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排序方式: 共有461条查询结果,搜索用时 15 毫秒
91.
Lina Mayuoni-kirshinbaum Zipora Tietel Ron Porat Detlef Ulrich 《European Food Research and Technology》2012,235(2):277-283
During the last few years, there has been a tremendous increase in consumption of pomegranate fruit and juice. Nevertheless, very little is yet known regarding the volatile constituents that determine the unique aroma of pomegranate fruit. We extracted aroma volatiles from fresh ‘Wonderful’ pomegranate juice using solvent-assisted flavour evaporation (SAFE) and headspace solid-phase micro-extraction (HS-SPME) methods, and applied gas chromatography–olfactometry (GC–O) (‘sniffing’) combined with gas chromatography–mass spectrometry (GC–MS) analysis, in order to identify volatile aroma-active compounds. In addition, we performed stir bar sorptive extraction (SBSE) of pomegranate aroma volatiles, coupled with GC–MS analysis, in order to assist in identifying aroma-active compounds. Overall, we tentatively identified 23 volatiles in the SAFE and HS-SPME extracts; they belonged to various chemical classes, including aldehydes, terpenes, alcohols, esters, furans and acids. Using the GC–O nasal impact frequency method, we tentatively detected 12 aroma-active peaks and identified the corresponding odourants by GC–MS. The aroma-active compounds of ‘Wonderful’ pomegranates were ethyl-2-methylbutanoate (fruity, apple), hexanal (green), β-pinene (pine, herbal), β-myrecene (woody, musty), cis-3-hexenal (green), limonene (fruity, musty), cis-2-heptenal (soapy, mushroom), cis-3-hexenol (earthy, grassy), 2-ethylhexanol (floral), β-caryophyllene (fruity, musty), 2(5H)-furanone (sweet, fruity) and β-sesquiphellandrene (terpene, almond). Overall, the flavour of ‘Wonderful’ pomegranate fruit derives from a mixture of various ‘green’, ‘woody’, ‘earthy’, ‘fruity’, ‘floral’, ‘sweet’ and ‘musty’ notes. 相似文献
92.
Susanne?K?gelEmail author Jürgen?Gross Christoph?Hoffmann Detlef?Ulrich 《European Food Research and Technology》2012,234(3):399-404
The study focuses on the odor-active intensity and occurrence of three methoxypyrazines in ladybird beetles, Harmonia axyridis, invasive in Europe and the USA, and Coccinella septempunctata, native in Europe, but invasive in the USA. It is known from previous studies that H. axyridis has negatively influenced the taste of wine in the USA because of releasing their hemolymph in must during harvesting. In
relation to C. septempunctata, H. axyridis had more nitrogen containing compounds in its hemolymph and 2-isopropyl-3-methoxypyrazine (IPMP) and mainly 2-sec-buthyl-3-methoxypyrazine
(SBMP) in higher amounts. The compound IPMP was detected as the main odor-active compound in both ladybird beetle species.
Wines infested with hemolymph of C. septempunctata were more readily detected as altered wine with a ‘ladybird taint’ than wines infested with H. axyridis. 2-isobuthyl-3-methoxypyrazine (IBMP) could be identified as second intensive odor-active compound of C. septempunctata, which occurred in a much lower frequency in H. axyridis. SBMP, the second highest measured N-compound of H. axyridis, had a lower olfactory active threshold in gas chromatography–olfactometry test. C. septempunctata contained less SBMP in its hemolymph than H. axyridis. This study objected that besides H. axyridis also C. septempunctata can influence the taste of wine in a detectable way. 相似文献
93.
Detlef Ulrich Adolf Rapp und Edelgard Hoberg 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1995,200(3):217-220
Zusammenfassung Die flüchtigen Aromakomponenten von dreizehn Kulturerdbeersorten und von Walderdbeeren wurden im Freon-Extrakt von frischen und gefrosteten Früchten untersucht. Mit Hilfe der GC/MS konnten etwa 120 flüchtige Verbindungen identifiziert werden. Über eine Aromaextrakt-Verdünnungsanalyse (AEVA) erfolgte mittels Schnüffeltechnik die Bestimmung der wesentlichen sensorischen Qualitäten, denen 17 Schlüsselverbindungen zugeordnet werden konnten. Die Analyse der Schlüsselverbindungen im Erdbeersortiment zeigt deutliche Sortenunterschiede.
Analysis of strawberry flavour — Quantification of the volatile components of varieties of cultivated and wild strawberries
The volatile components of thirteen strawberry varieties and of a wild strawberry were evaluated in the freon-extract of fresh and frozen fruits. With the aid of GC/MS about 120 volatile substances could be identified. The determination of the substantial sensory qualities resulted from AEDA with sniffing technique. In this way 17 key compounds could be attached. The analysis of the key compounds point out significient variety differences.相似文献
94.
