# Development of Pretreatment Approaches for Authentic Representation of Tea Infusion Aroma
## 3 Results Analysis
### Analysis of Aroma Extraction Efficiency
#### 3.1.2 Comparison of the Peak Area of Important Aroma Substances  
3-Methylbutanal, 2-methylbutanal, linalool, nonanal, decanal, and \(\beta\)-ionone have always been identified as critical aroma compounds in Longjing tea [14; 15; 16; 17]. The effects of extraction conditions on these compounds were further analyzed. Figure 2A reveals that in purified water, 3-methylbutanal, 2-methylbutanal, and their total content increased with higher tea-to-water ratios, while linalool peaked at a 1 g:20 mL ratio before declining. Nonanal fluctuated slightly, whereas decanal and \(\beta\)-ionone decreased. In ion-rich water, 3-methylbutanal and total content rose steadily, while 2-methylbutanal and others remained stable until the 1 g:10 mL ratio, where all compounds surged. At tea-to-water ratios of 1g:10 mL, total aroma content peaked at 92.97% (ion-rich water) and 120.51% (purified water). Further comparative analysis revealed that the variation trends in 3-methylbutanal and 2-methylbutanal content with changing tea-to-water ratios were similar between the two systems, whereas other compounds exhibited divergent trends. This discrepancy may be attributed to ionic interference effects present in the aqueous ion system. As short-chain aliphatic aldehydes, 3-methylbutanal and 2-methylbutanal are derived from the Strecker degradation of leucine and isoleucine, respectively. The observed increase in their concentrations is likely due to the progressive accumulation of dissolved substrate precursors in the tea infusion. The absence of an increasing trend for other compounds in the pure water system may be attributed to either intrinsic concentration-dependent inhibition effects limiting their release or stability, or reduced selective adsorption capacity of SPME fibers at higher concentrations, ultimately resulting in measured content depletion. Figure 2B shows that in purified water, 3-methylbutanal and 2-methylbutanal decreased with temperature, while other compounds and total content increased. High-temperature conditions generally promote the volatilization of aromatic compounds. However, the thermal instability of amino acids at relatively high temperatures may lead to degradation of their precursor substrates required for short-chain aliphatic aldehyde formation, consequently reducing the concentrations of 3-methylbutanal and 2-methylbutanal. In ion-rich water, all compounds and total content except 2-methylbutanal rose. The distinctive behavior of 2-methylbutanal content may be attributed to ionic interference effects, potentially leading to either its reduced concentration or diminished volatility, though the exact mechanism requires further investigation. When the extraction temperature was 60 \({}^{\circ}\)C, the total concentration of volatile compounds peaked in both systems, reaching 91.25% in ionized water and 140.68% in pure water. Figure 2C indicates that in purified water, all compounds except \(\beta\)-ionone increased over time. \(\beta\)-ionone is formed through oxidative degradation or enzymatic cleavage of carotenoids, or alternatively released via hydrolysis of \(\beta\)-ionone glucosides. While its concentration would theoretically increase with prolonged extraction time, the observed plateau after 30 min of extraction may be  
Figure 1: Comparison of total effective peak areas under different extraction conditions of tea aroma compounds (“\({}^{nat}\)” indicates the level of significance. “\({}^{nat}\)” means \(p\) < 0.05; “\({}^{nat}\)” means \(p\) < 0.01; “\({}^{nat}\)” means \(p\) < 0.001; “\({}^{nat}\)” means \(p\) < 0.0001). **(A)** Tea-to-water ratio(“1:50” means 1 g:50 mL; “1:20” means 1 g:20 mL; “1:10” means 1 g:10 mL); **(B)** Extraction temperature; **(C)** Extraction time. attributed to the declining adsorption efficiency of SPME fibers. In ion-rich water, 3-methylbutanal, 2-methylbutanal, and total content peaked at 45 min before declining, while others rose steadily, which likely results from the combined effects of ionic interactions and SPME fiber adsorption dynamics.