Kinetics and equilibria of tea infusion—Part 6: The effects of salts and of pH on the concentrations and partition constants of theaflavins and caffeine in Kapchorua Pekoe fannings

The concentrations of theaflavins and of caffeine in sieved Kapchorua Pekoe Fannings (600–710 μm) have been determined at 80°C with a range of aqueous salt and buffer solutions of ionic strength 0·11 mol dm⁻³ and of pH 1·9 to 8·3. The caffeine concentration in the infusions and in the leaf, and its partition constant between swollen leaf and solution, was little affected by the presence of electrolytes or pH changes. The concentration of theaflavins in the infusions was not changed by the addition of salts but was considerably greater in acid media and also, temporarily, in borate buffers. The acid effect was corroborated by experiments with a Ceylon Broken Orange Pekoe blend. The most significant finding was that the concentration of theaflavins in the Kapchorua leaf rose markedly with falling pH while its partition constant decreased. These results show that hydrogen ions liberate extra theaflavin by breaking down the leaf structure and/or the bonding of some theaflavin within the leaf. The effect has significant commercial implications since the market price of tea leaf correlates with its theaflavin content.     

Evaluation of the taste contribution of theaflavins in black tea infusions using the taste activity concept

The contribution of theaflavins to the astringent taste of black tea infusions has been investigated. The major benzotropolons theaflavin, theaflavin-3-gallate, theaflavin-3-gallate, theaflavin-3,3-digallate, and theaflavic acid were synthetically prepared by enzymatic oxidation of binary mixtures of the corresponding flavan-3-ols, purified by high-speed countercurrent chromatography, and then sensorially evaluated by means of a comparative duo test. The sensory analysis revealed that the theaflavins imparted a mouth-coating, astringent, and long-lasting oral sensation at the very back of the throat, and demonstrated the theaflavins to have by far lower oral thresholds than the astringent catechins; for example, the threshold concentration of theaflavin (0.016 mmol/L) is by a factor of 33 and 58 lower than those of its precursors epigallocatechin and epicatechin, respectively. In order to study the importance of these theaflavins as contributors to tea astringency, these benzotropolons were quantified in tea infusions and taste activity values were calculated from the quotient of their concentration in tea and their taste detection thresholds. Relating the taste activity values of the individual theaflavins to the overall astringency of the teas revealed that the theaflavins accounted for less than 0.1% of the overall astringency of the teas investigated. In consequence, the theaflavin concentration seems not to be a suitable measure for taste quality of tea infusions.     

Catechins depletion patterns in relation to theaflavin and thearubigins formation

The determination of the depletion pattern of catechins in black tea processing is important in achieving optimum tea quality. This study investigated catechins (unoxidised di- and trihydroxylated) depletion patterns in relation to theaflavin and thearubigin formation. It was during the process of green leaf fermentation at selected temperature and time combinations. The tea leaves were obtained from three clones (6/8, 303/577 and 311/287) within the Tea Research Foundation of Kenya. The results were showed that unequal depletion rates of di- and trihydroxylated catechins led to a decline in total theaflavin and an increase in thearubigins levels. An equitable decline in both groups of catechins corresponded to a subsequent rise in theaflavins content. The decline in the catechins levels was much faster at higher temperatures resulting in a shorter fermentation time to achieve a peak of the theaflavins content. Clone 311/287 had the highest mean theaflavins content (26.99 μmol/g) and the least mean percent thearubigins (15.02%) level. Theaflavins content correlated positively with liquor brightness determined by a spectrophotometer and tea tasters (r = 0.7221, p < .0001). The thearubigins content was however found to relate negatively with liquor brightness. It was concluded that the experimental conditions tested form a good basis for clonal specific processing conditions that can be utilised in manufacturing quality black tea.     