Luisa Whittaker-Brooks Jeffrey M. Mativetsky Arthur Woll Detlef Smilgies Yueh-Lin Loo 《Organic Electronics》2013,14(12):3477-3483
We investigated the characteristics of inverted solar cells comprising bulk-heterojunction active layers of ZnO nanowire arrays and poly(3-hexylthiophene), P3HT. By utilizing a sputtered ZnO seed layer, we are able to grow vertically oriented ZnO nanowire arrays homoepitaxially. Unlike the ZnO nanowires that are grown on sol–gel derived seed layers, our nanowires are more uniform in their dimensions and spatial distribution. This sputtered seed layer also acts as the hole-blocking layer when these nanowire arrays are incorporated in solar cells; hybrid solar cells comprising these nanowires and P3HT exhibit power conversion efficiencies of 1.6%. To date, this is the highest efficiency observed for ZnO nanowire arrays:P3HT hybrid solar cells. 相似文献
95.
Joachim Pasel Remzi Can Samsun Ralf Peters Björn Thiele Detlef Stolten 《International Journal of Hydrogen Energy》2014
The long-term stability at autothermal reforming of diesel fuel and kerosene was studied using Juelich's autothermal reformer ATR 9.2, which is equipped with a commercial proprietary RhPt/Al2O3–CeO2 catalyst. The experiment was run for 10,000 h of time on stream at constant reaction conditions with an O2/C molar ratio of 0.47, a H2O/C molar ratio of 1.9, and a gas hourly space velocity of 30,000 h−1. Kerosene produced via the gas-to-liquid process and diesel fuel synthesized via the bio-to-liquid route were used. Both fuels were almost free of mass fractions of sulfur and aromatics. The trends for the desired main products of autothermal reforming H2, CO, CO2, and CH4 were almost stable when kerosene was used. When the fuel mass flow was switched to diesel fuel however, different modes of catalyst deactivation occurred (active sites blocked by carbonaceous deposits, sintering processes), leading to a decrease in the concentrations of H2 and CO2 with a simultaneous increase in the CO content. This paper defines carbon conversion as the decisive criterion for evaluating the long-term stability during autothermal reforming of kerosene and diesel fuel. Carbon conversion was diminished via three different pathways during the long-term experiment. Undesired byproducts found in the gas phase leaving the reactor had the strongest impact on carbon conversion. These byproducts included ethene, propene, and benzene. Furthermore, a liquid oily residue was detected floating on the condensed unconverted mass flow of water. This happened once during the whole experiment. Finally, undesired organic byproducts were dissolved in the mass flow of unconverted water. These were found to be straight-chain and branched paraffins, esters, alcohols, acids, aldehydes, ketones, etc. Nevertheless, at the end of the long-term experiment, carbon conversion still amounted to more than 98.2%. 相似文献
96.
97.
98.
Detlef Dormagen 《国际钢铁研究》1988,59(8):368-374
The development of steel grade up to X 80 quality was shown explaining metallurgical mechanisms used for thermomechanically rolled steels with improved toughness behaviour. The influence of the reduction of C-content for these TM-steels on the field welding behaviour was discussed. The development of steels with improved resistance against sour media was presented, showing the influence of purity degree, Mn- and C-content in combination with the steelmaking practice. The influence of residual stress on the SSCC resistance of SAW pipe was pointed out and a heat treatment process was presented reducing the residual stress and resulting in crack free spiral welded pipes under the most severe test condition of NACE-solution with pH-values of 2.7–3.5. 相似文献
99.
100.
Andrea Burdzik Markus Stähler Irene Friedrich Marcelo Carmo Detlef Stolten 《Journal of Coatings Technology and Research》2018,15(6):1423-1432
Electrodes for polymer electrolyte membrane electrolyzers and fuel cells are manufactured by coating a catalyst dispersion, consisting of precious metal, ionomer and solvents, onto a substrate that is subsequently dried. One target of current research is to produce square meter-sized electrodes, but so far the homogeneity that can be achieved in this scaling is unclear. To quantify the achievable homogeneity of an electrode, manufactured by means of slot die coating in a roll-to-roll pilot plant, this study focuses first on the selection of an appropriate substrate by investigating thickness, basis weight and surface free energy distribution at the square meter scale. Afterward, a dispersion is coated on the selected substrate, dried and investigated with respect to thickness and basis weight distribution. Among the investigated substrates, Kapton has the smallest scatter in terms of thickness and basis weight. The subsequent coating results in a precious metal loading of 1.10 mg cm\(^{-2}\), with a scattering of 5.5% that can be further reduced to 4.5% when edge effects can be prevented. These results are now available for further research in which it is necessary to investigate whether or not these fluctuations affect the achievable electrochemical efficiencies of electrodes. 相似文献