Pyrrolizidine and tropane alkaloids in teas and the herbal teas peppermint,rooibos and chamomile in the Israeli market

Dehydro pyrrolizidine alkaloids (dehydro PAs) are carcinogenic phytotoxins prevalent in the Boraginaceae, Asteraceae and Fabaceae families. Dehydro PAs enter the food and feed chain by co-harvesting of crops intended for human and animal consumption as well as by carry-over into animal-based products such as milk, eggs and honey. Recently the occurrence of dehydro PAs in teas and herbal teas has gained increasing attention from the EU, due to the high levels of dehydro PAs found in commercially available teas and herbal teas in Germany and Switzerland. Furthermore, several tropane alkaloids (TAs, e.g. scopolamine and hyoscyamine) intoxications due to the consumption of contaminated herbal teas were reported in the literature. The aim of the present study was to determine the dehydro PAs and TAs levels in 70 pre-packed teabags of herbal and non-herbal tea types sold in supermarkets in Israel. Chamomile, peppermint and rooibos teas contained high dehydro PAs levels in almost all samples analysed. Lower amounts were detected in black and green teas, while no dehydro PAs were found in fennel and melissa herbal teas. Total dehydro PAs concentrations in chamomile, peppermint and rooibos teas ranged from 20 to 1729 μg/kg. Except for black tea containing only mono-ester retrorsine-type dehydro PAs, all other teas and herbal teas showed mixed patterns of dehydro PA ester types, indicating a contamination by various weed species during harvesting and/or production. The TA levels per teabag were below the recommended acute reference dose; however, the positive findings of TAs in all peppermint tea samples warrant a more extensive survey. The partially high levels of dehydro PAs found in teas and herbal teas present an urgent warning letter to the regulatory authorities to perform routine quality control analysis and implement maximum residual levels for dehydro PAs.     

Simulated intestinal digestion of green and black teas

Previous studies have shown that significant changes to green tea catechins occur as a result of changes in pH similar to those found in the gastrointestinal tract. In this study we have demonstrated that the sum of the antioxidant activities attributable to the four major catechins in brewed green and black tea samples was less than the total measured antioxidant activity, although there was a high degree of correlation between antioxidant activity and total measured polyphenol concentration. In addition, incubation of either form of tea at acid pH (as found in the stomach) had little effect of the concentration of individual catechins. However, incubation at slightly alkaline pH, similar to that found in the small intestine, resulted in a rapid decline in the concentrations of both green and black tea catechins, but with a lesser reduction in antioxidant activity and polyphenol concentration.     

Effect of green and black teas (Camellia sinensis L.) on the characteristic microflora of yogurt during fermentation and refrigerated storage

The effect of tea on the fermentation and survival of yogurt microorganisms was studied. Green and black teas were added to milk at the beginning of fermentation. Acidity of yogurt products and survival of their microflora were studied during 42 days at 4 °C. Results showed that the presence of tea did not significantly (P < 0.05) influence the yogurt characteristic microorganisms. HPLC studies demonstrated that yogurt bacteria did not affect tea catechins when they were incubated together for 48 h. Indeed, all five products reached about 10⁹ CFU/ml after 6 h of fermentation. Viability during 6 weeks storage at 4 °C varied very little (8.35 < log CFU/ml < 8.65). Similarly, green and black teas had no effect on lactic acid levels of the final products (after 6 weeks of storage, acidity remained above 80 °D). According to these findings, addition of teas or tea catechins to yogurt can be recommended to take advantage of their beneficial properties on human health attributed to their antioxidant and antimicrobial activities.     

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.     

