Characteristics and chemical compositions of Pingwu Fuzhuan brick-tea, a distinctive post-fermentation tea in Sichuan province of China

Pingwu Fuzhuan brick tea (PWT), a distinctive post-fermentation tea originated from Pingwu region of Sichuan province in China, is a popular “western road” border-selling tea. In this study, we investigated characteristics and chemical compositions of PWT, together with comparing its physicochemical properties with other regions of Fuzhuan brick teas (FBTs). Firstly, inductively coupled plasma mass spectrometry (ICP-MS) was used to determine the geographical origin of FBTs, and the profiles of mineral elements were subjected to principal component analysis (PCA) to evaluate the differences among FBTs. Results from ICP-MS showed that the compositions of mineral elements from PWT, Hunan FBT (HNT), Shaanxi FBT (SNT), and Guizhou FBT (GZT) were distinctly different. The four different types of FBTs were clearly distinguished according to the results of PCA. Furthermore, all FBT samples were assessed for physicochemical properties and heatmap method was applied to data analysis. It was found that the total colour difference was highly distinct when compared PWT with HNT, SNT and GZT. Moreover, most of contents of biochemical compounds (gallic acid, catechins, free amino acids, alkaloids and volatile components) in PWT were lower compared to others except for total essential amino acids, GABA, aldehydes and acids.