The roles of catechins and caffeine in cream formation in a semi-fermented tea

The mechanism of cream formation in a semi-fermented tea was investigated by adding caffeine or catechins to the de-creamed tea infusions. The addition of catechins to the clarified infusion could not re-induce cream formation. However, creaming occurred again after replenishing the de-creamed tea infusion with caffeine. It was thought that the ester-form catechins which possessed a galloyl group and a hydroxylphenyl B ring acted like a claw. They could thus entrap and interact with caffeine more effectively through hydrogen bonding and hydrophobic interaction to form a large complex, resulting in creaming. © 1999 Society of Chemical Industry     

Factors affecting the levels of catechins and caffeine in tea beverage: estimated daily intakes and antioxidant activity

Increased public awareness of health benefits of green tea is generally based on the high polyphenol content of tea leaves and the resulting beverage. A number of factors, such as species, season, agronomic condition and age of the leaves, are known to affect the composition of commercial teas. In the present study the effects of factors associated with domestic preparation and analytical methods, such as brewing time, concentration, solvent and type of tea product, on levels of catechins and caffeine, antioxidant activity and estimated daily intakes were investigated. There were large variations in the levels of total catechins: 43 and 117 mg g^?1 dry matter (DM) (brewed for 30 s and 5 min respectively); 72 and 161 mg g^?1 DM (extracted in boiling water and 50% acetonitrile respectively); 72 and 117 mg g^?1 DM (a tea bag and tea leaves respectively). The effects on caffeine content were comparatively smaller. These variations consequently led to considerable variations in estimated daily intakes based on three cups (600 ml), ranging between 538 and 2014 mg g^?1 DM of total catechins and between 103 and 466 mg g^?1 DM of caffeine. The antioxidant activity was highest (26 680 µmol g^?1 DM) for tea leaves brewed for 5 min and lowest (10 110 µmol g^?1 DM) for a tea bag product brewed for 1 min. Copyright © 2005 Society of Chemical Industry     

工夫红茶咖啡碱和5种儿茶素组分近红外快速测定方法的研究

提出一种利用近红外光谱技术无损快速检测工夫红茶咖啡碱(Caffeine)和5种儿茶素(儿茶素(Catechin,C)、表儿茶素(Epicatechin,EC)、表没食子儿茶素(Epigallocatechin,EGC)、表儿茶素没食子酸酯(Epicatechin gallate,ECG)、表没食子儿茶素没食子酸酯(Epigallocatechin gallate,EGCG))组分含量的新方法。实验样品共计240个,手动选择180个样品作为校正级,剩余60个样品作为预测集;利用OPUS7.0软件优化出各模型最佳波数段和最佳预处理方法,平滑点数17,维数1,结合咖啡碱(Caffeine)和5种儿茶素组分C、EC、ECG、EGC、EGCG含量建立预测模型,分析预测模型的预测性能。结果表明:各预测模型预测精准度高,均可用于咖啡碱和5种儿茶素组分C、EC、ECG、EGC、EGCG检测。其中,各模型校正相关系数(Rc)为91.85%~99.49%,校正均方根误差(RMSEC)为0.0187~0.353;预测相关系数(Rp)为97.12%~99.88%,预测均方根误差(RMSEP)为0.00759~0.0773。各模型校正集和预测集均有较高的拟合度,模型预测性能咖啡碱>EGC>EC>ECG>EGCG>C。结论:近红外光谱图结合咖啡碱(Caffeine)和5种儿茶素组分C、EC、ECG、EGC、EGCG含量建立的各预测模型预测性能优,可用于工夫红茶咖啡碱(Caffeine)和5种儿茶素组分C、EC、ECG、EGC、EGCG含量快速无损检测。      

Analysis of caffeine and flavan‐3‐ol composition in the fresh leaf of Camellia sinesis for predicting the quality of the black tea produced in Central and Southern Africa

