Aqueous extract of citrus peel reduces production of hydrogen peroxide in catechin-enriched green tea

Hydrogen peroxide (H₂O₂) is gradually produced in bottle-packed beverages, including tea and coffee, after the cap has been opened, i.e, through exposure to air, though only a small amount of H₂O₂ is detected in the beverage immediately after the bottle is opened. Since, H₂O₂ is toxic, it is necessary to develop safe and simple ways of reducing its production in bottled beverages. The addition of an aqueous extract of citrus peel reduced the concentration of H₂O₂ in green tea. To characterise the active constituents in the citrus peel, the aqueous extract of the peel was fractionated using chloroform, ethyl acetate, and butanol, in that order, and subjected to gel chromatography. The active constituents in the citrus peel were water-soluble compounds of various molecular weights.     

儿茶素的两种浸提工艺的优化及比较

浸提是儿茶素生产的重要步骤,对总收率和后续的分离提纯有直接的影响。本文以茶多酚、儿茶素、咖啡碱的得率为指标,比较浸提温度、时间、液固比、浸提次数对热水浸提和80％的醇水溶液浸提两种方法的不同影响获得两种浸提方法的适宜工艺条件。在此基础上,对两种方法的生产总成本进行了技术经济分析,表明醇水浸提法生产成本与水浸提法之比约为1．15,两种方法适合于不同产品要求的生产。     

A new catechin oxidation product and polymeric polyphenols of post-fermented tea

A new epicatechin oxidation product with a 3,6-dihydro-6-oxo-2H-pyran-2-carboxylic acid moiety was isolated from a commercially available post-fermented tea that is produced by microbial fermentation of green tea. The structure of this product was determined by spectroscopic methods. A production mechanism that includes the oxygenative cleavage of the catechol B-ring of (−)−epicatechin is proposed. In addition, polymeric polyphenols were separated from the post-fermented tea and partially characterised by ¹³C NMR spectroscopy and gel-permeation chromatography. The polymers appear to be primarily composed of epigalloacetechin-3-O-gallate and the molecular weight (Mn) of the acetylated form was estimated to be ∼3500.     

Antioxidative and anti-hydrogen peroxide activities of various herbal teas

Herbal teas, i.e., extracts of herbs, are popular because of their fragrance and antioxidative activity. Since the antioxidative activity comes mainly from polyphenols, total polyphenol concentrations and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activities in herbal teas were measured and compared. Levels of H₂O₂ in the teas were also examined, since the production of H₂O₂ in beverages such as coffee and green tea, has been reported. Only a small amount of H₂O₂ was detected in the herbal teas just after their preparation with hot water. However, H₂O₂ was gradually produced during incubation at 25 °C after extraction with hot water, especially when the teas were incubated in phosphate buffer at pH 7.4. To examine the anti-H₂O₂ activity of herbal teas, various teas were added to a catechin-enriched green tea, which produce much H₂O₂, and they were incubated at 25 °C for one day. Addition of hibiscus and thorn apple tea decreased the production of H₂O₂ in the catechin-enriched green tea, possibly because of a lowering of the pH of the mixture.     

Anti-hydrogen peroxide activity of fish and soy sauce

Shoyu is the Japanese name for soy sauce and the most popular liquid condiment (seasoning) used in Japanese cuisine as well as in cuisines of other oriental countries. Shoyu is prepared by digesting mold-cultured soybeans and wheat seeded with an aspergillus (koji in Japanese) in the presence of sodium chloride. Gyoshoyu is produced when the soybeans and wheat are replaced with fish. Both Shoyu and Gyoshoyu have high level of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity. Hydrogen peroxide is produced in green tea after exposure to air. To find a safe and economical method of preventing the production of H₂O₂ in green tea, effects of Shoyu and Gyoshoyu on H₂O₂ level in bottled green tea were examined. Both Shoyu and Gyoshoyu suppressed the production of H₂O₂. Gyoshoyu decomposed H₂O₂ possibly because of the presence of a thermostable catalase, while Shoyu did not. Some components of Shoyu and Gyoshoyu may be useful to suppress the production of H₂O₂ in green tea.     

A simple and rapid turbidimetric method for determining catechins in beverages

We have developed a simple and rapid turbidimetric method to determine catechins based on the fact that many polyphenols produce hydrogen peroxide in an alkaline environment and that hydrogen peroxide oxidises cerium to generate cerium oxide precipitates. Four catechins (epicatechin, epigallocatechin, epicatechin gallate, epigallocatechin gallate) aggregated with these precipitates to form massive precipitates with increased turbidity. The catechins solution (0.18 mL) was mixed with 0.02 mL of 1% CeCl₃ solution, and absorbance (650 nm) was measured immediately after agitation for 3 min using a spectrophotometer. Absorbance was strongly correlated (0.99) with the concentration of each catechin compound. For commercially bottled green tea, the estimated catechin content determined using this turbidimetric method showed better correlation with the content determined by high‐performance liquid chromatography than that determined using ferrous tartrate method, which is the official Japanese method for determining the tannin content of green tea.     

