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     

Phytate and Zinc Contents of Coffees, Cocoas, and Teas

Several samples of coffee, both instant and percolated, hot cocoa mixes, and teas, both instant and brewed, were analyzed for phytate and zinc. Phytate:zinc molar ratios were calculated. An estimation of the phytate contribution from the beverages to the total diet presented. Depending upon the source selected and the strength and quantity of the beverage consumed, there is concern that a high take of these beverages may exacerbate an already marginal zinc status.     

Caffeine Content of Retail Market Coffee in Portugal

How much caffeine does one ingest when drinking a simple cup of coffee in Portugal? The study presented herein tried to answer this question through the assessment of caffeine content of commercially available espresso coffee samples, both caffeinated and decaffeinated, using a high-performance liquid chromatography assay. Caffeine was rapidly separated from the sample matrix using a RP-18 column (250?×?4 mm i.d., 5 μm). The flow rate was 1.0 mL/min and the mobile phase consisted of water acidified with 5% of orthophosphoric acid/methanol (35:65, v/v). Caffeine was detected directly at 273 nm. The assay was validated for linearity, lower limit of quantification and limit of detection, precision, accuracy, and stability. Seventeen different brands of caffeinated coffee and six of decaffeinated coffee were analyzed. As for capsule coffee, eight caffeinated and two decaffeinated blends were analyzed. The caffeine content of caffeinated coffee varied from 53.8?±?5.9 to 141.3?±?5.3 mg/cup, whereas for caffeinated capsule coffee caffeine concentrations ranged from 45.0?±?5.3 to 60.8?±?6.2 mg/cup. As for decaffeinated coffee, caffeine concentrations ranged from 0.96?±?0.04 to 3.9?±?0.1 mg/cup and for decaffeinated capsule coffee from 0.93?±?0.04 to 1.2?±?0.1 mg/cup.     

The effect of instant green tea on the foaming and rheological properties of egg albumen proteins

The effects of three varieties of instant green tea (from China, Japan and Kenya) on the foaming and thermal properties of 1% (w/v) egg albumen and the gelation properties of 5 and 15% (w/v) egg albumen were investigated. All varieties produced similar effects on the foaming and gelation properties of egg albumen, but to different extents depending on the tea constituents. Mixtures of 1% (w/v) egg albumen and 0.25–0.4% (w/v) instant green teas in distilled water showed the greatest foam expansion (800–1140%) and foam stability (97–100%) at 10 min after whipping compared with 1% (w/v) egg albumen alone (226% for foam expansion and 34% for foam stability). Addition of instant green teas at levels above 0.5% (w/v) decreased foam expansion and stability. Small‐deformation rheology of mixtures of 5% (w/v) egg albumen and 1 or 2% (w/v) instant green teas showed an initial increase in elastic modulus (G′) and viscous modulus (G″) followed by a small, broad peak, indicating that the binding of tea constituents (polyphenols) with proteins may be reversible between 20 and 54 °C; this peak was not seen for 5% (w/v) egg albumen on its own. Large‐deformation rheological tests also indicated increased strength of mixed egg albumen/green tea gels with increasing levels of instant green teas. Differential scanning calorimetry thermograms showed that for the same instant green tea a higher concentration decreased the onset and peak (T_m) temperatures and enthalpy change values of all egg albumen protein peaks. Copyright © 2007 Society of Chemical Industry     

Method Validation for Cafestol and Kahweol Quantification in Coffee Brews by HPLC-DAD