The relationship between some chemical parameters and sensory evaluations for plain black tea (Camellia sinensis) produced in Kenya and comparison with similar teas from Malawi and South Africa

Reliable and accurately measurable chemical parameters that can be used to estimate black tea quality are desirable in trade, research and breeding programmes. Using plain Kenyan black tea from 11 cultivars, which gave some significant differences in their plain black tea quality parameters, the individual theaflavins composition, total theaflavins, thearubigins, theaflavin digallate equivalent, total colour and brightness were determined. The parameters were regressed against sensory evaluation scores of two tasters A and B. The theaflavin digallate equivalent (TDE) showed the strongest relationship (r = 0.71 (P ? 0.01) and r = 0.80 (P ? 0.001)) for A and B′, respectively. The simple (non gallated) theaflavin and thearubigins did not show significant relationships with sensory evaluation. Of the liquor characteristics, there were significant relationships between liquor brightness and sensory evaluation by A and B (r = 0.58 (P ? 0.06) and r = 0.59 (P ? 0.05)), respectively. In consequence, TDE and brightness can be used in tea breeding programmes as quality indicators or to estimate plain black tea quality potential in the tea trade. Optimising their levels can also help to produce good quality Kenyan black teas during processing. Comparison of these results with work published earlier indicates that, of the individual theaflavins, theaflavin-3,3′-digallate correlates best with tea taster scores for the 11 Kenyan cultivars, whereas the simple theaflavin correlates best with tea tasters’ scores for 40 Malawian cultivars. However, the derived parameter, TDE correlates very well with tea tasters’ scores for all of the above cultivars.     

The changes in black tea quality due to variations of plucking standard and fermentation time

Catechin levels in green leaf, total theaflavins, brightness, thearubigins, colour, flavour index and sensory evaluation decrease with coarse plucking standard in clone 6/8. The sum of Group I volatile flavour compounds and C₆ aldehydes and alcohols, in particular, increases with coarse plucking standard. The sum of Group II did not follow a particular pattern, but flavour index decreased with coarse plucking standards. The decrease in total theaflavin levels was due to the decrease in all the individual theaflavins. Although all the individual theaflavin levels decreased with coarse plucking standards, the decrease was greater in galloylated theaflavins, especially in theaflavin digallate, compared with simple theaflavin. Short fermentation times produced black teas with higher brightness and flavour index, but lower theaflavins, thearubigins and colour, irrespective of plucking standard. Total theaflavins reached a maximum after 90 min of fermentation, irrespective of the plucking standard, whereas ungalloylated theaflavin levels decreased with extended fermentation duration at all plucking standards, theaflavin-3-gallate and theaflavin-3, 3’-digallate levels increased, resulting in the increase in theaflavin digallate equivalent. Brightness and flavour index decreased while thearubigins, colour, and Groups I and II volatile flavour compound levels increased with long fermentation.     

氧气对茶多酚化学氧化合成茶黄素的影响

研究了O2对茶多酚化学氧化(碱性氧化和酸性氧化)形成茶黄素类物质的影响。结果表明:在接近真空、露置空气和通氧等3种不同O2含量的条件下,茶多酚碱性氧化和酸性氧化均可得到茶黄素类物质,其含量随着2种反应体系中O2含量的增加而增加,且化学氧化中儿茶素消耗的主体是EGCG、EGC、C、EC,说明O2是茶多酚化学氧化形成茶黄素的一个重要影响因素,而相关研究报道却极少涉及到关于O2在茶多酚化学氧化合成茶黄素过程所发挥的作用;另外,比较茶多酚碱性氧化法和酸性氧化法形成茶黄素的情况,前者比后者得到更多茶黄素类物质。文中还考察了O2对茶黄素化学氧化形成的影响。     

