have been identified as characteristic or aroma-active compounds in tea [7; 15; 41; 42; 43]. Additionally, previous research has indicated  
Figure 3: Effects of low-temperature stress on volatiles in fresh leaves of RZT (speculated). LOX: lipoxygenase; HPL: hydroperoxide lyases; AOS: allene oxygenase; JMT: JA carboxyl methyltransferase.  
that D-limonene, 2-pentylfuran, and (E)-\(\beta\)-ocimene are the common aroma compounds of curled and pelleted RZT [44].  
While research on the OAVs of tea volatiles has advanced, the limitations of OAV analysis have become increasingly apparent. For instance, certain volatiles exhibit a disproportionate relationship between their intensity and concentrations [7]. Moreover, the OAV alone is inadequate for accurately ranking the contributions of volatiles to a specific flavor profile. Some volatiles with lower OAVs might still be crucial to the overall flavor [45; 46; 47]. Consequently, to enhance OAV analysis, GC-O analysis which incorporates instrumental analysis and sensory determinations needs to be employed.