Characterisation of Aronia powders obtained by different drying processes

Nowadays, food industry is facing challenges connected with the preservation of the highest possible quality of fruit products obtained after processing. Attention has been drawn to Aronia fruits due to numerous health promoting properties of their products. However, processing of Aronia, like other berries, leads to difficulties that stem from the preparation process, as well as changes in the composition of bioactive compounds. Consequently, in this study, Aronia commercial juice was subjected to different drying techniques: spray drying, freeze drying and vacuum drying with the temperature range of 40–80 °C. All powders obtained had a high content of total polyphenols. Powders gained by spray drying had the highest values which corresponded to a high content of total flavonoids, total monomeric anthocyanins, cyaniding-3-glucoside and total proanthocyanidins. Analysis of the results exhibited a correlation between selected bioactive compounds and their antioxidant capacity. In conclusion, drying techniques have an impact on selected quality parameters, and different drying techniques cause changes in the content of bioactives analysed. Spray drying can be recommended for preservation of bioactives in Aronia products. Powder quality depends mainly on the process applied and parameters chosen. Therefore, Aronia powders production should be adapted to the requirements and design of the final product.     

Spatial distributions of O2, CO2 and SO2 in a pilot-scale fluidized bed combustor operated with different coals

Axial concentration profiles of O₂, CO₂ and SO₂ have been measured at different radial positions in a coal-fired fluidized bed combustor. The profiles show some spatial inhomogeneity in the bed, the degree of which depends on fluidizing velocity and amount of excess air. Comparison of SO₂- with CO₂-concentration profiles reveals that SO₂ is formed in proportion to CO₂ only with anthracite as fuel. With bituminous coals, SO₂ is preferentially formed near the coal feed point. These results are discussed with regard to characteristic times of mixing and chemical reaction in fluidized beds, and SO₂-formation characteristics of the employed coals obtained in a thermobalance.     

Separation of stat-copoly(styrene/2-methoxyethyl methacrylate) samples according to composition by gradient high-performance liquid chromatography

Statistical copolymers of styrene (S) and 2-methoxyethyl methacrylate (MEMA) (13–87 mass % of the latter monomer) were investigated by gradient HPLC on columns with either silica or CN-bonded phase packings. The samples were injected in THF solution. The starting eluent was in each case a nonsolvent (isooctane or mixtures of isooctane with THF and methanol). Separation was achieved by increasing the concentration of THF or methanol in the eluent. A calibration mixture of four copolymers (26, 49, 62, and 87% MEMA) was investigated according to the principles of chromatographic cross-fractionation (CCF) by size exclusion chromatography and subsequent gradient HPLC. The influence of molar mass on HPLC retention was small and, for the samples investigated by CCF, independent of copolymer composition. The composition effect on detector signal was also studied. At 230 nm wavelength and with MEMA content in the range between 20 and 40%, the effect was small and caused the average composition calculated from CCF results to deviate from the directly measured value by not more than 0.2 or 0.8% for the two copolymers investigated.     

Praxisorientierte Raffination von Stahlschmelzen mit Seltenerdmetallen

Simulation eines pfannenmetallurgischen Stahlraffinationsverfahrens unter Verwendung von Cer-Mischmetall, einer Raffinationsschlacke und Argonspülung zur Reinheitsgradverbesserung. Darstellung typischer nichtmetallischer Einschlüsse. Aufzeigen der erzielten Zähigkeitsverbesserungen und der Verringerung der Zähigkeitsanisotropie.     

Characterization of laser-beam surface treated cold and hot working steels

In order to increase the wear resistance of metal forming tools, four different cold and hot working steels were laser-beam surface melted and alloyed with titanium carbide and vanadium carbide. The layers were investigated concerning chemical composition, microstructure, hardness profiles, wear behaviour measured by pin-on-disk-tests with different counterbodies and plastic behaviour of the surface by a new developed repeated impact testing machine. It turned out to be more useful to take a substrate which is already quenched and tempered prior to the laser-beam surface treatment than to carry out the tool hardening heat treatment afterwards. A tempering step after the laser-beam alloying offers the advantage of carbide precipitates in the layer connected with an increase in the hardness and a reduction of residual stresses. By means of laser-beam surface alloying the wear protection of the layer can be increased while the alloying content of the substrate is reduced with respect to the core fracture toughness. The optimal alloying addition depends on the demands of the envisaged application.     

Festigkeitsänderungen bei verschiedenen Verformungsarten

Bestimmung von Streckgrenze und Zugfestigkeit beim Ziehen und Walzen von Stahldrähten mit Kohlenstoffgehalten zwischen 0,006 und 0,6%. Einfluß des Wechsels der Verformungsart vom Ziehen zum Walzen auf den weiteren Anstieg der Festigkeitswerte. Anfänglicher Abfall der Festigkeitswerte vor allem bei patentierten Stahldrähten mit höherem Kohlenstoffgehalt. Deutung des Festigkeitsabfalles als Zerstörung der bei der Verformung aufgetretenen Alterung und Änderung der gerichteten Eigenspannungen zwischen den verschiedenen Phasen.     

Ermittlung von gelöstem Kohlenstoff und Stickstoff mit einem Torsionspendel für streifenförmige Proben

Beschreibung eines Torsionspendels zur Messung der Dämpfung und Ermittlung des Gehaltes an gelöstem Kohlenstoff und Stickstoff an streifenförmigen Proben mit niedrigen Gehalten an interstitiell gelösten Elementen. Messung der Dämpfung bei Eisen-Kohlenstoff-, Eisen-Stickstoff- und Eisen-Kohlenstoff-Stickstoff-Legierungen ohne und mit Mangan. Darstellung der rechnerischen Ermittlung von Kohlenstoff und Stickstoff bei gleichzeitigem Vorliegen beider Elemente.     

Einfluß der Probengeometrie auf die Ergebnisse von Bruchmechanik-Untersuchungen an dem Stahl StE 47

Untersuchung an Kompakt-Zug-(CT-)Proben zum Einfluß der Probendicke und -breite auf die Rißzähigkeit des Stahls StE 47 in Abhängigkeit von der Prüftemperatur. Auswirkungen auf die Ausbildung der plastischen Zone und das Bruchaussehen. Vergleich der Rißzähigkeit mit den bruchmechanischen Kenngrößen Rißaufweitung und J-Integral.