高速逆流色谱分离茶黄素条件的优化

优化高速逆流色谱分离4 种茶黄素的方法。两相溶剂系统为正己烷- 乙酸乙酯- 甲醇- 水- 冰醋酸(1:5:1:5:0.25,V/V),固定相为体系的上相,下相为流动相,流速为2ml/min,仪器转速700r/min,进样量30mg。从茶黄素复合物中分离纯化得到茶黄素、茶黄素-3- 没食子酸酯、茶黄素-3＇- 没食子酸酯和茶黄素-3, 3＇- 双没食子酸酯,尤其使得两种酯溶性茶黄素(茶黄素-3- 没食子酸酯、茶黄素-3＇- 没食子酸酯)达到较好的分离。     

Polyphenols Extracted from Black Tea (Camellia sinensis) Residue by Hot‐Compressed Water and Their Inhibitory Effect on Pancreatic Lipase in vitro

Abstract: Polyphenols, retained in black tea wastes following the commercial production of tea beverages, represent an underutilized resource. The purpose of this study was to investigate the potential use of hot‐compressed water (HCW) for the extraction of pancreatic lipase‐inhibiting polyphenols from black tea residues. Black tea residues were treated with HCW at 10 °C intervals, from 100 to 200 °C. The resulting extracts were analyzed using high‐performance liquid chromatography‐mass spectrometry and assayed to determine their inhibitory effect on pancreatic lipase activity in vitro. Four theaflavins (TF), 5 catechins, 2 quercetin glycosides, quinic acid, gallic acid, and caffeine were identified. The total polyphenol content of extracts increased with increasing temperature but lipase inhibitors (TF, theaflavin 3‐O‐gallate, theaflavin 3′‐O‐gallate, theaflavin 3,3′‐O‐gallate, epigallocatechin gallate, and epicatechin gallate) decreased over 150 °C. All extracts inhibited pancreatic lipase but extracts obtained at 100 to 140 °C showed the greatest lipase inhibition (IC₅₀s of 0.9 to 1.3 μg/mL), consistent with the optimal extraction of TFs and catechins except catechin by HCW between 130 and 150 °C. HCW can be used to extract pancreatic lipase‐inhibiting polyphenols from black tea waste. These extracts have potential uses, as dietary supplements and medications, for the prevention and treatment of obesity. Practical Application: Active forms of lipase inhibitors can be recovered from black tea residues. They could be used as dietary supplements or medications.     

青砖茶加工过程品质成分变化研究

目的研究青砖茶加工过程中各化学品质成分含量的变化,为青砖茶风味品质形成提供理论依据。方法以青砖茶发酵前、发酵后及成品为材料,比较分析样品水分、水浸出物、游离氨基酸、咖啡碱、茶多酚、儿茶素组分、茶黄素组分、粗纤维、黄酮、可溶性糖、可溶性果胶等含量变化。结果青砖茶加工过程中,水分含量基本不变,控制在9%左右;纤维素含量呈现上升趋势,成品达到(21.29±0.78)%;水浸出物、可溶性总糖、儿茶素、茶黄素-3'-没食子酸酯、茶黄素总量呈现下降趋势;黄酮含量总体较为稳定,为1.40%~1.83%;茶黄素-3,3'-双没食子酸酯基本稳定在1 mg/g左右;咖啡碱含量发酵后显著低于发酵前;氨基酸、茶多酚、表儿茶素、表儿茶素没食子酸酯、表没食子儿茶素、表没食子儿茶素没食子酸酯、儿茶素总量、茶黄素、茶黄素-3'-没食子酸酯、水溶性果胶均呈现下降后上升,但成品含量低于发酵前原料含量的趋势。结论青砖茶加工过程中不同生化成分变化趋势存在差异,成品与原料存在较大差异,具有粗涩味作用的成分含量降低,各成分间含量更加协调,为青砖茶醇和风味品质形成奠定基础。     

