基于UPLC-Q-Exactive Orbitrap-MS分析不同足火方式对绿茶中叶绿素降解的影响

探索不同足火方式（远红外足火、微波足火、提香机足火、理条足火、六角辉锅足火）对绿茶色泽和叶绿素降解的影响。建立基于超高效液相色谱-四极杆-静电场轨道阱高分辨质谱联用技术分析茶叶中叶绿素组分及其降解衍生物方法，可在20 min内检测19 种叶绿素及降解组分，并较好分离6 对差向异构体，且预处理简单。将该方法用于5 种不同足火方式所制绿茶中叶绿素及其降解组分的检测分析，并结合正交偏最小二乘法判别分析及单因素方差分析，探究不同足火方式对绿茶叶绿素降解的影响。结果显示，微波足火所制绿茶色泽感官品质和色泽属性均优于其他足火方式。微波足火所制得绿茶中叶绿素a、叶绿素b、叶绿素a’、叶绿素b’等含量最高，而降解产物焦脱镁叶绿酸a、焦脱镁叶绿酸b、焦脱镁叶绿素a、焦脱镁叶绿素b含量最低，表明微波足火过程中绿茶发生异构化、脱镁降解反应、脱羧甲基化反应的程度均低于其他足火方式，故微波足火更有利绿茶中叶绿素的保留。本研究可为绿茶品质提升和定向化加工提供理论基础和技术指导。

Effects of Different Full Drying Methods on the Chlorophyll Degradation in Green Tea as Analyzed by UPLC-Q-Exactive Orbitrap-MS

This study is aimed to explore the effects of different full drying methods (far infrared, microwave, re-drying, carding, and rotary pot full drying) on the color and chlorophyll degradation of green tea. A method for the analysis of chlorophylls and their degradation derivatives in tea was established based on ultra-high performance liquid chromatography quadrupole orbitrap high resolution mass spectrometry (UPLC-Q-Exactive Orbitrap-MS). A total of 19 chlorophylls and degradation derivatives were detected within 20 min, and six pairs of epimeric chlorophylls and chlorophyll derivatives were well separated with simple sample pretreatments. For the purpose of the present study, this method was applied to analyze chlorophylls and their degradation products in green tea samples manufactured by the five different full drying methods, and the data were analyzed by orthogonal partial least square-discriminant analysis (OPLS-DA) and one-way analysis of variance (ANOVA). The results showed that compared to the other full drying methods, green tea prepared by microwave full drying had better sensory color and quality. The contents of chlorophyll a (Chl a), chlorophyll b (Chl b), chlorophyll a’ (Chl a’) and chlorophyll b’ (Chl b’) were the highest in green tea prepared by microwave full drying, while the contents of pyropheophorbide a (PyrPo a), pyropheophorbide b (PyrPo b), pyropheophytin a (PyrPhe a) and pyropheophytin b (PyrPhe b) were the lowest, indicating that microwave full drying resulted in the lowest degree of isomerization, magnesium removal and degradation reaction and decarboxymethylation. Therefore, microwave full drying is more beneficial to the protection of chlorophylls in green tea. This study can provide a theoretical basis and technical guidance for quality improvement and directed processing of green tea.