Effect of Altitude on the Quality of Different Types of High Mountain Green Tea

The growth of tea trees was significantly influenced by the ecological environment, and the quality of tea varies notably under different cultivation conditions, with altitude playing a key role. High mountain green teas (Longjing and Yunfeng) cultivated at 500 m and 900 m altitudes were selected as the focal specimens in this research. By measuring their main physicochemical indicators, volatile components, and sensory evaluations, the impact of altitude on tea quality were analyzed. The results showed that as the altitude increases from 500 m to 900 m, the content of catechins in both Longjing and Yunfeng significantly decreased (P<0.01). The contents of tea polyphenols, the ratio of phenols to amino acids, and water extractives decreased by 4.35% and 8.3%, 0.29 and 0.24, and 0.91% and 2.3%, respectively, with significant decreased in tea polyphenol content and the phenol to amino acid ratio (P<0.05). The total flavonoid content of both high mountain green teas showed no significant change at the two altitudes. The content of theanine in Longjing increased with altitude, rising by 0.03%, while the content of theanine in Yunfeng significantly decreased with altitude (P<0.05), dropping by 0.39%. In terms of volatile components, the OPLS-DA model analysis identified key aroma components such as 4-methyl-4-penten-2-one and 6-vinyl-2,2,6-trimethyl-2H-pyran-3-ol, which showed significant differences in content in tea leaves from different altitudes. Nonanal, D-limonene, and benzaldehyde were found to be present in higher concentrations in tea leaves at an altitude of 900 m, which significantly impacted the aroma quality of the tea. Sensory evaluation indicated that the aroma of high mountain green tea at 900 m altitude was more intense, and the taste was fresher, which was consistent with the analysis results of the aroma components. In summary, altitude had a significant impact on specific quality indicators of the two types of high mountain green tea, with the low temperature, high humidity, and misty environment of high-altitude areas contributing to the improvement of the aroma and taste of the tea. This provides a scientific basis for optimizing tea cultivation conditions and enhancing tea quality.