基于电子鼻和GC-MS的不同烘焙条件 铁观音品质分析及其鉴别

烘焙对于铁观音乌龙茶的生产极为重要，因为它强烈影响其化学成分和感官品质。为了研究烘焙温度和烘焙时间对铁观音品质的影响，设置不同烘焙条件对铁观音进行焙火处理，并对其进行理化指标的测定，同时采用电子鼻和GC-MS对铁观音的挥发性成分进行检测。结果表明：随着烘焙温度和烘焙时间的增加，3个茶样中的茶多酚、儿茶素、氨基酸等滋味物质均呈逐渐下降趋势，茶多酚含量分别降低4.95%、6.31%和7.66%；儿茶素含量分别降低3.66%、4.33%和5.08%；氨基酸含量分别降低1.19%、1.87%和2.22%。酚氨比由平稳波段而后呈上升趋势，酚氨比分别升高0.34、1.55和2.17，且300 min后的茶叶滋味物质急剧下降，酚氨比急剧上升，气味响应降低，结合感官评价的结果，300 min后烘焙品质下降。电子鼻结果表明，不同烘焙条件和不同烘焙程度的茶叶挥发性物质存在差异。利用电子鼻结合主成分分析、费舍尔判别分析以及多种智能算法能够较好地快速辨别不同烘焙条件以及不同烘焙程度的茶叶。气相色谱-质谱（GC-MS）的气味特征表明，不同烘焙程度的茶叶挥发性物质和香气特征存在显著差异，出现了烤、焦和辛辣的气味。此外，基于偏最小二乘回归（PLSR）的电子鼻与挥发性物质的分析结果揭示了传感器与香气物质之间的内在关系。研究结果为寻找最佳烘焙工艺以及铁观音的品质和香气特征鉴别提供了一种新思路。

Quality analysis and identification of Tieguanyin with different baking treatments based on electronic nose and GC-MS

Roasting is extremely important for the production of Tieguanyin oolong tea, as it strongly affects the chemical composition and sensory quality. In order to analyze the effects of baking temperature and baking time on the quality of Tieguanyin, Tieguanyin was baked under different baking conditions, and the physical and chemical indicators were measured. Futhermore, the volatile components in Tieguanyin were detected by the electronic nose and gas chromatography-mass spectrometry (GC-MS). The results showed that with the increase of baking temperature and baking time, the polyphenols, catechins and amino acids showed gradually decreasing trends, and the contents of polyphenols, catechins and amino acids in three tea samples decreased by 4.95%, 6.31%, 7.66%, 3.66%, 4.33%, 5.08% and 1.19%, 1.87%, 2.22%, correspondingly. The ratio of phenol to ammonia showed an upward trend from a stable band, and the phenol ammonia ratio increased by 0.34, 1.55 and 2.17, respectively. Combined with the results of sensory evaluation, the tea leaves roasted for 300 min were judged to be over-baked, because of the sharply reduced taste substances, the sharply increased the ratio of phenol to ammonia, and the reduced odor response. The electronic nose results showed that the volatile substances in the tea leaves were different in different roasting conditions and different roasting stages. The tea leaves with different roasting