A parameter of fresh tea leaf that correlates with black tea quality is highly desired. Twenty good and 20 poor quality tea clones were selected from the breeding programme at the Tea Research Foundation (Central Africa) (TRF(CA)). The flavan‐3‐ol profile of fresh tea leaves was analysed by capillary electrophoresis while total theaflavin (TF) content was determined in the black tea manufactured from the same leaves for each clone. The above parameters were correlated with total scores and valuation from two tea tasters with regression analysis. The significance of the differences between the 20 good and 20 poor quality tea clones was determined with the Student's t‐test. The total TF content of the black tea correlated (r = 0.63, P = 0.0001) well with the value of the tea. Of all the parameters determined in the fresh leaves, the highest correlation was obtained with (−)‐epicatechin (EC) (r = 0.65, P = 0.0001). This may facilitate early selection of good quality TRF(CA) clones in the future. © 2000 Society of Chemical Industry     

市售茶饮料中茶多酚、咖啡因以及茶氨酸的含量分析

测定了茶饮料中的茶多酚(Tea Polyphenols,TP)、游离氨基酸总量、表没食子儿茶素没食子酸酯(Epigallocatechi Gallate,EGCG)、咖啡因(Caffeine,CAF)和茶氨酸(L-Theanine,TA)的含量.结果表明:目前市售茶饮料的品质与品牌无关,乌龙茶TP、EGCG和CAF含量最高,乌龙茶和花茶中TP含量完全符合国家标准,绿茶合格率为85.0%,而红茶合格率仅为50.0%.除了两个绿茶饮料样本低于国家标准外,其它样本中的CAF含量全部符合国家标准.     

咖啡碱吸附剂的选取及蒙脱土对绿茶茶汤中咖啡碱的吸附工艺优化

基于咖啡碱可能会引发相关疾病的发生,本实验采用物理吸附方式对茶汤中咖啡碱进行吸附脱除,选取活性炭、蒙脱土和石英砂三种吸附剂对绿茶茶汤进行咖啡碱的吸附实验,选出最佳吸附剂蒙脱土,在响应曲面优化下得到最佳吸附条件:吸附时间1.6 h,茶汤pH在2.07附近,蒙脱土用量为4%,最终体系中咖啡碱含量为0.991%,生物活性物质损失不超过6%,表明在三种吸附剂中蒙脱土是可行和实用的脱除绿茶中咖啡碱的吸附剂,为制备低咖啡碱绿茶速溶茶提供理论依据。     

Mineral and trace metal levels in some cheese collected from Turkey

Concentrations of elements (Fe, Mn, Zn, Cu, Pb, Cr, Ni, Na, K, Ca and Mg) in cheese samples were analyzed using flame and graphite furnace atomic absorption spectrometry after microwave digestion. The order of levels of the elements in the samples was determined to be Na > Ca > K > Mg > Zn > Fe > Pb > Mn > Cr > Ni. The concentration ranges in the samples were found to be 4.1–12.5, 0.28–1.1, 8.8–13.2, 0.10–0.27, 0.14,–1.2, 0.02–0.62, 0.18–0.34, 3957–6558, 305–362, 3473–4556 and 28.9–127 μg/g for iron, manganese, zinc, copper, lead, chromium, nickel, sodium, potassium, calcium and magnesium, respectively. High trace metal and mineral accumulation levels in the samples were found in Van otlu cheese for Fe, Ordu çerkez cheese for Na, Kayseri çömlek cheese for Mn, Pb, Çeçil cheese for Zn, Kars ka?ar cheese for Cu, Cr, Tokat cheese for Ni, Ca and Erzincan tulum cheese for K, Mg, respectively.     

HPLC determination of caffeine in tea,chocolate products and carbonated beverages

Different brands of mate and black tea, chocolate products and carbonated beverages available on the Brazilian market were analysed for caffeine by high-performance liquid chromatography with a UV-vis detector at 254 nm. The column was a reverse phase C18 and the mobile phase consisted of methanol–water (30:70, v/v), acetonitrile–water (10:90, v/v) and methanol–water (25:75, v/v) for tea, chocolate products and soft drinks respectively. Caffeine content ranged from 1.05 to 15.83 mg per cup in mate tea, from 32.21 to 36.23 mg per cup in black tea, from 0.14 to 0.95 mg g⁻¹ in chocolate products from 2.73 to 7.49 mg per can in guaraná-type soft drinks and from 19.81 to 45.89 mg per can in cola soft drinks. These data indicate that the levels of caffeine in Brazilian teas, chocolates and soft drinks are within the ranges reported for similar products in other countries. © 1999 Society of Chemical Industry     

