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.

The colour differences in terms of △L, △a, △b and △E between distilled water and infusions of 29 green teas, 16 black teas and 13 oolong teas and their correlation with sensory quality attributes of tea were investigated. The results showed that the △L value decreased but the △a, △b and △E increased with the degree of fermentation of the three kinds of tea. The △L was positively correlated to quality attributes of green tea and oolong tea but negatively correlated to those of black tea. The △a of tea infusions is a reliable descriptor to differentiate among green and black teas. The regression of total quality score of green tea (TQSg) upon the △a was TQSg=−2.26△a+77.2 (R2=0.22, p <0.01), that of total quality score of black tea (TQSb) upon △b was TQSb=0.70△b+44.6 (R2=0.31, p<0.05) and that of total quality score of oolong tea (TQSo) upon △L was TQSo=1.09△L+94.5 (R2=0.75, p<0.01). Because the infusion colour difference indicators of △a, △b and △L can be done rapidly, it could be very useful for on-site or on-line quality monitoring during tea manufacture and storage.

△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.

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.