微波对茶多酚结构及其儿茶素组成的影响

以茶叶为原料，研究了微波对茶多酚结构及其儿茶素的影响，结果表明，微波短时处理茶叶，茶多酚的化学结构无明显变化，但其主要成分－－儿茶素的组成发生了变化。EGCG（表没食子儿茶素没食子酸酯）和ECG（表儿茶素没食子酸酯）两种组分有所下降，下降率分别达3．5％和3．4％，并出现GCG（没食子儿茶素没食子酸酯），增加量达5．2％，但与用沸水提取0．5h相比，儿茶素组分变化幅度小。     

茶多酚不同分散体系对葵花籽油抗氧化作用的研究

茶多酚对植物油脂具有很好的抗氧化作用,但由于它的脂溶性差而不能直接使用于油脂中。本文就茶多酚的乳化法和溶剂法两种分散体系对葵花籽油的抗氧化性进行了研究。试验结果表明:茶多酚溶剂法分散体系具有更好的抗氧化性,其最佳使用浓度为0.015％。同时,维生素E对茶多酚的抗氧化具有增效作用,对于茶多酚溶剂法分散体系,其最佳使用浓度为0.04％。     

Haze formation in beverages

The most frequent cause of hazes in beverages is due to protein-polyphenol interaction. Proteins that bind polyphenols contain proline, and the more proline, the greater the haze-forming activity. Polyphenols that cause haze have at least two sites that can bind to proteins; this enables them to cross-link proteins together and results in insoluble particles that scatter light. Protein-polyphenol interaction is non-covalent and, at least initially, reversible. The size of haze particles and the haze intensity are both affected by the ratio of haze-active (HA) polyphenol to HA protein. Alcohol content and pH also exert strong influences. Particle size in a model system does not vary smoothly as conditions change; rather shifts in the proportions of particles of a few discrete sizes are seen. Haze development occurs over time in packaged products. In clear beverages a treatment (fining, adsorption or ultrafiltration) is normally applied to reduce the concentration of either HA protein or HA polyphenol in order to delay the onset of haze formation beyond the intended product shelf life. A nephelometer observation gives a good indication of the amount of haze people can perceive.     

Amperometric determination of hydrogen peroxide residue in beverages using a Nafion modified palladium electrode

Hydrogen peroxide (H₂O₂) residues are not permitted in food due to health concerns. An amperometric sensor based on a Nafion modified palladium (Pd) electrode was developed for the rapid determination of the H₂O₂ residue in aseptically packaged beverages. A prepared Pd electrode shows a slowly increasing reaction upon repeating the procedure of adding the same concentration of H₂O₂ into the reaction cell unless pretreating the electrode with cyclic voltammetry to obtain reproducible surfaces, whereas a Nafion modified Pd electrode can reach stable reaction to H₂O₂ without any pretreatment. The interference level of ascorbic acid (the ration of electrochemical response to ascorbic acid to the electrochemical response of H₂O₂) was calculated as 0.0004 for the Nafion modified Pd electrode. Interference (99.5%)from ascorbic acid was diminished by Nafion membrane. The response of the sensor to H₂O₂ in distilled water is linear over the range of 0.25–15 μM (r ² = 0.9956). The sensor developed in this study can efficiently determine H₂O₂ residues in commercial beverages with good linear correlation between spiked H₂O₂ concentration and detected H₂O₂ concentration, for winter melon-flavored drink, r ² = 0.9904 in the range of 0.25–15 μM and for lemon-flavored tea, r ² = 0.9927 in the range of 0.25–25 μM.     

Microbial deterioration of traditional alcoholic beverages in Nigeria

A study was carried out to investigate the microbiological quality and physico-chemical changes of “aged’’ cereal-based traditional alcoholic beverages in Nigeria. There were variations in the microorganisms isolated from sekete, pito and burukutu at post-production time of 72 h, but Saccharomyces cerevisiae, Acetobacter aceti, A. hansenii, A. pasteurianus, Alcaligenes, Flavobacterium, Lactobacillus plantarum and L. brevis were common to all samples. A vinegary flavour and off-odour were the pronounced characteristics of the deteriorating beverages. The decrease in the ethanol from 3% in the fresh product to 1% at the end of 72 h retailing period is proportional to the acetic acid content of the drinks. However, slight decreases were observed for lactic, malic, succinic and formic acid constituents of the beverages. Although no enterobacteriaceae was isolated, some of the identified isolates are potentially pathogenic, and can become injurious to the health of the consumers of “aged’’ batches of the beverages.     

