In-vitro studies on the effect of polyphenol oxidase and peroxidase on the formation of polyphenolic black tea constituents

Flavanols (catechins and gallocatechins) isolated from green tea leaves (Camellia sinensis) (L) O Kuntze) were treated in vitro with polyphenol oxidase, peroxidase and a combination of both. The flavanol levels and those of the products formed were monitored by reversed-phase high-performance liquid chromatography (HPLC using spectrophotometric detection at 280 and 380 nm. Flavanols and theaflavins were quantified, whilst integrated peak areas are given for the remaining compounds. After fermentation in the presence of polyphenol oxidase higher levels of theaflavins and resolved thearubigins were obtained, whilst peroxidase produced higher amounts of chromatographically unresolved thearubigins of higher molecular weight, observed as a rise in the HPLC baseline, in the presence of peroxidase a significant decrease in the levels of all flavonol glycosides was observed, whilst in the presence of polyphenol oxidase only myricetin glycoside levels decreased.     

Gaschromatographisch-massenspektrometrische Untersuchungen zur Kinetik der Redoxreaktionen vonl -Ascorbins?ure undl -Dehydroascorbins?ure in Weizenmehlteigen

Summary A gaschromatographic/mass spectrometric method for separation and determination ofl-ascorbic acid (l-AA) and the different isomeric forms ofl-dehydro ascorbic acid (l-DAA) and 2,3-diketogulonic acid (l-DKG) in wheat doughs is described. Doughs with addedl-AA resp.l-DAA were included in the investigation. In all doughs thel-DAA was in its monomeric 3,6-anhydro-2-hydrate form. 2,3-DKG was not detectable.[/p]We confirm recent statements in the literature about the kinetics of the oxidation ofl-AA tol-DAA in doughs with addedl-AA. The loss of total ascorbic acid (l-AA+l-DAA) after dough making was approx. 30%. Only a small quantity ofl-AA was formed in doughs upon addition ofl-DAA. In this case the loss of total ascorbic acid was approx. 70%.[/p]From that and from investigations on doughs with 14C-labeledl-AA and measurements of the available thiol groups in doughs we conclude thatl-AA/l-DAA at least partially doesn't react like a redox system but thatl-DAA forms intermolecular condensation products with amino groups of proteins. These may contribute to improved baking quality.Zusammenfassung Es wird eine gaschromatographisch-massenspektrometrische Methode beschrieben, mit derl-Ascorbinsäure (l-AS) und die verschiedenen isomeren Formen derl-Dehydroascorbinsäure (l-DAS) und der 2,3-Diketogulonsdure (2,3-DKG) in Weizenmehlteigen getrennt und quantitativ bestimmt werden können. Teige mit Zusatz vonl-AS bzw.l-DAS wurden analysiert. Die L-DAS lag in allen Fällen in der monomeren bicyclischen 3,6-Anhydro-2-Hydrat-Form vor; 2,3-DKG war nicht nachweisbar. Bei Teigen mit Zusatz vonl-AS konnten die Angaben der Literatur über die Kinetik der Oxidation derl-AS zurl-DAS bestätigt werden. Der Verlust an Gesamtascorbinsäure (l-AS +l-DAS) lag nach dem Anteigen bei ca. 30%. In Teigen mit Zusatz vonl-DAS wurde nur wenigl-AS gebildet, der Verlust an Gesamtascorbinsäure lag in diesem Fall bei ca. 70%. Hieraus und aus Untersuchungen an Teigen mit 14C-markierterl-AS und Messungen des verfügbaren Thiolgehalts in Teigen schließen wir, dal-AS/l-DAS zumindest teilweise nicht als Redoxsystem reagiert, sondern daß diel-DAS mit Aminogruppen der Proteine intermolekulare Kondensationsprodukte bildet, die zur backverbessernden Wirkung beitragen dürften.[/p]     

Absolute measurement of F2-laser power at 157 nm

We report a comparison of laser power measurements at the F2-laser wavelength of 157 nm made at two facilities of the Physikalisch-Technische Bundesanstalt (PTB), the German national metrology institute. At the PTB laboratory at the electron storage ring BESSY II in Berlin, the scale for laser power was directly traced to a cryogenic radiometer operating at 157 nm, whereas at the PTB laser radiometry facility in Braunschweig the calibration of transfer detectors was performed with a newly developed standard for laser power at 157 nm, which is traceable in several steps to a cryogenic radiometer operating at 633 nm. The comparison was performed under vacuum conditions with laser pulse energies of approximately 10 microJ, however with different average powers because different primary standard radiometers were used. The relative deviation for the responsivity of the transfer detector was 4.8% and thus within the combined standard uncertainty.     