不同冷冻和摇青工艺的红茶品质比较分析

该研究以传统加工的红茶为对照，分析了萎凋前冷冻处理及该处理与萎凋后一次、两次、三次摇青组合处理等新工艺对茶叶品质形成的影响，明确了最佳的工艺处理条件。结果表明，与对照相比，新工艺均可显著增加茶叶没食子酸、茶多酚、茶黄素、黄酮苷等含量（P<0.05），同时，冷冻处理会显著降低可溶性糖含量（P<0.05）（下降10.73%），冷冻和摇青组合处理可显著降低茶褐素含量（P<0.05）（平均下降6.77%）；与冷冻处理相比，冷冻和摇青组合工艺处理可显著降低茶多酚含量（P<0.05）（平均下降3.55%），并显著增加茶黄素含量（P<0.05）（平均增加18.06%）。各处理中以冷冻和两次摇青组合工艺处理的茶叶同时具有相对较高的氨基酸、茶黄素、顺-己酸-3-己烯酯，以及相对较低的没食子酸、儿茶素、黄酮苷、茶褐素、3-辛烯-2-酮，所制红茶呈现橙黄明亮、甜香、甜醇等色香味兼具的品质，感官总分为91.30，分别较对照和冷冻处理高出了2.40、2.60分。综上可知，冷冻和两次摇青的组合处理为最佳新工艺。     

不同产地扁形绿茶的品质成分差异分析

目的：本研究旨在建立同时分析茶叶中4种表儿茶素（表儿茶素、表儿茶素没食子酸酯、表没食子儿茶素和表没食子儿茶素没食子酸酯）及其氧化二聚体（4种茶黄素（Theaflavins,TFs）：茶黄素、茶黄素双没食子酸酯、茶黄素-3-没食子酸酯和茶黄素-3’-没食子酸酯）、3种聚酯型儿茶素（Theasinensins,TSs）（TSA、TSB和TSC）、没食子酸和咖啡碱的高效液相色谱（High performance liquid chromatography,HPLC）方法。方法：首先利用化学合成的方法制备TSA、TSB和TSC;然后参照文献对HPLC流动相做适当调整和对梯度洗脱条件进行优化,色谱柱为Cosmosil 5C₁₈-AR-Ⅱ色谱柱（250 mm×4.6 mm,5 m）,流动相为纯水（A）、50 mmol/L磷酸（B）和乙腈（C）,检测波长为280 nm,流速为0.8 mL/min,柱温为30 ℃,进样量为20 L;最后根据建立的HPLC方法对绿茶、乌龙茶、红茶和黑茶中的上述13种物质含量进行测定。结果：在最优梯度洗脱条件下4种表儿茶素、4种TFs、3种TSs、没食子酸及咖啡碱可在66 min内得到较好地分离,同时各物质在0.01~1.00 mg/mL的质量浓度范围内与其峰面积的线性关系良好（R²均在0.9904~0.9966范围内）,重复性相对标准偏差（The relative standard of deviation,RSD）为1.034%~4.008%,精密度RSD为1.882%~4.835%,稳定性RSD为0.349%~3.994%,三种浓度的加标回收率在90.106%~107.331%之间且RSD<3.268%。此外,上述13种物质含量在不同茶叶样本间存在显著差异,且所有检测值均在标准曲线有效测定范围内。结论：本方法操作简单高效、结果准确可靠,可用于茶叶中表儿茶素、茶黄素、聚酯型儿茶素、没食子酸和咖啡碱的同时分析。     

ANTIOXIDANT PROPERTIES OF POLYPHENOLS EXTRACTED FROM GREEN AND BLACK TEAS

The catechins, including epicatechin gallate (ECG), epigallocatechin (EGC), and epigallocatechin gallate (EGCG), and the theaflavins, including theaflavin (TF), theaflavin monogallate (TF-1), and theaflavin digallate (TF-2), were extracted from green tea and black tea, respectively. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging ability, superoxide-scavenging efficiency, and lipid oxidation-inhibition ability of the pure compounds listed above as well as epicatechin (EC), carnosol, carnosic acid, and butylated hydroxytoluene (BHT) were investigated.
The DPPH radical-scavenging ability of the catechins was EGCG > ECG > EGC > EC and of the theaflavins was TF-2 > TF-1 > TF. EGCG, ECG, EGC, TF-2, TF-1, and TF showed higher DPPH radical- and superoxide-scavenging abilities than carnosol, carnosic acid, and BHT. EGCG, ECG, EGC, carnosol, and carnosic acid showed higher lipid oxidation-inhibition activity, as measured by the Rancimat method, than BHT and theaflavins.     

