绿茶及红茶中游离氨基酸对映异构体的分布特征及呈味特性  

Distribution and Taste Characteristics of Free Amino Acid Enantiomers in Green Teas and Black Teas

作　　者：李玮轩 邵晨阳[1] 严寒 张悦[1] 吕海鹏[1] 林智[1] 朱荫 LI Weixuan;SHAO Chenyang;YAN Han;ZHANG Yue;L Haipeng;LIN Zhi;ZHU Yin(Key Laboratory of Tea Biology and Resource Utilization of Ministry of Agriculture and Rural Affairs,Tea Research Institute,Chinese Academy of Agricultural Sciences,Hangzhou 310008,China;College of Food and Health,Zhejiang Agriculture and Forestry University,Hangzhou 311300,China)

机构地区：[1]农业农村部茶树生物学与资源利用重点实验室/中国农业科学院茶叶研究所,浙江杭州310008 [2]浙江农林大学食品与健康学院,浙江杭州311300

出　　处：《食品科学技术学报》2024年第5期51-67,共17页Journal of Food Science and Technology

基　　金：国家自然科学基金资助项目(32172631);现代农业产业技术体系建设专项(CARS-19);中国农业科学院创新工程项目(CAAS-ASTIP-2014-TRICAAS)。

摘　　要：茶叶中大部分游离氨基酸具有滋味特征及阈值迥异的对映异构体,查明绿茶及红茶中各游离氨基酸对映异构体的分布特征及其对茶汤滋味的贡献,有助于丰富茶叶化学知识体系,为茶叶滋味品质的提升与定向调控提供理论依据。采用酯化-五氟丙酰化法结合手性气相色谱-质谱联用技术(gas chromatography-mass spectrometry,GC-MS)查明了10种绿茶及8种红茶中的15对重要游离氨基酸对映异构体的分布特征;采用浓度模拟及定量描述分析法,探明了各游离氨基酸对映异构体的呈味特性,并初步揭示了各氨基酸对映异构体对绿茶及红茶茶汤滋味的影响。分析结果表明,L-谷氨酸混合物、L-酪氨酸、L-丝氨酸在绿茶和红茶中存在显著性差异(P<0.05),其中L-酪氨酸与L-丝氨酸在红茶中的含量显著高于绿茶,而L-谷氨酸混合物则呈现相反的分布趋势。定量描述分析结果表明,各对映异构体主要呈现鲜、甜、苦、硫黄等滋味特征,L-谷氨酸(鲜)、L-色氨酸(苦)、L-谷氨酰胺(鲜)、D-色氨酸(甜)等呈味强度最高;同一氨基酸的不同对映异构体可能呈现截然相反的滋味特征,如色氨酸、苯丙氨酸、酪氨酸及亮氨酸的D-异构体呈现愉悦的甜味特征,而L-异构体呈现较为明显的苦味。氨基酸模拟液与绿茶茶汤的滋味审评结果表明,L-谷氨酸、L-谷氨酰胺及L-天冬氨酸可能对绿茶的鲜味特征起到较为重要的作用,L-丙氨酸及D-苯丙氨酸可能对绿茶的甜味特征起到一定促进作用,而L-苯丙氨酸及L-色氨酸可能参与绿茶苦味特征的形成;以上氨基酸对映异构体同样可能对红茶的滋味形成起到重要作用,而L-丝氨酸及L-酪氨酸等对红茶的甜味和苦味有一定贡献。Most free amino acids in teas have enantiomers with different odor characteristics and threshold values.Identifying the distribution characteristics of free amino acid enantiomers in green teas and black teas and their detailed contribution on the formation of tea taste could enrich the knowledge system of tea chemistry and provide a theoretical foundation for the improvement and directional adjustment and control of tea taste quality.Esterification pentafluoropropionyl(PFP)acylation combined with gas chromatography-mass spectrometry(GC-MS)was applied to analyzed 15 pairs of important free amino acid enantiomers in 10 green teas and 8 black teas.The taste characteristics and preliminary contributions on the taste of green tea and black tea infusion of various enantiomers of free amino acids were investigated by concentration simulation and quantitative descriptive analysis.Analysis results indicated L-glutamic acid(mixture),L-tyrosine and L-serine were the key differential enantiomers between two types of teas(P<0.05),of which the contents of L-tyrosine and L-serine in black teas were obviously higher than that in green teas,while L-glutamic acid(mixture)exhibited the reverse distribution trends.The quantitative descriptive analysis results indicated that umami,sweet,bitter and sulphur were the main taste characteristics of the free amino acid enantiomers,and L-glutamic acid(umami),L-tryptophan(bitter),L-glutamine(umami)and D-tryptophan(sweet)showed the strongest taste intensities.The two enantiomers of the same amino acids might present the completely opposite taste characteristics,e.g.the D-enantiomers of tryptophan,phenylalanine,tyrosine and leucine presented a pleasant sweet taste,while a strong bitterness was received by their L-enantiomers.The taste sensory results of amino acid simulated solution and green tea infusion demonstrated that L-glutamine,L-glutamic acid and L-aspartic acid might contribute to the umami taste of green teas,L-alanine and D-phenylalanine might promote the sweet characteristic,and L

关 键 词：绿茶 红茶 游离氨基酸 对映异构体 滋味贡献 

分 类 号：TS272.2[农业科学—茶叶生产加工]