Investigation on the extractability of melanoidins in portioned espresso coffee

Coffee melanoidins have attracted interest as a result of its potential health benefits. This investigation aims to elucidate the extraction behavior of melanoidins and their populations during the preparation of portioned espresso coffee and its relationship with the antioxidant activity of the coffee brew. Filter-paper pods, FAP capsule, and clone capsule containing light roasted coffee have been investigated. An accumulative fractionation approach has applied to model the extraction kinetics of melanoidins, melanoidin populations, browning, chlorogenic acids (CGA), and antioxidant activity. Melanoidins were very efficiently extracted in clone capsules since less than 9 s was necessary to extract the 50% of the melanoidin content as compared with pods and FAP capsules, and the kinetic of extraction is slower than CGA. The extraction profile of melanoidins and browning fitted better with the antioxidant capacity than CGA and total solids profile. Melanoidin populations were obtained according to ethanol solubility. Total melanoidin content and the ratio between melanoidin populations did not change during extraction volume for espresso coffee. Melanoidin populations soluble at 75% ethanol showed the highest antioxidant activity. However, melanoidins with higher antioxidant activity are extracted at higher volumes. This investigation could make possible the adjustment of the technological requirements of espresso coffeemakers to produce an espresso coffee with high levels of beneficial compounds.     

Entwicklung eines optisch zugänglichen Reaktors zur Thermographiemessung in einer Katalysatorschüttung

To measure the microkinetics in heterogeneously catalyzed strongly exothermic gas phase reaction heat and mass transfer limitations should be excluded. Also an unequal distribution of temperature in the catalyst fixed bed, like a hot spot, distorts the results of microkinetic investigations. A promising approach to measure the temperature contactless is thermography. For this work, an optically accessible reactor is developed to measure the temperature in a catalytically powder fixed bed. In the scope of this work, this technique is used to investigate the temperature development and distribution during the exothermal CO₂ methanation depending on the bed and gas dilution and the reactor performance.     

Activity and Tissue Expression of Tyrosine Phosphatase PTP-MEG2

Protein tyrosine phosphatases(PTPs) are crucial regulators of signal transduction. Among them,PTP-MEG2 is an intracellular enzyme of 593 amino acid residues with a putative lipid-binding domain at the N-terminus. In the present study, we cloned the full-length form of the enzyme and expressed it in E. coli cells as a 6xHis-tagged protein. The majority of the expressed enzyme was found in the inclusion body of E. coli cell extracts.Upon extraction with a buffer containing urea, the recombinant enzyme was purified to near homogeneity on a single Ni-NTA-agarose column. This procedure resulted in the production of over 100 mg of purified recombinant PTP-MEG2 from 1 L E. coli cell culture. The purified protein displayed a single polypeptide band with expected molecular size on SDS-polyacrylamide gel electrophoresis under reducing conditions. Isolated under denatured conditions in urea, the purified enzyme was re-natured by dialyzing against a refolding buffer. The re-natured enzyme effectively dephosphorylated the common PTP substrate para-nitrophenylphosphate with a specific activity of 2000units/mg. Meanwhile, the denatured enzyme was used to immunize a rabbit to produce antibodies. The resulting antiserum had extremely high sensitivity and specificity. When used for Western blot analysis, the anti-serum revealed a wide expression of PTP-MEG2 in many tissues of mice. Together, we developed a highly effective way to purify a large amount of PTP-MEG2 and generated highly sensitive antibodies that can specifically detect endogenous expression of the enzyme in tissues.     

Design,experimental investigation and multi-objective optimization of a small-scale radial compressor for heat pump applications

The main driver for small scale turbomachinery in domestic heat pumps is the potential for reaching higher efficiencies than volumetric compressors currently used and the potential for making the compressor oil-free, bearing a considerable advantage in the design of advanced multi-stage heat pump cycles. An appropriate turbocompressor for driving domestic heat pumps with a high temperature lift requires the ability to operate on a wide range of pressure ratios and mass flows, confronting the designer with the necessity of a compromise between range and efficiency. The present publication shows a possible way to deal with that difficulty, by coupling an appropriate modeling tool to a multi-objective optimizer. The optimizer manages to fit the compressor design into the possible specifications field while keeping the high efficiency on a wide operational range. The 1D-tool used for the compressor stage modeling has been validated by experimentally testing an initial impeller design. The excellent experimental results, the agreement with the model and the linking of the model to a multi-objective optimizer will allow to design radial compressor stages managing to fit the wide operational range of domestic heat pumps while keeping the high efficiency level.     

Profiles,antioxidative and ACE inhibitory activity of peptides released from fermented buttermilk before and after simulated gastrointestinal digestion

Bioactive peptides, released from buttermilk by fermentation and/or gastrointestinal proteases, may have health promoting effects. Thus, a comprehensive analysis of the peptide fraction of fermented buttermilk, before and after different phases of simulated gastrointestinal digestion, was performed using ultra high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UHPLC-ESI-MS/MS). Results showed that digestion simulation substantially changed the peptide profile of fermented buttermilk. A total of 81, 120 and 46 peptides were identified in fermented buttermilk, its gastric and intestinal digests, respectively. These peptides released mostly from β-casein followed by αs1-casein, κ-casein and β-lactoglobulin. In addition, 14 peptides released from milk fat globule membrane proteins (lactadherin, butyrophilin and GlyCAM-1). Bioactivity, mainly angiotensin converting enzyme (ACE) inhibitory activity, has been reported before for only 54 of the detected peptides. Radical scavenging, ferric reducing and ACE inhibitory activities of fermented buttermilk peptides increased significantly after digestion, indicating promotion in fermented buttermilk-peptide bioactivity by gastrointestinal digestion.     