The effect of vacuum packaging on the microbial spoilage and shelf-life of ‚ready-to-use’︁ sliced carrots

The effect of vacuum packaging on the microbial spoilage of ?ready-to-use’? carrot slices and on the effect on shelf-life of the product is reported. The microbial development on vacuum packaged carrots was slower than that of non-vacuum packaged material. The predominant organisms present were Leuconostoc spp. in the vacuum packs as opposed to Erwinia spp. in the aerobic packs. Vacuum packaging of the sliced carrots significantly extended the shelf-life of the product when stored at 4°C from 5 to 8 days.     

Meat panel short paper reading meeting on ‚cooking of meat—art or science?’︁

The following are summaries of papers presented at a meeting of the Meat Panel of the Food Group held on 8 October 1980 at the Society of Chemical Industry, 14 Belgrave Square, London SW1X 8PS. Papers so published are entirely the responsibility of the authors and in no way reflect the views of the Editorial Board of the Journal of the Science of Food and Agriculture.     

Analysis of some selected catechins and caffeine in green tea by high performance liquid chromatography

Green tea seems to have a positive impact on health due to the catechins-found as flavanols. Thus, the present study was aimed to develop a low cost reversed phase high performance liquid chromatographic (HPLC) method for simultaneous determination of flavanol contents, namely catechin (C), epicatechin (EC), epigallocatechin (EGC), epicatechin 3-gallate (ECG) and epigallocatechin 3-gallate (EGCG) and caffeine in 29 commercial green tea samples available in a Saudi Arabian local market. A C-18 reversed-phase column, acetonitrile–trifluoroacetic acid as a mobile phase, coupled with UV detector at 205 nm, was successfully used for precise analysis of the tested analytes in boiled water of digested tea leaves. The average values of N (No. of theoretical plates), HETP (height equivalent of theoretical plates) and R_s (separation factor) (at 10 μg ml⁻¹ of the catechins EC, EGC, EGCG and ECG) were 2.6 × 10³ ± 1.2 × 10³, 1.7 × 10⁻³ ± 4.7 × 10⁻⁴ cm and 1.7 ± 5.53 × 10⁻², respectively. The developed HPLC method demonstrated excellent performance, with low limits of detection (LOD) and quantification (LOQ) of the tested catechins of 0.004–0.05 μg ml⁻¹ and 0.01–0.17 μg ml⁻¹, respectively, and recovery percentages of 96–101%. The influence of infusion time (5–30 min) and temperature on the content of the flavanols was investigated by HPLC. After a 5 min infusion of the tea leaves, the average concentrations of caffeine, catechin, EC, EGC, ECG and EGCG were found to be in the ranges 0.086–2.23, 0.113–2.94, 0.58–10.22, 0.19–24.9, 0.22–13.9 and 1.01–43.3 mg g⁻¹, respectively. The contents of caffeine and catechins followed the sequence: EGCG > EGC > ECG > EC > C > caffeine. The method was applied satisfactorily for the analysis of (+)-catechin, even at trace and ultra trace concentrations of catechins. The method was rapid, accurate, reproducible and ideal for routine analysis.     

A property-activity approach to relating ‚flavour’︁ thresholds in one substrate to their value in a second substrate

The ratios of the logarithms of reciprocals of flavour (combined odour/taste) or odour, thresholds in aqueous and oil media can be significantly linearly related to the octanol/water partition coefficients (as log P) of the compounds considered. The use of this lipophilicity parameter to relate thresholds determined in different media may allow the estimation of thresholds in oil media, or oil-based food products, from the thresholds in water.     

Presence of two forms of methylated (–)‐epigallocatechin‐3‐gallate in green tea

Crude catechins extract from Chinese green tea were fractionated using Sephadex LH‐20 column chromatography. The fraction containing (–)‐epigallocatechin‐3‐gallate (EGCG) was then subjected to a semipreparative high‐performance liquid chromatography (HPLC). Using a mobile phase of water : dimethyl formamide : methanol : acetic acid (157 : 49 : 2 : 1 v/v/v/v( the mixture of two methylated catechins was separated and isolated. According to mass spectrometry (MS) and nuclear magnetic resonance (¹H‐NMR) date, these compounds were identified as (–)‐epigallocatechin‐3‐(3‐O‐methylgallate) and (–)‐epigallocatechin‐3‐(4‐O‐methylgallate).     