Cafestol and kahweol are two diterpenes exclusively found in coffee. Negative effects on health, like the increase in total lipid blood levels as well as positive effects like carcinogenic protective and antioxidant activity, have been reported for these two compounds. A simple and expeditious method for the quantification of total cafestol and kahweol levels in coffee brews by high-performance liquid chromatography with diode array detection was developed and validated. Esterified diterpenes were hydrolysed and resulting diterpene alcohols extracted with diethyl ether. For cafestol limit of detection was 0.01 mg L^?1 and limit of quatification was 0.04 mg L^?1. Coefficient of variation for cafestol ranged between 0.2 and 2.8 % for repeatability and between 1.4 and 15.3 % for intermediate precision. Average recoveries of cafestol-spiked coffee samples were from 96 to 110 %. Kahweol was quantified using cafestol calibration data and corrected by an appropriate conversion factor. Different kinds of coffee brews were analysed. Cafestol levels ranged from 0.04 to 0.80 mg/cup and for kahweol levels were between 0.01 and 0.40 mg/cup. Highest levels of diterpenes per cup were present in espresso coffee, while the lowest were found in filter coffee and instant coffee.     

Determination of purine alkaloids and trigonelline in instant coffee and other beverages using high performance liquid chromatography

A simple, rapid high performance liquid chromatography method is reported for the simultaneous analysis of trigonelline and caffeine (1,3,7-trimethylxanthine) in coffee, and theobromine (3,7-dimethylxanthine) and caffeine in samples of cocoa, drinking chocolate, tea and cola. Chromatography was carried out on Spherisorb-ODS columns with gradient elution. The eluate was monitored at 272 nm with an ultraviolet spectrophotometer and quantification was achieved with external standards. Results for different brands of instant coffees, one decaffeinated coffee, and for samples of cocoa, drinking chocolate, tea and cola are reported.     

Instant food products as a source of silicon

Silicon is a trace element for humans, and is absorbed from food in the form of orthosilicic acid. Instant food products are part of a constantly growing market of convenience foods, which have not been evaluated yet as sources of silicon. In this study the total and soluble silicon contents in different instant food products were determined by using graphite furnace atomic absorption spectrometry (GF-AAS). A selection of instant products commercially available in Wroclaw were analyzed: soups, main courses, coffee drinks, jellies and puddings. Total silicon contents in soups, main courses and coffee drinks ranged widely and reached the values: 0.10–30.20, 0.63–37.91 and 0.21–13.37 mg/serving, respectively. These products contained 0.05–1.26 mg of soluble silicon per serving. The total silicon content in jellies and puddings did not exceed 0.36 mg and 2.42 mg/serving, respectively. Among the analyzed desserts the highest level of soluble silicon was found in chocolate puddings: 0.36–0.41 mg/serving. The silicon level in servings of the studied instant products when prepared with the appropriate amount of water was also estimated. The mean content of silicon determined in samples of drinking water from Wroc?aw and the vicinity, which was used for the estimation, amounted to 7.09 mg/l. The total silicon content in ready-to-eat products ranged from 1.32 to 39.21 mg/serving. In conclusion, some of the analyzed instant foods contained very high amounts of silicon, however the content of the soluble, and hence available, form of this element was low.     

Caffeine and Theobromine Levels in Cocoa and Carob Products

Seventy-nine cocoa or chocolate products and eighteen carob products were analyzed by HPLC for caffeine and theobromine content. After extraction into boiling water, the methylxanthines were identified and quantified with the use of a reverse phase column. Mean theobromine and caffeine levels respectively, were 0.695 mg/g and 0.071 mg/g in cocoa cereals; 1.47 mg/g and 0.152 mg/g in chocolate bakery products; 1.95 mg/g and 0.138 mg/g in chocolate toppings; 2.66 mg/g and 0.208 mg/g in cocoa beverages; 0.621 mg/g and 0.032 mg/g in chocolate ice creams; 0.226 mg/g and 0.011 mg/g in chocolate milks; 74.8 mg/serving and 6.5 mg/serving in chocolate puddings. Theobromine and caffeine levels in carob products ranged from 0-0.504 mg/g and 0-0.067 mg/g, respectively.     

