Discriminant research for identifying aromas of non‐fermented Pu‐erh tea from different storage years using an electronic nose

Abstract

This study uses an electronic nose to evaluate the aromas of non-fermented Pu-erh tea samples from 10 different storage years (from 2006 to 2015). The samples were analyzed using principal component analysis (PCA), linear discriminant analysis (LDA), and loadings analysis (Loadings) using the Winmuster software system. Of the 10 sensors used, W1 W (sensitive to sulfides), W2 W (sensitive to aromatic components and organic sulfides), W1S (sensitive to methane), and W5S (sensitive to nitrogen oxides) were the most sensitive for dry tea leaves, tea infusions, and infused leaf aroma, and the contribution rates for tea aromas of non-fermented Pu-erh tea were found to be significant. The PCA can differentiate aromas better between dry teas, tea infusions, and infused leaves and is better able to differentiate between tea samples if their storage years are far apart. LDA can differentiate between the aromas of dry teas and the aromas of tea infusions, but it is ineffective in distinguishing the aromas of infused leaves. The results of loadings analysis showed that W1S, W1 W, W2 W, and W5S play a substantial role in discriminating the aromas of non-fermented Pu-erh tea and large changes in the contents of volatile organic sulfides, methane, some aromatic compounds, and nitrogen oxides can occur during the storage of non-fermented Pu-erh tea. The results of this study can help reveal the characteristic volatile components of Pu-erh tea, which provides a theoretical basis for the identification of the aroma qualities of Pu-erh tea and differentiation between storage years. The electronic nose technology is effective in detecting the aroma components of Pu-erh tea. Practical applications The study uses an electronic nose (E-nose) to distinguish the non-fermented Pu-erh tea from different storage years. Using an electronic nose to analyze the characteristic volatile components of Pu-erh tea provides a theoretical basis for distinguishing the tea's different storage years. Although aroma is what is perceived by human's nose, aroma is composed by some chemical volatile components, so E-nose has a certain role so as to identify and analyze aroma of tea, not only through identifying the aroma of Pu-erh tea from different storage years; this method can be applied in building fingerprint data for storage years of tea.