Diversity among various forms of catechins and its synthesizing enzyme (phenylalanine ammonia lyase) in relation to quality of black tea (Camellia spp.)

BACKGROUND: Quality of tea depends on the cultivar and climatic conditions. Biochemical pathways within the plant and climatic factors can result in noticeable changes in chemical composition, which determine the quality of tea. Black tea quality attributes are influenced by various forms of catechins, namely gallated, non‐gallated, dihydroxylated and trihydroxylated catechins and their ratios. Hence the variations in grouped catechins and their synthesizing enzyme in relation to quality of south Indian black tea grown in different seasons and different cultivars were studied. RESULTS: Gallated, non‐gallated, dihydroxylated, trihydroxylated catechins and catechin index were significantly higher in crop shoots harvested during summer. A significant and wide diversity in various forms of catechins was noticed among the cultivars tested. Among the cultivars, UPASI‐3 registered the higher amount of various forms of catechins and activity of phenylalanine ammonia lyase (PAL), followed by UPASI‐9 and UPASI‐17 respectively, while the lowest amount was exhibited by ‘Assam’ seedlings and TRI‐2043. CONCLUSION: Overall quality as evaluated by tea tasters was positively correlated to the cultivars and seasons tested. This positive correlation can be attributed to higher levels of grouped catechins and PAL activity. Thus the contents of various forms of catechins could be the most important quality parameter of the south Indian black teas. Copyright © 2010 Society of Chemical Industry     

Nutritional quality of acid-precipitated protein concentrate from the Nigerian ‚red skin’︁ groundnut (Arachis hypogaea L.)

Groundnut protein concentrate (GPC) prepared by isoelectric centrifuging at pH 4 was subjected to treatment with 0–12M hydrogen peroxide in the same manner as is used to destroy aflatoxins. The protein solubility, in-vitro digestibility, amino acid composition and enzymic protein efficiency ratio (E-PER) were compared with those of untreated concentrate. The nitrogen solubilities were markedly lower at acidic pH but comparable to values obtained from untreated samples at alkaline pH; the digestibilities ranged from 71.4 to 92.1% in treated samples and from 73.7 to 98.0% in untreated samples. There was a marked reduction in the content of threonine, proline, cystine, methionine and tryptophan, which was reflected in the lower E-PER value for the treated samples. Despite these changes, peroxide-treated GPC is a potentially useful supplement to many cereal-based Nigerian weaning foods and breakfast preparations.     

Effect of root zone pH and form and concentration of nitrogen on accumulation of quality‐related components in green tea

Green tea quality is greatly influenced by concentrations of free amino acids, polyphenols (mainly catechins) and caffeine. The present study investigated the principal relationship between selected nutritional factors (form and concentration of N supply, root zone pH) and accumulation of these quality‐related components of tea (Camellia sinensis (L.)) plants. Tea plants were hydroponically cultured with NH , NO and NH NO at pH 4.0, 5.0 and 6.0 in one experiment and supplied with varying N concentrations (0.75, 2.0 and 4.5 mmol L^?1, NH /NO^?₃ = 3:1) in another experiment. Concentrations of free amino acids were considerably higher in NH ‐ than in NO ‐fed plants. This was attributed to the much greater absorption of NH compared with NO . Furthermore, the relative allocation of absorbed N to free amino acids, particularly theanine and glutamine, was substantially increased by NH nutrition, suggesting that NH was more readily assimilated than NO into theanine. The concentration of caffeine was increased in NH ‐ and (NH NO )‐supplied plants, whereas concentrations of catechins were reduced in (NH NO )‐fed plants. Root zone pH did not influence concentrations of most free amino acids in young shoots, with the exception of theanine, which increased at low pH (4.0) irrespective of N form; this likely stemmed from an accumulation effect, as growth decreased more strongly than N absorption. Raising the N supply increased plant N allocation to free amino acids. The increase was most striking for arginine, while theanine was only marginally affected. This may have adverse consequences for green tea quality, as less favourable taste characteristics have been attributed to arginine. Copyright © 2007 Society of Chemical Industry     