Radon im Grundwasser des Mühlviertels (Oberösterreich)

In the occurrence areas of selected crystalline rocks—mainly granites—the Radon-222 content of groundwater has been investigated. The results show a significant correlation with the Uranium concentrations in the rocks. The Uranium concentrations were between 1 and 15 ppm, while the Radon-222 concentrations were between 0.2 and 719.5 Bq/l. To identify Radon-decreasing effects like degasification and admixture of surface water, CO₂ partial pressures and Oxygen-18 in water samples were determined and the local hydrological situation has been taken under consideration. Samples which showed clear evidence of Radon-decreasing effects were excluded from further evaluation because they would not represent the full empiric potential of Radon emanation in the aquifer. In combination with geological maps, petrologic information and airborne radiometry, Radon-222 analyses in groundwater can provide important data for Radon potential mapping. The significance of the groundwater Radon analyses can be improved by supplementary hydrochemical and hydrological isotope investigations.     

Polystyrol‐Extruderschaum mit verbesserten wärmetechnischen Eigenschaften — Entwicklung,Prüfung und Anwendung

Ein neuer Wärmedämmstoff aus extrudiertem Polystyrol‐Hartschaum (XPS) mit geringerer Wärmeleitfähigkeit wurde entwickelt, um die erhöhten Anforderungen an einen dauerhaften Wärmeschutz von Gebäuden einfacher und mit geringerem Materialaufwand zu erfüllen. Die bewährten mechanischen und hygrothermischen Eigenschaften von XPS‐Dämmstoffen werden beibehalten. Die erste Produkt‐Generation ist insbesondere für die außenliegende Wärmedämmung von erdberührten Wänden und Böden sowie für die Kerndämmung von zweischaligen Wänden entwickelt worden. Das verwendete CO₂‐Schäumverfahren entspricht den bestehenden Anforderungen an die Nachhaltigkeit von Bauprodukten. Development, testing and application of extruded polystyrene foam (XPS) insulation with improved thermal properties. Improved extruded polystyrene foam (XPS) insulation with lower thermal conductivity has been developed. This enables meeting the increased requirements for sustainable building insulation with better material efficiency. The proven mechanical and hygro‐thermal properties of XPS insulation are maintained. This first product generation has been developed primarily for external perimeter insulation of basement walls and floors as well as for the insulation of cavity walls. The CO₂ foaming technology meets the sustainability requirements for building products.     

Expression of fatty acyl-CoA binding proteins in colon cells: response to butyrate and transformation

Fatty acyl-CoA affect many cellular functions as well as serving as cellular building blocks. Several families of cytosolic fatty acyl-CoA binding proteins may modulate the activities of fatty acyl-CoA. Intestinal enterocytes contain at least three unique families of cytosolic proteins that bind fatty acyl-CoA: acyl-CoA binding protein (ACBP), fatty acid binding proteins (including the liver, L-FABP and intestinal, I-FABP), and sterol carrier protein-2 (SCP-2). Immortalized rat colon epithelial cell lines expressed only ACBP and SCP-2 at levels of 0.75±0.13 and 0.42±0.02 ng/μg protein. Ras and src transformation increased colon cell density and differentially altered ACBP and SCP-2 expression without affecting I-FABP or L-FABP levels. ACBP levels were 1.8-fold and 1.5-fold increased in ras- and src-transformed cells, respectively. In contrast, SCP-2 expression was significantly decreased 55 and 67% in ras- and src-transformed cells, respectively. Butyrate treatment of ras- and src-transformed cells decreased cell proliferation up to 60–85% as compared to 25–30% in control cells. Butyrate treatment decreased ACBP expression in all cell lines but had no effect on the levels of SCP-2, I-FABP, or L-FABP. These studies suggest that the differential expression of ACBP and SCP-2 in rat colonic cell lines, as well as their modulation by butyrate, may be altered by cell transformation.     

Tragverhalten von Stahlbetonbalken bei geneigter Querkraft

Bearing Behaviour of RC Beams Subjected to Biaxial Shear Forces The shear bearing behaviour of RC beams is still subject of expert's discussion and intensive research. Most investigations focus on uniaxial loading conditions parallel to one principal axis. More recently, biaxial shear – leading to inclined shear forces – was theoretically considered and integrated into new design concepts. However, its experimental basis is rather limited. Thus, extensive biaxial shear tests are carried out and analysed. Their main findings are presented in the paper. The design concept is elaborated to introduce inclination effects into all partitions of the resistances provided by the tensile and the compressive shear struts. Designs become more precise and more economic.