Jian-Liang Lu

Estimation of black tea quality by analysis of chemical composition and colour difference of tea infusions

Abstract Chemical composition, colour differences of black tea infusions and their relationships with sensory quality assessed by tea tasters were analysed. There were significant correlations between the individual quality attributes. Content of caffeine, nitrogen, amino acids, polyphenols, gallocatechin (GC), epigallocatechin (EGC), catechin (C), epicatechin (EC), epicatechin gallate (ECG), catechin gallate (CG), total catechins, theaflavin (TF) and theaflavin-3′-gallate (TF3′G) and infusion colour indicators of Δ L , Δ a , Δ b and Δ 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.

Comparison of chemical compositions of Ilex latifolia Thumb and Camellia sinensis L.

Abstract 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 90.1 mg 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 4781 mg 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.

Using tea stalk lignocellulose as an adsorbent for separating decaffeinated tea catechins.

Lignocelluloses prepared from woody tea stalk, pine sawdust and sugarcane bagasse were used as adsorbents to isolate decaffeinated catechins from tea extracts and compared with synthetic macroporous resin HPD 600. HPD 600 had the highest adsorption capacity to catechins, followed by tea stalk lignocellulose while lignocelluloses of pine sawdust and bagasse the least. Tea stalk lignocellulose absorbed preferentially tea catechins and showed a good selectivity. HPD 600 absorbed caffeine and tea catechins simultaneously. The kinetics data of tea stalk lignocellulose showed a good fit with the Langmuir isotherm model. It is considered that tea stalk lignocellulose is an alternative low-cost adsorbent for preparing decaffeinated tea catechins.

Green tea polyphenols attenuating ultraviolet B-induced damage to human retinal pigment epithelial cells in vitro.

PURPOSE To examine the protective effect of green tea polyphenols against ultraviolet B (UVB)-induced damage to retinal pigment epithelial (RPE) cells. METHODS Green tea polyphenols (GTP) was used to treat RPE cells before or after exposure to UVB. Viability of RPE cells was tested by 3,(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. Survivin gene expression was examined by real-time PCR analysis. Ultrastructure of RPE cells was examined by transmission electron microscopy. RESULTS GTP effectively suppressed the decrease in viability of the UVB stressed RPE cells and the UVB suppression of survivin gene expression level. GTP alleviated mitochondria dysfunction and DNA fragmentation induced by UVB. CONCLUSIONS GTP protected RPE cells from UVB damage through its increase in the survivin gene expression and its attenuation of mitochondria dysfunction and DNA fragmentation. GTP is a potential candidate for further development as a chemoprotective factor for the primary prevention of age-related eye diseases such as age-related macular degeneration.

Chemical and Instrumental Assessment of Green Tea Sensory Preference

Parameters of liquor color difference, taste related constituents and aroma related volatiles in 23 Chinese green tea (Camellia sinensis) samples were analyzed by color difference meter, high performance liquid and gas chromatographs respectively. Seven variables were extracted by principal component analysis from the data sets corresponding to the liquor color, taste and aroma and linear regression of total score of sensory preference (TSSP) upon the 7 extracted variables produced a significant relationship: TSSP = 105.82–0.56 (ΔE)−0.15 (total catechins) + 0.32 (geraniol) + 0.53 (GCG) + 0.44 (linalool oxide I) −0.54 (ascorbic acid) + 0.24 (n-valeraldehyde) (p = 0.003, standard error of the estimation = 2.97). The regressive relationship simplifies the process of chemical and instrumental assessment of sensory preference of green tea and could be used for green tea quality assessment.

Adsorption Behavior of the Catechins and Caffeine onto Polyvinylpolypyrrolidone

Adsorbent is one of the most important factors for separation efficiency in fixed-bed purification techniques. The adsorption behavior of catechins and caffeine onto polyvinylpolypyrrolidone (PVPP) was investigated by static adsorption tests. The results showed that catechins rather than caffeine were preferred to adsorb onto PVPP since the adsorption selectivity coefficient of total catechins vs caffeine was around 22.5, and that adsorption of catechins could be described by the pseudo-second-order model. Adsorption amount of caffeine onto PVPP in green tea extracts solution was much higher than that in purified caffeine solution although the initial concentration of caffeine was similar in the two solutions, indicating the caffeine might be attached with catechins which were adsorbed by PVPP instead of being adsorbed by PVPP directly. The results also showed that the adsorption capacity of catechins and caffeine decreased with an increase in temperature, and that Freundlich and Langmuir models were both suitable for describing the isothermal adsorption of catechins, but not suitable for caffeine. The predicted maximum monolayer adsorption capacity of total catechins by PVPP was 671.77 mg g(-1) at 20 °C, which was significantly higher than that by other reported adsorbents. The thermodynamics analyses indicated that the adsorption of catechins onto PVPP was a spontaneous and exothermic physisorption process, revealing lower temperature was favorable for the adsorption of catechins. Elution tests showed that the desorption rates of catechins and caffeine were higher than 91% and 99% after two elution stages; in detail, almost all of the caffeine could be washed down at the water eluting stage, while catechins could be recovered at the dimethyl sulfoxide/ethanol solution eluting stage. Thus, the PVPP could be used as an excellent alternative adsorbent candidate for separating catechins from crude tea extracts, although some investigations, such as exploring the new eluants with low boiling point and high desorption efficiency, should be conducted furthermore.