Survival of Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes on inoculated walnut kernels during storage

The survival of single strains or cocktails of Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes was evaluated on walnut kernels. Kernels were separately inoculated with an aqueous preparation of the pathogens at 3 to 10 log CFU/g, dried for 7 days, and then stored at 23°C for 3 weeks to more than 1 year. A rapid decrease of 1 to greater than 4 log CFU/g was observed as the inoculum dried. In some cases, the time of storage at 23°C did not influence bacterial levels, and in other cases the calculated rates of decline for Salmonella (0.05 to 0.35 log CFU/g per month) and E. coli O157:H7 (0.21 to 0.86 log CFU/g per month) overlapped and were both lower than the range of calculated declines for L. monocytogenes (1.1 to 1.3 log CFU/g per month). In a separate study, kernels were inoculated with Salmonella Enteritidis PT 30 at 4.2 log CFU/g, dried (final level, 1.9 log CFU/g), and stored at -20, 4, and 23°C for 1 year. Salmonella Enteritidis PT 30 declined at a rate of 0.10 log CFU/g per month at 23°C; storage time did not significantly affect levels on kernels stored at -20 or 4°C. These results indicate the long-term viability of Salmonella, E. coli O157:H7, and L. monocytogenes on walnut kernels and support inclusion of these organisms in hazard assessments.     

Reactions of green and black teas with Cu(II)

Electron paramagnetic resonance (EPR) measurements of the products of reactions between Cu(II) and samples of green and black teas showed spectral components from at least six different Cu(II) complexes with both tea types. Several of these complexes were common to both teas in spite of major differences in their polyphenol compositions. The pH range observed for complex formation, and the total signal intensity in the pH range 4-8, were greatly different from those for the reactions of Cu(II) with (-)-epigallocatechin gallate and gallic acid, the main polyphenols responsible for the free radical signals observed during oxidation of these beverages. Components with spectral parameters similar to those of Cu(II) complexes with theanine, the major amino acid in tea, may contribute to two of the spectra recorded under acidic conditions. However, the initial complexes formed at the lowest pH values investigated are still unidentified. EPR spectra with parameters consistent with Cu(II) polyphenol complexes were only observed under alkaline conditions, thus suggesting that components of tea other than polyphenols might be more important in reactions with copper, and possibly other transition metals, in solutions under physiological conditions.     

The analysis by HPLC of green,black and Pu'er teas produced in Yunnan

Samples of tea (Quingmao, steamed, black and Pu'er) produced in Yunnan Province, People's Republic of China, from the locally characteristic large-leaved Camellia sinensis, have been brewed and the brews analysed for their contents of flavonol glycosides, flavan-3-ols and their oxidation products. Several samples of Pu'er tea manufactured in the 1920s, 1930s and 1940s were also examined. The brews prepared from Quingmao tea and steamed green tea leaf were very similar containing primarily flavan-3-ols accompanied by flavonol glycosides, theogallin and gallic acid. The profile of flavanols was unusual, being dominated by (?)-epicatechingallate (rather than (?)-epigallocatechingallate) and by an unusually large (+)-catechin content. The brew of the equivalent black tea retained significant amounts of residual flavanols (particularly (?)-epicatechingallate and (+)-catechin), and contained significant amounts of thearubigins, theaflavic acids and theaflavins (including the less common analogues probably derived from the oxidation of (+)-catechin). The brews prepared from the Puer teas were distinguishable from the black tea brew by the absence of theaflavins and theaflavic acids, and by much smaller residues of flavanois and flavonol glycosides. The contents of thearubigins varied considerably whereas those of gallic acid were similar.     

Survival of Escherichia coli O157:H7 during storage in pressure-treated orange juice.

The effect of a high-pressure treatment on the survival of a pressure-resistant strain of Escherichia coli O157:H7 (NCTC 12079) in orange juice during storage at 3 degrees C was investigated over the pH range of 3.4 to 5.0. The pH of shelf-stable orange juice was adjusted to 3.4, 3.6, 3.9, 4.5, and 5.0 and inoculated with 10(8) CFU ml(-1) of E. coli O157:H7. The orange juice was then pressure treated at 400 MPa for 1 min at 10 degrees C or was held at ambient pressure (as a control). Surviving E. coli O157:H7 cells were enumerated at 1-day intervals during a storage period of 25 days at 3 degrees C. Survival of E. coli O157:H7 during storage was dependent on the pH of the orange juice. The application of high pressure prior to storage significantly increased the susceptibility of E. coli O157:H7 to high acidity. For example, after pressure treatment, the time required for a 5-log decrease in cell numbers was reduced from 13 to 3 days at pH 3.4, from 16 to 6 days at pH 3.6, and from >25 to 8 days at pH 3.9. It is evident that the use of high-pressure processing of orange juice in order to increase the juice's shelf-life and to inactivate pathogens has the added advantage that it sensitizes E. coli O157:H7 to the high acid conditions found in orange juice, which results in the survival of significantly fewer E. coli O157:H7 during subsequent refrigerated storage.     

