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121.
122.
Motoko Wakabayashi Hidehiko Wakabayashi Wolfgang Eisenreich Yasujiro Morimitsu Kikue Kubota Karl-Heinz Engel 《European Food Research and Technology》2011,232(5):753-760
To determine the capillary gas chromatographic (GC) elution order of the enantiomers of 4-mercapto-2-alkanones, racemic 4-acetylthio-2-alkanones
were synthesized and hydrolyzed by lipases to get enantio-enriched 4-mercapto-2-alkanones that were resolved by capillary
gas chromatography using a chiral stationary phase. The obtained enantio-enriched 4-mercapto-2-alkanones were esterified with
(S)-2-methoxy-2-(1-naphthyl)propionic acid ((S)-MαNP acid), and the HPLC analysis of MαNP thioesters revealed the same isomeric ratios as the chiral GC analysis of the
corresponding thiol enantiomers. The diastereoisomeric thioesters obtained were resolved by HPLC, and the absolute configurations
were determined on the basis of 1H NMR anisotropy effects. On the basis of these results, the GC elution order of the enantiomers of 4-mercapto-2-alkanones
and of the corresponding 4-acetylthio-2-alkanones could be determined. The combination of enzymatic resolution and MαNP thioesterification
proved to be a useful tool to determine the absolute configuration of secondary thiols. 相似文献
123.
124.
Aspects of high hydrostatic pressure food processing: Perspectives on technology and food safety 总被引:1,自引:0,他引:1
Kemal Aganovic Christian Hertel Rudi. F. Vogel Reimar Johne Oliver Schlüter Uwe Schwarzenbolz Henry Jäger Thomas Holzhauser Johannes Bergmair Angelika Roth Robert Sevenich Niels Bandick Sabine E. Kulling Dietrich Knorr Karl-Heinz Engel Volker Heinz 《Comprehensive Reviews in Food Science and Food Safety》2021,20(4):3225-3266
The last two decades saw a steady increase of high hydrostatic pressure (HHP) used for treatment of foods. Although the science of biomaterials exposed to high pressure started more than a century ago, there still seem to be a number of unanswered questions regarding safety of foods processed using HHP. This review gives an overview on historical development and fundamental aspects of HHP, as well as on potential risks associated with HHP food applications based on available literature. Beside the combination of pressure and temperature, as major factors impacting inactivation of vegetative bacterial cells, bacterial endospores, viruses, and parasites, factors, such as food matrix, water content, presence of dissolved substances, and pH value, also have significant influence on their inactivation by pressure. As a result, pressure treatment of foods should be considered for specific food groups and in accordance with their specific chemical and physical properties. The pressure necessary for inactivation of viruses is in many instances slightly lower than that for vegetative bacterial cells; however, data for food relevant human virus types are missing due to the lack of methods for determining their infectivity. Parasites can be inactivated by comparatively lower pressure than vegetative bacterial cells. The degrees to which chemical reactions progress under pressure treatments are different to those of conventional thermal processes, for example, HHP leads to lower amounts of acrylamide and furan. Additionally, the formation of new unknown or unexpected substances has not yet been observed. To date, no safety-relevant chemical changes have been described for foods treated by HHP. Based on existing sensitization to non-HHP-treated food, the allergenic potential of HHP-treated food is more likely to be equivalent to untreated food. Initial findings on changes in packaging materials under HHP have not yet been adequately supported by scientific data. 相似文献
125.
A Gazzinelli MF Gazzinelli MM Cadete S Pena Filho IR Sá H Kloos 《Canadian Metallurgical Quarterly》1998,14(4):841-849
A study to determine the sociocultural factors influencing knowledge, attitudes, and practices of individuals from a small community toward Schistosoma mansoni infection was carried out in an endemic area in the State of Minas Gerais, Brazil. The study used qualitative approaches to collect data from school-aged children and teachers. Specific findings were that the individuals interviewed were aware of the disease, but also held inaccurate popular beliefs about transmission. Misconceptions coexisted with accurate knowledge both in children and teachers. The disease was not seen as a major health problem and does not affect their activities since it does not cause severe symptoms in most of the individuals. Although the majority of the participants relate transmission to water and lack of sanitation, they do not take any preventive measures since their subsistence is highly dependent on irrigation, farming, fishing, and other essential work that is directly related to water activities. The authors discuss the development of a health education program based on the knowledge and perception of individuals about the disease and its determinants as being important for the context and behavioral change. 相似文献
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127.
Creep and Creep Rupture Behaviour of Heat Resistant Steels under Variable Loading Conditions The creep and creep rupture behaviour under rectangular cyclical conditions was measured on 8 typical heat resistant steels up to 35 000 h test duration. The results are described by the modified life fraction rule. The main dependencies of the characteristic of that rule, the relative life, are investigated. Concepts for the evaluation of the relative life are presented in regard to design and supervision of components. 相似文献
128.
129.
Choice and operation of vapour compressors in chemical production plant . The use of vapour compressors for evaporation, distillation processes and also for more complex processes has increased greatly due to the large increases in energy costs in the past. Generally, high speed radial compressors are used for these applications. Recommended operating ranges, investment costs as well as efficiencies at different compression ratios are explained, based on experience gained in technical application and manufacturers information. The example of combining a separation column and an evaporation step shows that not only a saving of energy, but also a significant reduction of waste water generation is achieved. The control strategy for a process having several recycle flow streams is explained. Based on operating experience, recommendations for field monitoring of the compressor are given. 相似文献
130.
Effect of Surface Cold Working on Fatigue Strength and Cyclic Stress-Strain Behaviour of Normalized Plain Carbon Steels Ck 15 and Ck 45 under Compression-Tension and Rotating Bending Load Investigations on deep rolled specimens of normalized plain carbon steels showed that surface could working can improve the fatigue strength by about 15% in rotating bending tests and by about 5% in cyclic compression-tension tests. The better endurance properties are mainly caused by a reduced amplitude of plastic strain. From microscopical examinations of Ck 15 surfaces was deduced that crack initiation in deep rolled specimens resembles by far with that in specimens not surface treated. During fatigue tests the dislocation structure produced by deep rolling approached that developing in samples without cold worked surface. 相似文献