Effect of temperature on accumulation of chlorophylls and leaf ultrastructure of low temperature induced albino tea plant

White young shoots from albino tea cultivars have high level of amino acids and are rare and valuable materials for processing green tea. The effects of temperature on leaf colour, accumulation of chlorophylls and leaf ultrastructures of an albino tea cultivar ‘Xiaxueya’ were investigated. The study showed that the shoot albino phenomenon of ‘Xiaoxueya’ was controlled by temperature. The development of chloroplast from etioplast and the accumulation of chlorophylls a and b were blocked and albino shoots were observed at 15°C. However, the albino phenomenon was reversed when the plant was grown at 20°C or above. The authors recommended that the albino tea cultivars should be grown at high altitude or high latitude areas so as to prolong the production season of albino tea shoots.

Suppressive Effects of Tea Catechins on Breast Cancer

Tea leaf (Camellia sinensis) is rich in catechins, which endow tea with various health benefits. There are more than ten catechin compounds in tea, among which epigallocatechingallate (EGCG) is the most abundant. Epidemiological studies on the association between tea consumption and the risk of breast cancer were summarized, and the inhibitory effects of tea catechins on breast cancer, with EGCG as a representative compound, were reviewed in the present paper. The controversial results regarding the role of tea in breast cancer and areas for further study were discussed.

Protective effect of green tea polyphenols against ultraviolet B-induced damage to HaCaT cells

Many deleterious effects on the skin have been associated with the ultraviolet B (UVB) portion of the solar spectrum. The role of green tea polyphenols (GTP) in protecting HaCaT cells against the UVB-induced damages was examined. The promotion effect of low level GTP on cell viability was revealed in a dose-dependent manner. High level GTP had a cytotoxic effect. UVB induced destruction of HaCaT cells, including shedding of cell membrane microvilli, degeneration of nucleus and nucleols and changes of mitochondrial size and internal cristae. GTP alleviated the UVB-induced destructive morphological changes in HaCat cells. It is considered that GTP affords protection against the UVB-induced stress via both interacting with UVB-induced reactive oxygen species and attenuating mitochondrion-mediated apoptosis.

A study on the chemical composition of albino tea cultivars

Summary Tea cultivars ‘Xiaoxueya’ and ‘White leaf No. 1’ have been bred from natural albino mutants of tea plants (Camellia sinensis) and have white tea shoots when the environmental temperature is below 20°–22°C in the early Spring. White tea shoots are used to produce high grades of unfermented tea in China because of their special leaf colour and flavour. The chemical compositions of their shoots were determined by high performance liquid chromatography and compared with ‘Zhenong-113’, a common tea cultivar used for green tea production. Eighteen amino acids and eight catechins were detected in the three cultivars examined, of which theanine was the most abundant amino acid, followed by arginine, glutamic acid, histidine, aspartic acid and threonine. The most abundant catechin was (–) epi-gallocatechin gallate (EGCg), followed by (–) epi-catechin gallate (ECg), and (–) epi-gallocatechin (EGC). Both albino cultivars had significantly higher total amino acid concentrations, but significantly lower concentrations of total catechins and caffeine than ‘Zhenong-113’. The relative compositions of amino acids and catechins differed between both albino mutants and ‘Zhenong-113’. Six out of the 18 amino acids occurred at higher levels in the mutants, four were at lower levels, six showed no difference, and the remaining two were not consistent. ECg and epi-catechin (EC) showed significantly lower levels, but EGC showed higher levels in the mutants, and no differences were observed for EGCg, (–) gallocatechin gallate (GCg) and (–) catechin gallate (Cg), while (–) gallocatechin (GC) and (–) catechin (C) were not consistent.