发酵和焙烤对可可豆多酚、黄酮和风味品质的影响

本实验采用高效液相色谱仪（high performance liquid chromatography,HPLC）、色差仪、电子鼻分别检测未发酵、发酵和焙烤海南可可豆的总酚含量、总黄酮含量、色度和可可豆风味差异。结果表明：未经焙烤的未发酵豆总酚（464.03 mg/10 g）和总黄酮（126.86 mg/10 g）含量明显高于发酵豆总酚（211.86 mg/10 g）和总黄酮（61.98 mg/10 g）含量。105～145 ℃焙烤30 min,未发酵豆总酚和总黄酮含量分别为419.5～129.8 mg/10 g和77.8～16.8 mg/10 g;发酵豆总酚和总黄酮含量分别为182.53～86.25 mg/10 g和34.7～7.0 mg/10 g。其中,125 ℃焙烤20～40 min,未发酵豆总酚和黄酮含量分别为353.74～289.45 mg/10 g和42.86～32.20 mg/10 g;发酵豆总酚和黄酮含量分别为152.08～123.55 mg/10 g和25.12～21.14 mg/10 g。在105～145 ℃的温度焙烤下没食子酸含量变化显著。可可豆色度值的范围：L*值集中在40.0～47.0之间,a*值集中在5.0～6.8之间,b*值集中在4.0～8.5之间。未发酵和发酵可可豆之间,以及不同温度焙烤可可豆之间的电子感官风味分析结果差异较大。     

Quantification of 3-aminopropionamide in cocoa, coffee and cereal products

Based on recent results confirming 3-aminopropionamide (3-APA) as a very effective precursor of acrylamide in the absence of further “catalysts”, this compound was quantified for the first time in cocoa masses, cocoa beans, coffee and cereal products by LC–MS–MS after derivatisation with dansyl chloride. Cocoa masses contained >3000 μg/kg of 3-APA, but varied significantly in its concentration. For the quantification of acrylamide (AA) in cocoa and coffee, an improved isolation procedure using charcoal was developed. In various samples of unroasted and roasted cocoa beans, the concentrations of AA were by a factor of >5 lower than those of 3-APA, but the concentrations of 3-APA and AA were more closely correlated as compared to the concentrations of AA and Asparagine. Experiments on authentic cocoa beans from Ghana and Sulawesi indicated that the thermal generation of 3-APA during roasting was much more pronounced as compared to its biochemical formation. By administering fermented cocoa beans with [¹³C₄ ¹⁵N₂]-asparagine before roasting, 3-APA was confirmed as transient intermediate in AA formation during cocoa roasting. Among the cereal products analysed, in particular popcorn contained quite high amounts of 3-APA, which were also well correlated with the AA concentration. Contrary, in coffee products, 3-APA was always lower than AA.     

梁王茶叶及其速溶茶粉的化学成分分析和抗氧化研究

以掌叶梁王茶叶为原料制备速溶茶粉,并研究其化学成分和抗氧化性,为梁王茶的深度开发提供科学依据。采用热水浸提法制备速溶茶粉,通过比色法研究梁王茶叶及其速溶茶粉的化学组分及其抗氧化能力,并对梁王茶叶17种游离氨基酸进行测定。结果表明,梁王茶叶的主要化学组分为:水溶性总糖47.32 g/kg、总多酚13.76 g/kg、水溶性蛋白质9.58 g/kg、水溶性氨基酸5.91 g/kg、水溶性多糖1.89 g/kg、总黄酮0.88 g/kg。梁王茶叶含量最多的游离氨基酸是组氨酸45.74 mg/kg。梁王茶叶速溶茶粉的最佳浸提条件为料液比1∶30(g/mL),温度85℃,浸提60 min,浸提次数3次,此条件下速溶茶粉的提取率达到39.88%。所得梁王茶叶速溶茶粉的主要化学组分为:水溶性总糖236.05 g/kg、水溶性蛋白质99.47 g/kg、水溶性氨基酸30.83 g/kg、总多酚27.08 g/kg、水溶性多糖17.99 g/kg、总黄酮2.03 g/kg。梁王茶叶及其速溶茶粉清除DPPH自由基的IC50分别为3.92、1.60 mg/mL;清除ABTS自由基的IC50分别为12.84、1.36 mg/mL。速溶茶粉浓度为3.5 mg/mL时,其还原力为3.343;茶叶浓度为15 mg/mL时,其还原力为2.966。研究表明梁王茶叶速溶茶粉营养丰富,并含有一定量的多酚、黄酮及多糖等生物活性成分,有较强的抗氧化能力,是一款较为健康的速溶茶饮品。     

