A study on chemical estimation of pu-erh tea quality

Chemical compositions and infusion colour differences of seven pu-erh tea samples and their correlation to sensory quality were investigated. The results showed that the pu-erh tea contained 37.1 mg g(-1) caffeine, 15.7 mg g(-1) amino acids, 67.0 mg g(-1) polyphenols and 8.41 mg g(-1) total catechins, on average. Among the 17 tested volatile compounds, n-valeraldehyde was not detected. The most abundant volatile was beta-ionone and the next was linalool oxide II. Infusion colour analysis showed that the pu-erh tea had deep hue with DeltaE ranging from 66.8 to 79.2. Spearman's linear correlation analysis showed that total quality score (TQS) of the pu-erh tea was significantly correlated to concentration of amino acids, linalool oxide II and infusion colour indicator DeltaE. Five components were extracted from the 34 tested indicators by principal component analysis and were regressed on the TQS to produce six Pearson's linear regression equations for estimating sensory quality of pu-erh tea, among which two were statistically significant, ie TQS = 57.47 - 0.18geraniol + 0.33polyphenols - 1.14n-caproaldehyde - 1.38linalool oxide I + 0.21caffeine (p < 0.01) and TQS = 57.42-0.03Citral + 0.33polyphenols - 1.14n - caproaldehyde - 1.40linalool oxide I + 0.20caffeine (p < 0.01). (C) 2004 Society of Chemical Industry.