Preventive effects of black tea theaflavins against mouse type IV allergy

BACKGROUND: Tea (Camellia sinensis L.), one of the most popular beverages, contains various beneficial constituents. We investigated the preventive effects of black tea theaflavins, theaflavin‐3‐gallate (3‐TF) and theaflavin‐3,3′‐digallate (TFDG), on oxazolone‐induced type IV allergy in male ICR mice. RESULTS: Percutaneous administration of both 3‐TF and TFDG at 0.2 mg ear^?1 showed significant preventive effects against mouse type IV allergy. Oral administration of these agents at 50 mg kg^?1 body weight also showed significant preventive effects against mouse type IV allergy. Oral administration of 3‐TF and TFDG at a dose of 50 mg kg^?1 body weight prevented the increases in levels of some proinflammatory cytokines, interleukin‐12 (IL‐12), interferon‐gamma (IFN‐γ), and tumour necrosis factor‐alpha (TNF‐α), in the sera and/or ears of mice with type IV allergy. Lowering of serum antioxidant activity in mice with allergic symptoms was also prevented by oral administration of these theaflavins at a dose of 50 mg kg^?1 body weight. The anti‐allergic mechanisms of action of theaflavins involve inhibition of the fluctuations of cytokines and maintenance of antioxidant status in allergic mice. CONCLUSION: These results suggest that the theaflavins as well as catechins contribute to the anti‐allergic effects of black tea. Copyright © 2010 Society of Chemical Industry     

Chemical assessment of quality in tea and its relation to the market over an extended period

The relationship between auction selling price and content of total theaflavins and total colour was investigated for teas sold on 25 occasions between June 1971 and December 1973. The extent to which price depended upon theaflavins and total colour varied according to the geographical area of origin of the tea and to the time of sale. While theaflavin content was generally the best explanation of price, total colour measurement added to the explanation on many occasions, particularly with teas from North East India. Possible ways in which seasonal market supply factors might influence the relationship are discussed.     

Phenolic compounds in coffee pulp: Quantitative determination by HPLC

The content of phenolic compounds tentatively identified by HPLC in fresh coffee pulp gives an average composition in the 12 cultivars studied as follows: chlorogenic acid (5-caffeoylquinic acid), 42·2%; epicatechin, 21·6%; isochlorogenic acid I, 5·7%; isochlorogenic acid II, 19·3%; isochlorogenic acid III, 4·4%; catechin, 2·2%; rutin, 2·1%; protocatechuic acid, 1·6%; and ferulic acid, 1·0%. When the percentages of chlorogenic and isochlorogenic acids are added to the corresponding one of epicatechin for each cultivar, it is found that they make up between 92·0% and 98·4% of the total of identified phenolic compounds. Qualitative or quantitative differences were not detected between cultivars of coffee plants resistant and susceptible to coffee leaf rust.     

不同品种英德红茶的品质比较分析

本研究以四种常见英德茶叶品种(A、B、C、D)为研究对象,通过检测茶叶中茶多酚、氨基酸、水溶性糖、茶黄素、抗氧化活性等营养指标以及茶叶质量感官评定,对四种茶叶之间的品质进行对比分析.结果表明:四种红茶茶多酚含量在14.53％～21.98％,水浸出物含量在29.57％～38.56％,氨基酸含量在2.85％～3.04％,茶...     

