碧香早夏季鲜叶加工乌龙茶过程中品质成分动态变化

以碧香早夏季三四叶鲜叶为原料,按照萎凋、摇青、杀青、揉捻、干燥等工艺加工乌龙茶,对加工过程中的样品和干茶样进行生化成分分析及采用固相微萃取-气质联用(SPME/GC-MS)检测香气成分,并结合感官审评探讨碧香早鲜叶加工乌龙茶过程中品质成分动态变化及品质形成分析。感官审评结果表明,乌龙茶滋味醇和,香气带花香。品质成分分析表明,茶多酚、儿茶素、咖啡碱、可溶性糖、黄酮、水浸出物等成分总体呈现下降的趋势,从鲜叶到干茶分别下降了5.32%、3.96%、0.48%、0.38%、22.35%、2.77%,游离氨基酸的含量总体呈现上升的趋势,相较于鲜叶干茶的含量升幅为12.88%。挥发性成分分析结果表明,碳氢类、酮类、醛类及其他类物质总体含量呈现上升的趋势,而醇类、酯类、酚类物质含量总体呈现下降趋势。其中,反式-橙花叔醇、苯乙醇、二氢芳樟醇、苯甲醛、β-紫罗酮、吲哚、α-法呢烯、α-依兰油烯、香叶基丙酮等成分可作为夏季碧香早乌龙茶的特征香气成分。乌龙茶加工促使具苦涩味及青气物质逐渐减少、甜醇及花果香类物质逐渐增加,有利于茶汤滋味及香气的形成,为夏季茶资源利用提供科学的参考。

Dynamic Changes in Quality and Composition of Oolong Tea Made with Fresh Bixiangzao Summer Tea Leaves during Processing

Using three-four fresh leaves of Bixiangzao summer tea leaves as the raw materials,oolong tea was produced following the procedure involving withering,shaking,kill-green(de-enzyming),rolling and drying steps.The biochemical components of the samples generated from the tea processing and the dry tea samples were analyzed,and the aroma components were detected by solid phase microextraction-gas chromatography-mass spectrometry(SPME/GC-MS).Combined with sensory evaluation,the dynamic changes of quality components and quality formation of Bixiangzao fresh leaves during oolong tea processing were examined.The results of sensory evaluation showed that the oolong tea had amellow taste and a floral aroma.Quality component analysis showed that tea polyphenols,catechins,caffeine,soluble sugars,flavonoids and water extracts showed an overall downward trend(decreases by 5.32%,3.96%,0.48%,0.38%,22.35%and 2.77%,respectively,from fresh leaves to dried tea),whilst the content of free amino acidsshowed an overall upward trend(an increase by 12.88%from fresh leaves to dried tea).The analysis of volatile components revealed that the overall contents of volatile components(hydrocarbons,ketones,aldehydes and other substances)showed an upward trend,whilst the contents of alcohols,esters and phenols showed an overall downward trend.Among them,trans-nerol,phenylethanol,dihydrolinalool,benzaldehyde,β-ionone,indole,α-farnesene,α-ylenoleneand geranyl acetone can be used as the characteristic aroma components of Bixiangzao summer oolong tea.The processing of oolong tea promotes the gradual decrease of bitter and astringent tastes and greenish substances,and the gradual increase of sweet,mellow,and floral and fruity substances,which is conducive to the formation of the taste and aroma of this kind of tea,and provides a scientific reference for the utilization of summer tea resources.