红紫芽熟茶适制性及渥堆发酵过程品质变化研究

目的 研究大叶种特异性品种红紫芽熟茶适制性及渥堆发酵过程中品质变化规律。方法 以红紫芽晒青茶为原料, 分别以高效液相色谱法(high performance liquid chromatography, HPLC)、气相色谱-质谱法(gas chromatography-mass spectrometry, GC-MS)、电子鼻、色差分析结合感官审评方法研究红紫芽熟茶适制性及渥堆发酵过程中品质变化。结果 GC-MS分析结果表明，红紫芽晒青茶共鉴定6大类28种香气物质, 红紫芽出堆样共鉴定出9大类46种香气物质, 电子鼻传感器区别贡献率分析(Loading)结果表明，10个传感器中就有5个传感器(R8、R6、R10、R7和R9)对茶叶香气的响应明显，对区分贡献率最大, 香气分析结果表明红紫芽叶制成熟茶香气物质丰富。随着翻堆序数增加, L*和?L值总体呈下降趋势, a*和?a总体呈增加趋势，b*及?b值随着翻堆序数增加先增加后呈下降趋势, 表明随着发酵进行, 茶汤明亮度降低, 茶汤变红变深, 这与感官呈现的一致。HPLC结果表明，随着渥堆序数增加，总儿茶素、茶多酚及氨基酸含量呈递减趋势, 出堆样氨基酸、茶多酚、总儿茶素含量低于晒青原料(P<0.05), 水浸出物含量高于晒青原料(P<0.05), 每一次翻堆样咖啡碱的含量变化幅度也不大(P>0.05)。感官审评结果表明，红紫芽出堆样汤色棕红明亮，香气陈香、木香带甜香，滋味甜醇尚滑, 品质特征符合普洱茶国家标准。结论 GC-MS及电子鼻香气分析结果表明红紫芽熟茶香气丰富, 品质特征变化符合普洱茶国家标准, 即红紫芽茶适制普洱茶且香气丰富。

Study on the suitability of purple bud post-fermented Pu-erh tea and quality changes during the fermentation process

Objective To study the suitability of purple bud post-fermented Pu-erh tea of large-leaved specific varieties and the pattern of quality changes during the fermentation process. Methods Using purple bud sun-dried green tea as raw material, the quality changes in the pile-fermentation process of purple bud post-fermented Pu-erh tea were studied by gas chromatography-mass spectrometry (GC-MS), electronic nose, color difference analysis combined with the sensory evaluation method. Results A total of 28 aroma substances in 6 categories were identified in the purple bud sun-dried green tea and 46 kinds of aroma substances in 9 categories were identified in the out-of-pile samples of purple buds, and the Loading analysis showed that 5 out of 10 sensors (R8, R6, R10, R7 and R9) responded significantly to the aroma of tea leaves and contributed the most to the differentiation, indicating that the aroma substances in post-fermented Pu-erh tea made from purple buds were abundant. With the increase of the fermentation sequence, the values of L* and ?L showed an overall decreasing trend, a* and ?a showed an overall increasing trend, b* and ?b increased and then decreased with the increase of the fermentation sequence, indicating that as the fermentation progresses, the brightness of the tea soup decreased and the tea soup became redder and darker, which was consistent with the sensory evaluation. The content of total catechins, tea polyphenols and amino acids tended to decrease with the process of pile-fermentation and the content of amino acids and tea polyphenols in the out-of-pile samples was lower than that of sun-dried raw materials (P<0.05), while the content of water extract was higher than that of sun-dried raw materials (P<0.05), and the variation in caffeine content of each turned sample was also not significant (P>0.05). The results of the sensory evaluation showed that the soup color of the purple buds from the pile was brown-red and bright, the aroma was aging, woody and sweet, and the taste was sweet mellow and smooth. Conclusion The aroma of the purple bud post-fermented Pu-erh tea is rich and the quality characteristics conforms to the national standard for Pu-erh tea, that is, the purple bud tea was suitable for post-fermented Pu-erh tea.