江西修水双井绿茶加工技术

本文重点论述了江西修水双井绿茶制作过程中各工序控制重点。采摘特级采雨前茶,以一芽一叶初展为主;一、二级采节前茶,一级以一芽一叶为主,二级以一芽一叶与一芽二叶约各半。摊青一般约需2-5h,杀青锅温120-150℃,先高后低,每锅投叶量300-400g。揉捻加压要轻,揉时要短。初焙温度90℃左右,以焙至叶子不粘手为适度。整形搓条锅温60-80℃,团条锅温60℃左右,约八成干时转入提毫。提毫锅温40-50℃,提至白毫显露转入复焙。复焙温度60-70℃,先高后低,焙至含水率5%-6%时下焙。     

Changes of porcine pancreas α‐amylase in activity and secondary conformations under inhibition of tea polyphenols

To investigate two‐sided functions of tea polyphenols (TP) in antinutrition and energy balance modulation, TP were extracted from Chinese green tea and used to complex porcine pancreas α‐amylase (PPA). Changes of PPA in activity and secondary conformations were analysed. Porcine pancreas α‐amylase was found sensitive to TP treatment. Tea polyphenols exhibited IC₅₀ at 0.41 mg mL^?1 against PPA and maximum inhibitory rate (98.17%) at 3.0 mg mL^?1. Tea polyphenols inhibition was concluded as noncompetitive pattern based on its unchanged Km value (0.98 mg mL^?1) for soluble starch substrate. Tea polyphenols inhibition arose from pH 1.5 to 10.14, covering gastric and intestinal environments inside body. Circular dichroism spectra analysis revealed regular changes of PPA in secondary conformations (increased proportions of α‐helix and β‐sheet) prior to its inactivation at low TP concentrations. Tea polyphenols‐inhibited PPA had distinct double‐negative peaks at 204 nm and 208 nm. Porcine pancreas α‐amylase was inactivated by TP in ways of complexation and modification of secondary conformations.     

Quality identification and evaluation of Pu‐erh teas of different grade levels and various ages through sensory evaluation and instrumental analysis

To develop an objective, effective, flexible and cost‐saving method to assess Pu‐erh tea quality, Pu‐erh tea samples of different grade levels and various ages were analysed using sensory evaluation and various instrumental techniques, including chemical analysis and electronic tongue (ET). Results showed that taste profile analysis as a sensory evaluation method can meticulously describe and distinguish different Pu‐erh tea samples. Chemical analysis combined with hierarchical cluster analysis can cluster Pu‐erh ripened and raw tea both in compressed and scattered forms. However, no obvious variation tendency was observed in the chemical composition parameters of Pu‐erh tea of different grade levels or various ages. ET combined with principal components analysis (PCA) is effective in classifying Pu‐erh tea samples of different grade levels and various ages. ET followed by linear discriminant analysis (LDA) performs well in identifying Pu‐erh tea samples of various ages by establishing a discriminant model.     

Production of yellow wine from Camellia Oleifera meal pretreated by mixed cultured solid‐state fermentation

Camellia oleifera meal was evaluated to be a potential feedstock for the production of yellow wine (YW), and process conditions were investigated. In this study, C. oleifera meal was firstly pretreated using mixed cultured Bacillus subtilis and Aspergillus niger under solid‐substrate fermentation to degrade the tea saponin (TS) for the following YW fermentation. Response surface methodology helped evaluate the effects of the selected operating parameters, and the optimal condition at a fixed time of 4 days, which gave a 67.84 ± 0.23% degradation rate of TS, was reached as inoculum concentration of 16%, initial moisture content of 55% and temperature of 30 °C. Finally, 7‐day fermentation was harvested to be the most suitable pretreatment for producing YW from C. oleifera meal, and the twice‐feeding fermentation for YW was obtained as wheat koji 12% and active yeast 1.2%. In addition, ample amino acids, phenolic components and the trace TS endowed the C. oleifera wine, the more nutritional characteristics.     