Sensory characteristics and volatile components in aromas of boiled prawns prepared according to experimental designs

Comparing samples prepared according to a two-level fractional-factorial design, parts of prawns and pH were selected as essential factors for generating boiled prawn aroma. Aroma characteristics in samples prepared based on a three-level full-factorial design for pH (2, 7, and 12) and parts (shell: S, meat: M, and meat with shell: W) were quantitatively described using 10 attributes. “Sweet”, “cooked fish”, “roasted shrimp” and “boiled prawn” scores were higher in M and W samples at pH 7, but “sewage” scores were higher in all S samples. Response surfaces in statistically significant models obtained for seven attributes clearly visualized how parts and pH influenced them. Partial least squares regression models composed of selected influential peaks for seven attributes were highly predictable.     

植筋胶拉伸抗剪本构关系的研究

通过对钢筋与金属套筒之间采用植筋胶粘结的拉伸抗剪试验，探讨了植筋胶的粘结机理和拉伸抗剪破坏模式。在对试验结果综合分析的基础上，提出了植筋胶拉伸抗剪粘结滑移本构关系的三段式模型，为植筋锚固有限元分析提供了必要的基础。     

Stabilization of air bubbles in oil by surfactant crystals: A route to produce air-in-oil foams and air-in-oil-in-water emulsions

The incorporation of air in vegetable oils is highly sought after as it allows reducing the total fat content, while providing a light and pleasant texture. To meet consumers' requirements, nonaqueous foams must remain kinetically stable for several months and must withstand large deformations and flows. In this paper, we describe the fabrication of air-in-oil foams of outstanding stability, both at rest and under flow, based on the use of crystallizable surfactants (mixture of mono- and diglycerides). The air volume fraction is close to 55%, irrespective of the surfactant concentration. The air bubbles are protected against coalescence and Ostwald ripening by a dense layer of crystals. Moreover, the firmness of the surfactant crystal network formed in the oil bulk is large enough to hinder buoyancy driven phenomena. Finally, we demonstrate that the oil foams can be dispersed in an aqueous phase containing hydrocolloids to form a novel type of material: air-in-oil-in-water (A/O/W) emulsions.     

Human sweat odour conjugates in human milk,colostrum and amniotic fluid

Using ultra performance liquid chromatography–mass spectrometry we identified for the first time glutamine-N-α-conjugates of the fatty acids (E)/(Z)-3-methylhex-2-enoic acid and (R)/(S)-3-hydroxy-3-methylhexanoic acid as well as cysteinylglycine-S-conjugates of (R)/(S)-3-methyl-3-sulphanylhexan-1-ol and (R)/(S)-3-sulphanylhexan-1-ol as constituents of human milk and colostrum. The glutamine-N-α-conjugates were detected also in human amniotic fluids. The mean values of glutamine-N-α-conjugate of (R)/(S)-3-hydroxy-3-methylhexanoic acid were highest in colostrums with a range of <0.1–382 μg/kg, followed by the mature human milk with values from <0.1 to 39.6 μg/kg for defatted milk, and 0.8–7.0 μg/kg in amniotic fluids. The cysteinylglycine-S-conjugate of (R)/(S)-3-methyl-3-sulphanylhexan-1-ol were detected in the range of 2–24 ng/kg in human milk, and 7–101 ng/kg in colostrums. Our data demonstrate that concentrations in human milk vary between individuals, and with lactation period as the mean concentrations of the glutamine conjugates in colostrums were elevated in comparison to mature milk and the concentrations of acid precursors were close to 10 times higher. Further, these precursors were not detected in cow milk.     

The determination of the caffeic acid derivatives of Echinacea purpurea aerial parts under various extraction conditions by supercritical fluid extraction (SFE)

The effects of various process conditions on the extraction of caffeic acid derivatives (CADs) from the aerial parts of Echinacea purpurea specimens grown in Turkey through supercritical fluid extraction (SFE) and two conventional techniques (ultrasound and shaker) were determined by LC–MS/MS. The concentrations of caftaric acid, cichoric acid, chlorogenic acid, cynarin, and echinacoside were measured. Three extraction variables, i.e., the extraction pressure (EP; 100, 200, and 300 bar), the extraction temperature (ET; 40, 50, and 60 °C), and the amount of MeOH used as co-solvent (CL; 0%, 5%, and 10%, m/m), were investigated. The ultrasound-assisted extraction exerted more influence on the CADs concentrations than the shaker extraction. Moreover, the effects of the EP*ET and the EP*CL interactions on the SFE extract yield (0.09–0.87%, m/m) and the effect of EP*ET*CL interaction on the individual and total CADs concentrations were identified (p < 0.05).