The effect of gibberellins on tea leaf chemical composition and quality was investigated. The results showed that application of gibberellins was beneficial to green tea quality. Content of amino acids increased by 9-8% and that of vitamin C by 17.8% and tea catechins index increased by 12.9%. The content of tea polyphenols and ratio of tea polyphenols to amino acids decreased by 9.9% and 11.5%, respectively. Differences of all the indicators were statistically significant (P<0.05). Quality scores of the treated leaf increased significantly (P<0.05). It was also revealed that tea plant response to gibberellins was dependent not only on genetics, but also on shoot development stage.

△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.

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.

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.