Quantification of 1,8‐cineole and of its metabolites in humans using stable isotope dilution assays

The metabolism of 1,8‐cineole after ingestion of sage tea was studied. After application of the tea, the metabolites 2‐hydroxy‐1,8‐cineole, 3‐hydroxy‐1,8‐cineole, 9‐hydroxy‐1,8‐cineole and, for the first time in humans, 7‐hydroxy‐1,8‐cineole were identified in plasma and urine of one volunteer. For quantitation of these metabolites and the parent compound, stable isotope dilution assays were developed after synthesis of [²H₃]‐1,8‐cineole, [9/10‐²H₃]‐2‐hydroxy‐1,8‐cineole and [¹³C,²H₂]‐9‐hydroxy‐1,8‐cineole as internal standards. Using these standards, we quantified 1,8‐cineole by solid phase microextraction GC‐MS and the hydroxyl‐1,8‐cineoles by LC‐MS/MS after deconjugation in blood and urine of the volunteer. After consumption of 1.02 mg 1,8‐cineole (19 μg/kg bw), the hydroxycineoles along with their parent compound were detectable in the blood plasma of the volunteer under study after liberation from their glucuronides with 2‐hydroxycineole being the predominant metabolite at a maximum plasma concentration of 86 nmol/L followed by the 9‐hydroxy isomer at a maximum plasma concentration of 33 nmol/L. The parent compound 1,8‐cineole showed a low maximum plasma concentration of 19 nmol/L. In urine, 2‐hydroxycineole also showed highest contents followed by its 9‐isomer. Summing up the urinary excretion over 10 h, 2‐hydroxycineole, the 9‐isomer, the 3‐isomer and the 7‐isomer accounted for 20.9, 17.2, 10.6 and 3.8% of the cineole dose, respectively.     

Critical parameters in cost-effective alkaline extraction for high protein yield from leaves

Leaves are potential resources for feed or food, but their applications are limited due to a high proportion of insoluble protein and inefficient processing. To overcome these problems, parameters of alkaline extraction were evaluated using green tea residue (GTR). Protein extraction could be maximized to 95% of total protein, and, after precipitation by pH adjustment to 3.5, 85% of extracted protein was recovered with a purity of 52%. Temperature, NaOH amount, and extraction time are the protein yield determining parameters, while pH and volume of extraction liquid are critical parameters for production cost. The cost of energy and chemicals for producing 1 t GTR proteins is minimized to 102€, and its nutritional value is comparable to soybean protein. Furthermore, this technology was successfully applied to other sources of biomass and has potential to be used as a part of an integrated bio-refinery process.     

Addition of phytochemical-rich plant extracts mitigate the antimicrobial activity of essential oil/wine mixtures against Escherichia coli O157:H7 but not against Salmonella enterica

Marinades for preparing raw meats for cooking are frequently made of wine and herbs. We simulated several formulations of potential antimicrobial marinades with these components and other food compatible/food derived extracts. Red wine formulations containing essential oils from oregano or thyme, or their primary active components carvacrol and thymol, respectively, and a mixture of plant extract powders from phytochemical-rich apple skin, green tea, and olive, were evaluated for inhibitory activity against the foodborne pathogens Escherichia coli O157:H7 and Salmonella enterica. Red wine alone exhibited low activity, as did the plant extract suspended in the wine. Surprisingly, the high activity of oregano or thyme essential oils in red wine was reduced in E. coli, but not in Salmonella, by addition of the plant extract. This study shows that essential oils in red wine can be an effective antimicrobial in food, however the possibility exists that phytochemicals, added to the treatment solution or natively present in the food itself, could adversely impact the antimicrobial activity and should be addressed with future studies.     

Quantitation of estragole by stable isotope dilution assays

Various calibration strategies for the quantitation of the phenylpropane estragole by gas chromatography-mass spectrometry were developed and compared. For application in stable isotope dilution assays, two deuterium labelled estragole isotopologues were synthesized. Of these, [3′,3′-²H₂]estragole was prepared by Wittig reaction of 4-methoxy-phenylacetaldehyde with [²H₃]methyl-triphenyl-phosphonium bromide, whereas [1″,1″,1″-²H₃]estragole was obtained by demethylation of estragole and deuteromethylation of the resulting 4-allylphenole.Besides estragole isotopologues, 1,2,4-trimethoxybenzene and 4-propylanisole were also tested as internal standards (I.S.) for the determination of estragole in fennel tea.[1″,1″,1″-²H₃]Estragole, 1,2,4-trimethoxybenzene, and 4-propylanisole revealed linear calibration functions and, therefore, were suitable for estragole quantitation. In contrast to this, [3′,3′-²H₂]estragole could only be applied as I.S. if it was added to the extracts in stoichiometric deficiency compared to unlabelled estragole. Moreover, due to its different chemical and physical properties, 1,2,4-trimethoxybenzene showed a recovery as low as 77%, whereas the other I.S. revealed recovery rates close to 100%. Considering the “real” values of estragole in fennel tea, the choice of the I.S. obviously is less important than the way of preparing the tea. In contrast to the common method for tea preparation, squeezing of the teabags increased the estragole content significantly by 50%.