绿茶、红茶加工工艺对茶鲜叶中多酚类物质的影响

采用槠叶种一芽二、三叶鲜叶,按照传统的加工工艺分别制成绿茶和红茶。以鲜叶为对照,应用分光光度法和RP—HPLC法对绿茶、红茶的多酚类物质进行了分析,结果表明:与鲜叶相比,(1)绿茶中多酚类物质总量保持不变,而红茶中多酚类物质总量下降了43.8%;(2)绿茶中儿茶素总量几乎不变,而红茶下降了80.6%;(3)红茶中茶黄素和茶红素分别上升了565.5%和74.5%。     

Survival of enterohaemorrhagic Escherichia coli O157:H7 strain in Turkish soudjouck during fermentation, drying and storage periods

Soudjouck (a kind of Turkish sausage) batter was inoculated with Escherichia coli O157:H7 at a level of 10⁵ colony-forming unit (CFUg) and kept overnight at 4°C. After stuffing the soudjouck batter into natural casing, fermentation was carried out at 24±2°C and 90–95% relative humidity (RH) for 3 days with subsequent drying at 22±2°C and 80–85% RH for 5 days. Then, half of soudjouck samples were vacuum-packed in polyethylene bags and the rest were kept open. All samples were stored at 4°C (55% RH) for 3 months. E. coli O157:H7 and lactic acid bacteria counts, moisture contents and pH values of the samples were determined during fermentation, drying and storage periods. Results showed that count of E. coli O157:H7 decreased by 3 log unit during fermentation and drying periods. It was observed that this pathogen survived longer in vacuum-packaged samples (more than 2 months) than non-vacuum samples (more than 1 month).     

Survival of Escherichia coli, strain W, during the manufacture of cottage cheese.

Cottage cheese was manufactured in 10-liter experimental vats by the direct-acid-set method from milk that was inoculated with a heat resistant strain of Escherichia coli. Growth or survival of Strain W (ATCC 9637) E. coli was determined at various stages of the cheese making operation after the cheese-skim milk was inoculated to give counts of 2.5 X 10(4) or 4.0 X 10(5) cells/ml. Numbers of coliform organisms remained constant at the inoculated concentration in the cheese milk up to a cooking temperature of 43 C. At 43 C, when curd was separated from the whey, the curd (not washed) had coliform counts that were two log cycles greater than the whey. These trends were in milks with both cell counts. Washing of the curd with acid and 10 ppm chlorine reduced the number of coliform cells in the curd at all cooking temperatures as compared with unwashed curd. Acid wash of the curd at pH 5 did not reduce the coliform counts below those of unwashed curd. Cooking temperatures of 54 C were necessary to destroy (less than 1 cell/ml) E. coli Strain W, in either the unwashed or acid-chlorine washed curd. Holding curd with an initial average log count of 6.26 coliform cells/ml at constant temperatures of 38, 43, 49, and 54 C confirmed that 54 C for 50 min was necessary to reduce the average count to less than 1 cell/ml in isolated curd. Coliforms in whey were reduced to that concentration after 10 min at 54 C.     