Changes during ensilage in fermentation products,tea catechins,antioxidative activity and in vitro gas production of green tea waste stored with or without dried beet pulp

Wet green tea waste (GTW) was ensiled in laboratory silos with or without dried beet pulp at a ratio of 2:1 on a fresh weight basis. The silos were opened at 15, 30 and 60 days after anaerobic storage; fermentation products, tea catechins, antioxidative activity and in vitro gas production were determined. Acetic acid prevailed over the fermentation and the pH declined to below 4.2 when wet GTW was ensiled alone. Addition of dried beet pulp greatly enhanced lactic acid production and the pH further decreased to below 3.8 with no butyric acid being detected. Approximately 90% and 80% of (?)‐epicatechin gallate and (?)‐epigallocatechin gallate, respectively, were degraded in silage prepared from wet GTW alone, while the degradation was ameliorated in mixed silage to about 55% and 70%, respectively. Antioxidative activity was not markedly altered by ensiling and 70–80% of the initial activity was detected after 60 days. Changes were small in (?)‐epigallocatechin, caffeine and total phenols with or without mixing with dried beet pulp. In vitro gas production was similar between materials and their silages, indicating that reduction of tea catechins would not elicit an improvement in digestibility. It is concluded that wet GTW can be ensiled successfully without bacterial inoculants when mixed with other materials containing certain sugars. Ensiling may degrade part of the components of tea catechins, while not affecting total phenols, antioxidative activity and digestibility of wet GTW. Copyright © 2007 Society of Chemical Industry     

用荷移光度新方法测定茶叶及茶饮料中咖啡因的含量

用分光光度法研究了咖啡因作为电子给予体与电子接受体四氯对苯醌的荷移反应。确定了反应及测定的条件为:在硼砂与NaOH构成的缓冲溶液中,咖啡因分别与四氯对苯醌混匀于(20±1)℃的水浴中恒温20 min,可形成1:2的稳定荷移络合物,其可见光区内的最大吸收波长为λ_(max)=536 nm,表观摩尔吸光系数ε= 1.684×10~4L/mol·cm,最低检测限为1.9μg/mL,在1×10~(-5)～3.0×10~(-4)mol/L内符合比耳定律,线性方程为△A=1.485 6×10~4-0.0406(r=0.997)。该法对市售的茶叶和茶饮料中咖啡因含量测定的结果与GB/T 16344—1996法一致,回收率在99.1%～102.8%,RSD为2.0%～3.3%,茶叶经热水漫泡处理和茶饮料的直接测定与CHCl_3萃取处理的效果一样,茶叶和茶饮料中共存的其他组分不干扰测定。     

Analysis of the theaflavin composition in black tea (Camellia sinensis) for predicting the quality of tea produced in Central and Southern Africa

A parameter of black tea that correlates with quality is highly desired. Twenty good and 20 poor quality tea clones were selected from the breeding programme at the Tea Research Foundation (Central Africa) (TRF(CA)). The theaflavin (TF) composition of the black tea manufactured from each clone was analysed by capillary electrophoresis and correlated with total scores and valuation from two tea tasters with regression analysis. The significance of the differences between the 20 good and 20 poor quality tea clones was determined with the Student t‐test and the distribution‐free Kruskal–Wallis test. The sum of the TFs of the black tea correlated well (r = 0.785, P = 0.0002) with the value of the tea. Of the individual TFs determined in the black tea, the highest correlation was obtained with TF‐3′‐monogallate (TF‐B) (r = 0.788, P = 0.0016), TF‐3‐monogallate (TF‐A) (r = 0.741, P = 0.0004) and free TF (TF‐f) (r = 0.705, P = 0.0002). TF‐B (m = 24.90) followed by TF‐A (m = 12.48) showed the steepest slopes against value, making them good indicators for value. The TF‐digallate (TF‐dg) content did not show significant correlation with value (r = 0.316, P = 0.358). The individual TF content thus can be used for optimising the black tea manufacturing process in Central and Southern Africa. © 2002 Society of Chemical Industry