黑茶陈化过程中品质形成机理研究及黑茶年份推测模型构建

Chinese tea broadly fall into six categories, dark tea is a member of the Chinese tea. The longer the dark tea has been stored，the better the quality， the price of the old dark tea also improved. Deep analysis and systematic study on quality formation of aging mechanism of dark tea has great significance in theory and practice.In order to study the aging mechanism of dark tea， organoleptic evaluation will be carried out for different years dark tea. Purpose to investigate the quality characteristic and difference between the samples which is in different storage time， the appearance， internal quality， chromatic aberration and the species and amount of microbes of different samples was analyzed and compared.To explore the rules of quality components changes during the aging process， variations of the chemical components (tea Polyphenols， water extract， free amino acids， caffeine， catechins，organic acid，theaflavins) and sensor qualities were studied and examined. The quality of the tea samples were also compared by sensory evaluation and the volatile constituents were investigated by gas chromatograph/mass spectrometer (GC-MS). The aroma components of dark tea in different years were extracted with SDE method and analyzed by GC-MS. Depend on the acquired complete NIRS spectrum information of dark tea samples，construct mathematical models by mathematical methods which can fully represent the characteristics of whole spectrum and exclusive attributes of the dark tea samples．This study provides a reference to drinking tea properly， raising rational consumption and investment of dark tea.

黑茶是中国六大茶类的一类,随贮藏时间延长“越陈越香”，陈年黑茶价值较新茶成倍提升。因此，深入探讨黑茶陈化过程中品质变化情况，科学揭示黑茶“越陈越香”品质的形成机制，具有重要的理论研究价值和现实意义。为阐释黑茶陈化机理，项目将对不同年份黑茶进行感官审评，从外形、内质、色差等角度探讨不同年份黑茶的感官品质特征。测定水浸出物、多酚总量，水溶性氨基酸、儿茶素、生物碱、有机酸、茶黄素等品质成分的组成及含量，了解它们在陈化过程中变化规律。采用气-质法(GC-MS)测定挥发性香气成分，近红外光谱技术(NIRS)提取茶叶全光谱信息，利用主成分分析、聚类分析等化学计量方法对香气和近红外光谱特征进行分析，构建基于香气成分和红外光谱特征的黑茶年份推测模型，为黑茶年份（区间）推断提供参考依据。研究结果将进一步丰富黑茶陈化过程中品质转化的理论研究体系，为科学饮用黑茶，引导市场理性消费、投资黑茶提供参考。

黑茶是六大茶类中唯一具有“越陈越香”特征的茶类，陈年黑茶价值较新茶成倍提升。本项目对黑茶感官审评方法进行了研究；对不同年份86份黑茶样品感官品质、水浸出物含量、主要滋味成分（茶多酚含量、游离氨基酸含量、水溶性糖含量、儿茶素组分及其含量、生物碱组分及其含量、18种氨基酸组分及其含量、7中有机酸组分）及香气成分进行了分析、比较；采用偏相关方法探讨了各品质成分与储存年份的相关性；构建基于主成分分析法的年份预测模型。 试验结果表明：100℃沸水，1:50茶水比，冲泡8min，能制备浓度适中，较适合制备适合内质评价的湖南黑茶茶汤，此方法能够较客观地反映茶叶的品质优劣。随着储存年份延长，干茶色泽褐变，茶条逐渐松散，青气褪而陈香显，滋味出现醇化的趋势；原料、工艺、仓储良好的茶叶转化较好，渥堆程度重的黑茶转化差异小。不同类别黑茶滋味成分陈化趋势不一，整体表现为水浸出物、茶多酚、游离氨基酸、EGC、DL-C、EGCG、GCG、咖啡碱、乳酸的含量均呈弱线性降低趋势；水溶性糖、总生物碱、EC、苹果酸、谷氨酸、苏氨酸、脯氨酸、胱氨酸虽随陈化稍有下降，但不构成线性趋势，其余常规品质成分无明显的整体变化现象。不同茶类香气成分组成及含量随储藏年份变化的情况各不相同，构成独特的香气类型。陈化过程中以果香、花香和木香为主的醇类、醛类、酮类物质增加，得到1-己醇、2-乙基己醇、2,6-二甲基环己醇、雪松醇、异植醇等23种陈茶共有的特征性香气物质；得到新茶共有的特征性香气物质吡咯；未发酵茶叶特有的陈香物质（2Z）-2-戊烯-1-醇。构建出以相关品质成分为依据的黑茶年份预测模型：Z=0.4207*Z1+0.1964*Z2+0.1156*Z3+0.0849*Z4。本项目研究结果为揭示黑茶“越陈越香”品质的形成机制提，为黑茶品质形成体系研究提供了参考。