绿茶、乌龙茶、红茶贮藏过程中品质劣变机理及保鲜技术研究进展

茶叶的生产具有较强的时效性和季节性,且茶叶疏松多孔,长期贮藏过程中极易受环境影响而变质。作为广受消费者青睐的世界三大饮料之一,保持其贮藏品质对提高茶叶商品价值,推进我国茶产业的发展具有重要意义。近年来针对茶叶贮藏过程中的品质变化原因兴起了各种保鲜技术。该文通过讨论茶多酚、氨基酸、维生素C、叶绿素、脂质等物质的氧化降解,总结了绿茶、乌龙茶、红茶等的陈化劣变机理,同时概述了水分、温度、氧气、光照等影响茶叶贮藏品质的4大因素,并详细阐述了运用干燥、冷藏、脱氧、生物保鲜剂等方法进行茶叶贮藏的相关技术,最后展望了茶叶保鲜的深入研究方向,以期为相关茶叶保鲜新技术的研究提供科学理论指导。     

Characterisation of catechins in green and black teas using square-wave voltammetry and RP-HPLC-ECD

Eight green and three black teas have been analysed using square-wave voltammetry at a glassy-carbon electrode, at pH 2 and square-wave frequency 100 Hz. The SWV response of teas consisted of two partially resolved anodic peaks: peak 1 at around 0.372 V, and peak 2 around 0.491 V. First anodic peak was due to oxidation of pyrogallol catechins, i.e. epigallocatechin gallate (EGCG) and epigallocatechin (EGC), and peak 2 can be associated with oxidation of ortho-hydroquinone and galloyl groups in catechins, gallic acid, theaflavins, and other catechol-type phenolics present in tea. Peak 1 has been chosen for quantification purposes, and concentrations of catechins were calculated from the calibration plot constructed for EGC used as external standard. Amounts of catechins in green teas obtained by SWV were in good agreement with those obtained using reverse-phase high-performance liquid chromatography with electrochemical detection (RP-HPLC-ECD). For black tea samples the detector response of peak 1 was diminished due to interferences of coexisting polyphenols, and SWV obtained results were something lower than those obtained by HPLC-ECD.     

Attachment of shiga toxigenic Escherichia coli to beef muscle and adipose tissue

Shiga toxigenic Escherichia coli (STEC) serotypes are important foodborne pathogens that cause gastrointestinal disease worldwide. An understanding of how STEC strains attach to surfaces may provide insight into the potential persistence of and contamination with STEC in food environments. The initial attachment of a selection of STEC serotypes to beef muscle and adipose tissue was evaluated for isolates grown in planktonic and sessile culture. Initial experiments were performed to determine whether attachment differed among STEC strains and between the two modes of growth. Viable counts were obtained for loosely and strongly attached cells, and the strength of attachment (Sr) was calculated. All bacterial isolates grown in sessile culture attached in higher numbers to muscle and adipose tissue than did bacteria in planktonic cultures. For all attachment assays performed, mean concentrations for loosely attached cells were consistently higher than concentrations for strongly attached cells. The mean concentrations for strongly attached bacteria for planktonic and sessile cultures were significantly higher (P < 0.05) on adipose than on muscle tissue. However, some strains of STEC, particularly those from sessile culture, did not differ in their attachment to muscle or adipose tissue. Sr values were not significantly different (P > 0.05) among STEC isolates for all assays. No correlation was found between bacterial hydrophobicity and surface charge values (previously determined) and production of surface structures, viable counts, and Sr values. STEC grown in planktonic and sessile culture seems to behave differently with respect to attachment to muscle and adipose tissue. Cells in sessile culture may have a greater potential to strongly attach to meat surfaces.     

Rheological behaviour and colour changes of ginger paste during storage

Ginger paste was prepared from fresh ginger by addition of 8% common salt and citric acid. The paste was thermally processed and packed in glass, polyethyleneterephthalate or high‐density‐polyethylene containers and stored at 5 ± 1 and 25 ± 1 °C for 120 days. The rheological characteristics of the paste were studied by using a computer controlled rotational viscometer over the temperature range of 20–80 °C. Samples were subjected to a programmed shear rate, increasing linearly from 0 to 200 s^?1 in 3 min, followed by a steady shear at 200 s^?1 for 3 min and finally decreasing linearly from 200 to 0 s^?1 in 3 min. Ginger paste exhibited pseudoplasticity with yield stress and flow adequately described by the Herschel–Bulkley model. The yield stress decreased exponentially with process temperature and ranged between 3.86 and 27.82 Pa. The flow behaviour index (n) varied between 0.66 and 0.82 over the temperature range. Both consistency index and apparent viscosity decreased with increase in temperature and the process activation energies were found to be in the range of 16.7 to 21.9 kJ mol^?1. The effect of temperature was significant (P < 0.05) on the Hunter colour combination value of the paste during storage; however it was not affected by type of packaging material (P > 0.05). It is recommended that ginger paste is stored at 5 ± 1 °C in polyethyleneterephthalate or glass containers.     