Availability of aluminium from tea and coffee

 The amount of aluminium in different kinds of tea and ground coffee was analysed, the transfer of aluminium into the infusion was determined and aluminium intake via tea and coffee was calculated within the framework of our investigations. Aluminium concentrations amounted to (in μg/g dry matter): black tea, 899; flavoured black tea, 763; peppermint tea, 477; mountain herbal tea, 419; fruit tea, 292; ground coffee, 19. About 30% of the aluminium stored in black tea’s dry matter was transferred into the infusion, which contained 4.2 mg Al/l. In contrast, the availability of aluminium from peppermint and fruit tea as well as from ground coffee was very low (about 5%). The calculated aluminium intake via tea and coffee was 0.2 to 0.3 mg/day and contributed about 5% to the total aluminium intake. Only black tea infusions are a significant source of aluminium intake via beverages. Received: 9 January 1997     

Determination of chromium(VI) in black,green and herbal teas

Speciation analysis of black, green and herbal teas was carried out by treating the samples with 0.1 M Na₂CO₃ to determine total Cr(VI) and acid digestion (of tea samples in a microwave) was applied to determine the total chromium concentrations by graphite furnace atomic absorption spectrometry (GF-AAS). The Cr(VI) content that could be consumed per unit cup of tea was determined by soaking the leaf or tea bag (or infusion) in 200 mL boiled water and the solution was filtered through a PDVF 0.45 μm hydrophilic filter prior analysis by GF-AAS.     

Aflatoxins and ochratoxin A in tea prepared from naturally contaminated powdered ginger

The migration of several major mycotoxins, aflatoxins B₁ (AFB₁), B₂, G₁, and G₂ (AFT, total of the aflatoxins) and ochratoxin A (OTA), from naturally contaminated powdered ginger to surrounding liquid (tea) was investigated. The toxins are commonly found in cereal grains and are toxic, carcinogenic and thermostable. Ginger root is widely used for digestive problems. Powdered ginger (2 g) found to contain AFT and OTA was placed in an empty heat sealable tea bag. The tea bag was heat-sealed and used to prepare tea under different conditions: temperature (50 and 100°C), time (5 and 10 min) and volume (100 and 200 ml). The tea bag was placed in hot water and stirred every 1 min for 5 s during the first 5 min of steeping. After steeping, the tea bag was removed and the tea and ginger residue (in the tea bag) were analysed separately for AFT and OTA. After extraction and immunoaffinity column (IAC) clean-up, the isolated AFT and OTA were separated by reversed-phase liquid chromatography and quantified using a fluorescence detector. At 100°C, approximately 30–40% of AFB₁ and AFT and 20–30% of OTA in the contaminated ginger were found in the ginger tea; the total amounts of AFT and OTA in tea varied less than 5% under the three conditions of preparation. At 50°C, about 10% of OTA and AFT were found in tea. This is the first study on the migration of AFT from botanicals to tea. It is also the first to study the distribution of AFT and OTA from powdered ginger to tea and ginger residue.     

