电子鼻技术对普洱熟茶香气判别的研究
Discriminant Research for Identifying Aromas of Post-Fermented Pu-Erh Tea from Different Storage Years Using an Electronic Nose

采用电子鼻技术对10个不同贮藏年份（2006-2015年）普洱熟茶的香气进行了研究.通过电子鼻Winmuster软件自带的模型识别方法进行主成分分析（PCA）、线性判别分析（LDA）和传感器区分贡献率分析（Loadings），对不同年份普洱熟茶的干茶、茶汤和叶底的香气进行分析和识别.结果表明：10个传感器中，W1W（对硫化物敏感），W2W（对芳香成分、有机硫化物敏感）、W1S（对甲烷敏感）和W2S（对乙醇敏感）对干茶香气灵敏度较高；W1W，W2W，W1S，W5S（对氮氧化合物敏感）对茶汤和叶底香气灵敏度较高，对普洱熟茶香气测定的贡献率较大；PCA和LDA能很好地区分不同贮藏年份普洱熟茶干茶、茶汤和叶底的香气，且年份差别越大，分离效果越好.Loadings结果分析显示：传感器中W1S，W1W，W2W和W2S在普洱熟茶香气判别中起主要作用，表明普洱熟茶储藏期间其挥发性有机硫化物、甲烷、部分芳香型化合物和乙醇类物质可能发生了较大变化.研究结果表明，电子鼻技术在普洱茶香气的检测领域具有较强的可操作性，同时为普洱熟茶的香气品质判别以及年份鉴定提供了理论依据.
In a study reported in this paper, an electronic nose was used to evaluate the aromas of post-fermented pu-erh tea samples from 10 different storage years (from 2006 to 2015). The samples were analyzed with principal component analysis (PCA), linear discriminant analysis (LDA) and loadings analysis (Loadings) using the Winmuster software system. Of the 10 sensors used, W1W (sensitive to sulfides), W2W (sensitive to aromatic components and organic sulfides), W1S (sensitive to methane) and W2S (sensitive to ethanol) were the most sensitive for dry tea leaves, the sensitivity of W1W, W2W, W1S and W5S (sensitive to nitrogen oxides) to tea infusion and infused leaf aroma was higher, and their contribution rates for tea aromas of post-fermented pu-erh tea were found to be significant. PCA and LDA could well differentiate aromas between dry teas, tea infusions and infused leaves and were better able to differentiate between tea samples if their storage years were far apart. The results of loadings analysis showed that W1S, W1W, W2W and W2S played a substantial role in discriminating the aromas of post-fermented pu-erh tea and large changes in the contents of volatile organic sulfides, methane, some aromatic compounds, and ethanol material occurred during its storage. The results of this study showed that the electronic nose technology is effective in detecting the aroma components of pu-erh tea