Time-related changes in volatile compounds of lean tissue during processing of French dry-cured ham

The Biceps femoris muscles from 50 hams were used in the study. Ten samples were taken for analysis on the day after slaughter. Forty hams were drycured and taken for analysis by groups of 10 at days 74, 81, 179 and 273 after the beginning of processing. Volatile compounds were extracted from the middle part of the Biceps femoris muscle by dynamic headspace extraction, then analysed by gas chromatography and mass spectrometry. More than 100 peaks were detected, among which 74 were identified and 52 were quantified. Most identified compounds originated from either lipid oxidation or amino acid degradation. The total quantity of extracted compounds increased dramatically between day 0 and day 74. Propanone was by far the most abundant compound, followed by the other ketones, alcohols and aromatic hydrocarbons (66·5, 9·9, 9·2 and 8·4% of the total chromatogram area, respectively, at the end of processing). The levels of individual compounds varied greatly during processing. There was some evidence of independence between the reactions producing volatile compounds from lipids and those involving amino acids.     

Oxidative cascade reactions yielding polyhydroxy-theaflavins and theacitrins in the formation of black tea thearubigins: evidence by tandem LC-MS

LC-MS(n) and direct infusion-MS(n) have been applied for the first time to the characterisation of crude thearubigins isolated from black tea. The data generated have been used to test two hypotheses of thearubigin structure: (i) that a significant fraction of the thearubigins consist of polyhydroxylated derivatives of the better-known catechin dimers (theaflavins, theaflavin mono- and di-gallates, theacitrins) in redox equilibrium with their associated quinones; and (ii) that a significant fraction of the thearubigins consist of dicarboxylic acids generated by oxidative cleavage of aromatic diols. The data were consistent with the polyhydroxylation hypothesis and did not support the dicarboxylic acid hypothesis. Evidence is presented for the presence in crude thearubigins of at least 29 hydroxylated theaflavins (with between one and six oxygen insertions), at least 12 theaflavin mono-gallates (with between one and six oxygen insertions), at least nine theaflavin di-gallates (with between one and four oxygen insertions), and at least ten theacitrin mono-gallates (with between one and four oxygen insertions). Evidence is also presented for at least ten mono- or di-quinone forms of the parent compounds and hydroxylated derivatives in each of these homologous series. A general method for the analysis of complex mixtures by tandem LC-MS is furthermore introduced and established.     

不同茶树品种悬浮发酵对茶黄素形成的影响

以同一嫩度的英红9号、福鼎大白、金观音、槠叶齐4 个差异性较大品种的鲜叶为原料进行悬浮发酵实验,开展茶树品种、酶源类型（多酚氧化酶（polyphenol oxidase,PPO）、过氧化物酶（peroxidase,POD）活性等）、儿茶素组分（含量、配比等）对茶黄素形成影响的研究,结果表明：PPO活性/POD活性比值以福鼎大白最高,英红9号和金观音次之;简单儿茶素总量（total simple catechin,TSC）和酯型儿茶素总量（total ester-type catechin,TETC）均以英红9号最高,福鼎大白和金观音次之,槠叶齐最低;各儿茶素组分除没食子儿茶素没食子酸酯和儿茶素没食子酸酯外均呈前期迅速下降、后期平稳的趋势,儿茶素剧烈消耗期在发酵前30?min;茶黄素组分形成量均呈先升后降的趋势,峰值点在发酵15?min和30?min,不同品种不同茶黄素组分峰值时间和高度不同;整体上,以最高儿茶素底物含量和第2高PPO活性/POD活性比值的英红9号品种茶黄素的形成量显著最多,最高PPO活性的福鼎大白和金观音品种可最快形成茶黄素,但较高活性的POD和较低含量的儿茶素,导致茶黄素的形成量较低,而具有最低PPO活性/POD活性比值和最低含量的儿茶素底物的槠叶齐品种形成茶黄素的能力最差。即PPO活性/POD活性比值越大,儿茶素底物含量越大,TETC/TSC比值越大,形成茶黄素的能力越强。