Chemical composition of two beverage plant species, i.e. Ilex latifolia and Camellia sinensis were investigated. Fifteen and sixteen amino acids were detected in I. latifiolia and C. sinensis, respectively. Major amino acids were histidine, aspartic acid and glutamic acid in I. latifolia but theanine, glutamic acid and histidin in C. sinensis. Ascorbic acid and polyphenols in I. latifiolia were 0.46 mg g-1 and 90.1mg g-1, less than one fourth and one half of those in C. sinensis, respectively. Eight catechin compounds were found in C. sinensis but only four in I. latifolia, i.e. l-catechin (C), l-epicatechin (EC), l-epicatechin gallate (ECG) and l-catechin gallate (CG). Three flavonoids, i.e. rutin, mericetin and quercetin were detected and their total contents in I. latifolia and C. sinensis were 4781mg kg-1 and 580 mg kg-1, respectively. Caffeine was not detected in I. latifolia. The higher concentration of flavonoids in leaf of I. latifolia may be related to its value for a healthy beverage.

Tea cream and haze in black tea infusions increased with the rise in the tea extraction temperature. The temperature at which substances involved in cream and haze formation began to be extensively extracted into the tea infusion was between 50and 60℃. The tea cream particle volume concentration in infusions extracted at 50℃ or below formed less tea cream particles, and their particle sizes were larger and more heterogeneous than those extracted at 60℃ and second infusions extracted at 90℃ from the residual leaves that were previously extracted at 40-50℃. High-performance liquid chromatography confirmed that constituents with pyrogallol groups are involved in tea creaming, and the effect of caffeine on tea cream and haze depends on whether these constituents are sufficiently present. The extractability of tea increased with the rise in extraction temperature. Twostage extraction of tea in ready-to-drink tea processing and its effects on colorimetric indicators were also examined.

△L, △a, △b and △E were significantly correlated to total quality score (TQS). The parameters correlating significantly with the TQS were classified into four groups. Group 1 was compounds containing nitrogen, group 2 phenol compounds, group 3 tea pigments and group 4 infusion colour indicators. Four principal components were screened from the four groups as independent variables for constructing regression equations for estimation of black tea quality by principal component analysis. The regression of the TQS upon the principal components gives a highly significant relationship.

Particle size, concentration and chemical composition of green-tea cream and black-tea cream were studied. Tea-cream particle size tended to decrease during tea fermentation and average size of tea-cream particles was bigger for green than for black tea. The amount of tea-cream formed in tea infusions depended on their chemical composition. Tea catechins and their oxidation products formed tea-cream when they interact with some non-catechin compounds in tea liquor. Model fermentation tests revealed that little tea-cream was found in solution of crude tea catechins and the tea-cream formed after fermentation did not significantly increased in the crude tea catechins solution. Tea extract prepared at 50℃ formed less tea-cream than those prepared at 90℃ before and after fermentation. Caffeine, gallocatechin (GC) and epigallocatechin gallate (EGCG) were the predominant compounds in green-tea cream but thearubigins (TRs), caffeine and theaflavins (TFs) in black-tea cream. Gallated catechins and gallated TFs had stronger creaming ability than un-gallated catechins and TF. How to control tea liquor from creaming down is discussed.

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 37.1mg g−1 caffeine, 15.7mg g−1 amino acids, 67.0mg g−1 polyphenols and 8.41mgg−1 total catechins, on average. Among the 17 tested volatile compounds, n-valeraldehyde was not detected. The most abundant volatile was β-ionone and the next was linalool oxide II. Infusion colour analysis showed that the pu-erh tea had deep hue with △E 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 △E. 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−1.38linalooloxideI+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).