An investigation on the appropriateness of chocolate to match tea and coffee

The aim of this study was to provide some recommendations for selecting a befitting tea and coffee to match chocolate with different cocoa contents. Three coffee samples (chocolate flavored, vanilla flavored and unflavored coffee), four tea samples (black tea, green tea, vanilla flavored tea and citrus flavored tea) and three chocolates (30%, 70%, and 99% cocoa) were hedonically rated by eighty regular chocolate consumers. The beverages were then paired with each chocolate, and the consumers were asked to indicate the hedonic liking of the resulting pairings, and to indicate whether the chocolate or beverage flavor dominated the pairing flavor. This study showed that liking of chocolate and coffee pairings and chocolate and tea pairings significantly varied (p < 0.001) across samples. Consumers preferred pairings with 30% cocoa and 70% cocoa chocolate to pairings with 99% cocoa chocolate. Overall, coffee is significantly (p < 0.001) preferred to tea as a chocolate partner.Chocolate and beverage pairing liking was biased by the liking of the beverage tasted alone, the liking of chocolate tasted alone, beverage type, chocolate type and the level of flavor match between chocolate and tea or coffee in a given pairing. When chocolate and beverage flavor balanced out in a given pairing, chocolate and coffee/tea pairings were significantly preferred by the consumers. A significant decrease in acceptance was observed when beverage or chocolate flavor dominated the flavor of the pairing, much more so when the chocolate flavor dominated the pairing flavor. However consumers don't enjoy any preferred chocolate with any preferred tea or coffee because some flavors match better than do others. Indeed, consumers formulate their hedonic responses taking into consideration what flavors go well together more than they rely exclusively on their hedonic judgments of the chocolates, the teas, and the coffees tasted alone.     

ANALYSIS OF COFFEE, TEA AND ARTIFICIALLY FLAVORED DRINKS PREPARED FROM MINERALIZED WATERS

ABSTRACT— Coffee, black tea and artificially flavored and artificially sweetened orange and grape soft drinks were prepared from solutions of 8 minerals each at 750 ppm. Additionally, coffee and tea were brewed, using 6 natural drinking waters which ranged from 42–1,725 ppm of total dissolved solids. Beverages made from solutions containing carbonates were the least desirable, having flat, insipid characteristics. Although distilled water resulted in an acceptable soft drink, coffee and tea prepared from it were excessively sour and astringent, respectively. The recommended formula of 53.3 g of coffee per liter of water was considered too strong and "burnt' for the panel of trained judges, so that the experiments were repeated at a lower concentration of 47 g coffee/liter water. Large differences in the direction and magnitude of the visual characteristics of the coffee and tea brewed from the various waters also were observed in the marked changes in luminous transreflectance, purity and shifts in dominant wavelengths measured by thin-layer reflectometry.     

2- and 3-Monochloropropanediols in paper products and their transfer to foods

The occurrence of 2- and 3-monochloropropanediol (MCPDs) in selected paper products sold on the Canadian market and the transfer of 3-MCPD from those products to beverages was probed. Products included coffee filters, tea bags, disposable paper hot beverage cups and milk packaged in paperboard containers. The occurrence MCPDs in coffee and tea filters on the German market was investigated as well. Furthermore, the presence of MCPDs in paper towels on the German market was also investigated. Analytes were determined by stable isotope dilution analysis GC-MS in SIM mode. 3-MCPD was detected in most paper products with levels ranging from a few nanograms in tea bags to a few micrograms in white coffee filters. Milk containers’ paperboard contained 3-MCPD at about 500–1500 ng g^–1; however, 3-MCPD was detected in milk only in smaller containers, 237–500 ml (likely due to a lower volume/surface ratio) at levels of about 1 ng g^–1. Out of three disposable hot beverage paper cups tested (of 237–473 ml capacity), paperboard of two contained 3-MCPD at 632–792 ng g^–1, and 3-MCPD was detected in leachate from those paper cups at levels of about 16 ng per cup. 3-MCPD was detected in all paper towels at levels of 42–2466 ng g^–1. 2-MCPD was detected in many paper products (from Canadian and German sources) and in all the towels tested at levels varying from about 0.5–10% of that of 3-MCPD.     