茶叶可溶性蛋白质含量的测定及添加PVP的效应研究

应用Ｂｒａｄｆｏｒｄ法测定成品茶中水溶性蛋白质的含量，并研究了添加ＰＶＰ试剂对测定方法以及对茶叶其它品质成分的影响。     

茶汤中多酚类物质的热力学平衡

茶叶中含有多酚类化合物、嘌呤类生物碱、氨基酸、维生素及一些香气成分，其中以茶多酚、生物碱及氨基酸含量最高，它们之间相互作用是使茶产生冷浑现象的主要原因。本文以电离平衡理论为基础，研究影响其平衡的诸多因素，探索使其保持动力学平衡状态的方法。     

由中国茶叶中提取抗氧化剂的研究

本文主要论述由15种不同的中国成品茶、半成品茶、茶树老叶中提取以多酚类化合物为主的抗氧化剂,用HPLC测定其中6种已知组分的含量。以Rancimat法和POV法测定它们在猪油中抗氧化性能。结果表明,不同的加工工艺能够显著地影响茶叶抗氧化剂的得率和抗氧化性能。同时发现,它们在抗氧化过程中达到某一个阶段后,因积累了一定数量的氧化产物或新的自由基,当其氧化性的影响超过抗氧化剂的抗氧化性的影响时,将促使油脂更快地氧化(酉合)败。     

影响乙酸乙酯对茶多酚和儿茶素萃取效果的研究

利用乙酸乙酯（EtAc）萃取茶多酚（TP）和茶儿茶素类（TC），系统探讨了茶汤浓度、pH值、离子强度和萃取温度时茶多酚和儿茶素萃取效果的影响。采用正交试验方法确定了EtAc萃取TP和TC的最佳工艺组合为：茶汤浓度4％，离子强度6％，茶汤温度30℃和pH5，按照该工艺组合萃取TP和TC具有可操作性和实用性，时工业生产有指导意义。     

Antioxidant activities of crude tea polyphenols, polysaccharides and proteins of selenium-enriched tea and regular green tea

The crude tea polyphenols, polysaccharides and proteins of regular green tea and Se-enriched green tea were investigated in vitro for antioxidant activities by auto-oxidation test (AAPH) and α,α-diphenyl-β-picrylhydrazyl (DPPH) radical scavenging method. Results showed that crude tea polyphenols of Se-enriched green tea provided the highest antioxidant activity by DPPH assay and the antioxidant activity was decreased in the order: crude tea polyphenols > crude tea proteins > tea polysaccharides. The crude protein of Se-enriched green tea was found to exhibit the highest antioxidant activity by AAPH method and the antioxidant activity was decreased in the order: crude tea proteins > tea polyphenols > tea polysaccharides. Tea polyphenols and tea polysaccharides of Se-enriched green tea presented significantly higher antioxidant activities than that of regular green tea. No significant difference of antioxidant activities was found between crude tea proteins of Se-enriched green tea and regular green tea. The combinations of Se with tea polyphenols and tea polysaccharides were responsible for the higher antioxidant activities of Se-enriched green tea than regular green tea.     

DPPH法测甘蔗提取物抗氧化活性研究

本研究对甘蔗制糖过程中的各种原料进行活性物质的提取，并用DPPH（二苯代苦味酰基自由基）法测定其抗氧化活性，同时探讨了pH、加热温度、加热时间对自由基清除率的影响。结果表明各种原料均具有较强的抗氧化活性；pH值对抗氧化活性影响很大，而加热时间温度对抗氧化活性无显著影响。初步推断该活性物质属酚类。     

Determination of hydrogen peroxide scavenging activity of phenolic acids by employing gold nanoshells precursor composites as nanoprobes

A series of phenolic acids were tested for their ability to scavenge hydrogen peroxide (H₂O₂) by using a novel enzyme-free, spectrophotometry assay. Gold nanoshells (GNSs) precursor composites were selected as the optical nanoprobes. The approach was based on the H₂O₂-induced growth of GNSs, which combines nanoscience with food/health research as an innovative detection scheme. The addition of phenolic acids inhibits the formation of complete GNSs and the corresponding peak wavelength changes rationally, which could be used as an optical signature. Among the tested samples, caffeic acid is found to be the most efficient H₂O₂-scavenger with its H₂O₂-scavenging activity being 125 × 10⁻³ μM⁻¹, whereas trans-cinnamic acid exhibits the weakest activity (0.73 × 10⁻³ μM⁻¹). Results obtained were considered on the basis of structure–activity relationships. Additionally, several tea and herb extracts were also evaluated. The presented wavelength-based detection method shows superiority in evaluating coloured samples, which avoids background interference compared with the conventional absorbance-based optical methods.