GC-IRMS analysis of black Ceylon, Assam and Darjeeling teas

 The δ¹³C_PDB values of characteristic flavour compounds of black Ceylon, Darjeeling and Assam teas were determined using gas chromatography-isotope ratio mass spectrometry. The influence of different harvest times, years and various cultivation regions on the δ¹³C_PDB and the δ¹³C _{cis linalool oxide (fur.)} values were investigated. By comparison with suitable internal isotopic standards, adulterations with methyl salicylate were detectable. Received: 22 July 1998     

Effect of cumin,cinnamon, ginger,mustard and tamarind in induced hypercholesterolemic rats

The effect of a few common spices - cumin (Cuminum cyminum), cinnamon (Cinnamomum zeylanicum), ginger (Zingiber officinale), mustard (Brassica nigra) and tamarind (Tamarindus indica) - added to normal and hypercholesterolemia inducing diet on serum and liver cholesterol levels in rats was studied. These spices did not show any cholesterol lowering effect when included in the diet at about 5-fold the normal human intake level.     

Induction of γ irradiation for decontamination and to increase the storage stability of black teas

The handling and storage of black tea at high humidity increases its moisture content, which encourages microbial growth. γ irradiation is one of the most efficient techniques for the reduction of microorganisms in food. The present study aimed to evaluate the effect of γ irradiation on black tea quality and microbial load, during storage. Irradiation had a significant effect on reducing the microbial load, while untreated samples had a high microbial load. Untreated samples absorbed moisture up to 8.65% in 12 months time, whereas it was 6.0% in the case of irradiated samples. The quality of the irradiated teas exhibited stability in major parameters like theaflavin (TF), thearubigin (TR), highly polymerized substances (HPS), and total liquor colour (TLC). There was no significant difference among the quality characteristics of 7 kGy and 10 kGy irradiated samples during the entire period of storage when compared with 0 day control. Results indicated a deterioration in quality of well packed, but untreated control samples during storage. Irradiation resulted in complete removal of microbes and extended the shelf life of black tea.     

酱油等调味品中大肠杆菌存活与分析

分析大肠杆菌在酱油中的存活特性,为酱油等调味品的卫生控制和检测提供技术指导。将购置的标准大肠杆菌菌株和从酱料中分离的野生型大肠杆菌人工接到大肠杆菌阴性的不同品种和厂家的瓶装酱油中,采用国家标准方法定期检测大肠杆菌的个数,计算大肠杆菌的存活时间,对大肠杆菌在不同品种和不同厂家酱油中的时间的存活率进行了研究。结果表明,不同种类大肠杆菌在酱油中存活时间不同,同种大肠杆菌在老抽系列酱油中的存活时间长于在生抽酱油的存活时间,时间长2 d~4 d,而在生抽中存活时间为1 d,存活时间短于以前的报道。同时普查了大肠杆菌在国内其他厂家酱油中的存活时间,发现存活时间多为1 d~2 d,并且不同种类存活时间存在差异。大肠杆菌在酱油中致死现象和机制有待进一步分析,该研究为当前控制酱油中大肠杆菌的污染问题提出了新的证据和启示。     

GC-IRMS analysis of black Ceylon, Assam and Darjeeling teas

 The δ¹³C_PDB values of characteristic flavour compounds of black Ceylon, Darjeeling and Assam teas were determined using gas chromatography-isotope ratio mass spectrometry. The influence of different harvest times, years and various cultivation regions on the δ¹³C_PDB and the δ¹³C _{cis linalool oxide (fur.)} values were investigated. By comparison with suitable internal isotopic standards, adulterations with methyl salicylate were detectable.