基于单宁酶处理原料制备的高茶黄素速溶红茶品质分析

目的 研究基于单宁酶发酵加工的红茶原料,制备高茶黄素含量的速溶红茶。方法 以速溶红茶中的茶黄素含量为主要评价指标,对红茶原料进行两种提取溶剂处理和不同茶叶状态,即茶叶和茶叶磨碎样处理,同时分析其感官品质及其它化学成分含量。结果 本研究发现用60%乙醇提取工艺制备的速溶红茶中,茶黄素含量显著高于水提取工艺,茶叶状态则是茶粉原料浸提效果显著高于茶叶原料浸提效果,且速溶红茶中茶黄素含量达到2.3%,是传统红茶原料中茶黄素的3倍,速溶红茶得率达到了38%。结论 以高茶黄素茶叶为原料,并将其磨成粉,用60%乙醇提取作为提取剂制备速溶红茶,其制备的速溶红茶富含茶黄素,为速溶茶的生产加工提供了一定的理论依据,也可以为夏秋茶资源的开发利用提供新方法。     

Preservation of Cocoa Antioxidant Activity, Total Polyphenols, Flavan-3-ols, and Procyanidin Content in Foods Prepared with Cocoa Powder

ABSTRACT:  Little is known about the effects of common cooking processes on cocoa flavanols. Antioxidant activity, total polyphenols (TP), flavanol monomers, and procyanidin oligomers were determined in chocolate frosting, a hot cocoa drink, chocolate cookies, and chocolate cake made with natural cocoa powder. Recoveries of antioxidant activity, TP, flavanol monomers, and procyanidins ranged from 86% to over 100% in the chocolate frosting, hot cocoa drink, and chocolate cookies. Losses were greatest in the chocolate cake with recoveries ranging from 5% for epicatechin to 54% for antioxidant activity. The causes of losses in baked chocolate cakes were investigated by exchanging baking soda with baking powder or combinations of the 2 leavening agents. Use of baking soda as a leavening agent was associated with increased pH and darkening color of cakes. Losses of antioxidant activity, TP, flavanol monomers, and procyanidins were associated with an increased extractable pH of the baked cakes. Chocolate cakes made with baking powder for leavening resulted in an average extractable pH of 6.2 with essentially complete retention of antioxidant activity and flavanol content, but with reduced cake heights and lighter cake color. Commercially available chocolate cake mixes had final pHs above 8.3 and contained no detectable monomeric flavanols after baking. These results suggest that baking soda causes an increase in pH and subsequent destruction of flavanol compounds and antioxidant activity. Use of an appropriate leavening agent to moderate the final cake pH to approximately 7.25 or less results in both good leavening and preservation of cocoa flavanols and procyanidins.     

高效液相色谱-二极管阵列法检测四川绿茶、黄茶、黑茶、红茶和青茶中甲基化儿茶素含量

采用高效液相色谱-二极管阵列检测法(HPLC-DAD)对四川省雅安、成都、乐山、宜宾、绵阳23家企业生产的绿茶、黄茶、黑茶、红茶和青茶中48个茶样的(-)-表没食子儿茶素-3-O(3-O-甲基)没食子酸酯(EGCG3″Me)含量进行了比较研究。结果表明:青茶EGCG3″Me含量最高,在3.14~6.08 mg/g之间,平均值为4.40 mg/g;黑茶EGCG3″Me含量在0~1.72 mg/g,平均值为0.35 mg/g;绿茶和黄茶中EGCG3″Me含量较低;绿茶中含量在0~0.39 mg/g之间,平均值为0.10 mg/g;黄茶中含量在0~0.09 mg/g之间,平均值为0.05 mg/g;红茶中未检出。各茶类间EGCG3″Me含量差异显著,主要原因在于加工所用鲜叶原料(品种、采摘标准等)及加工工艺等不同。建议易过敏人群应适当饮用青茶。