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71.
W. Postel F. Drawert und W. Hagen 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1973,150(5):267-273
Zusammenfassung In 99 Weinen wurde der Gehalt anl(+)- undd(–)-Lactat enzymatisch bestimmt. Die in der Literatur vorgeschlagene alkalische Verseifung des Weins darf nicht durchgeführt werden, da dies zu stark fehlerhaften Ergebnissen durch die Bildung von Milchsäure aus dem Restzucker der Weine führt. Auf einen Aufschluß durch Säure oder durch Kochen kann verzichtet werden, da die gebundene Menge an Milchsäure im Wein nur zu maximal 100–200 mg/l festgestellt wurde. Wenn nur der Gesamtlactatgehalt interessiert, so kann dieser ebenfalls enzymatisch ohne Differenzierung in die stereoisomeren Formen direkt bestimmt werden. Die Fehlerbreite der Methode ist gering; es besteht eine gute Übereinstimmung mit der chemischen Methode von Rebelein.Bei den untersuchten Weinen variiert bei einem Gesamt-Milchsäuregehalt von 0,10–5,61 g/l der Gehalt an L-Lactat zwischen 0,00 und 4,82 g/l, der Gehalt an D-Lactat zwischen 0,05 und 0,84 g/l. Bei niedrigen Gesamt-Milchsäuregehalten von weniger als 0,6 g/1 kann sowohld-Lactat als auchl-Lactat überwiegen. Je höher die Gesamt-Milchsäuregehalte ansteigen, desto mehr überwiegt dasl-Lactat, dessen Anteil bei Gesamt-Milchsäuregehalten von über 2 g/1 mehr als 80 bzw. 90% des Gesamtlactats beträgt.
Herrn G. Maccagnan danken wir für die Durchführung zahlreicher Analysen. 相似文献
Enzymatic investigations on the contents ofl(+)- andd(–)-lactic acid in wines
Summary Contents ofl(+)- andd(–)-lactic acid in 99 wines have been determined enzymatically. Alkaline hydrolysis of the wines, as proposed in the literature, should not be carried out, because erronious results are hereby obtained, due to the formation of lactic acid from the residual sugars of the wines.Acidic hydrolysis or heating may be dropped because the amounts of esterified lactic acid in wines have been ascertained to be only 100–200 mg/l (max.). If just interested in total lactic acid, disregarding any differentiation of stereoisomeres, then total lactic acid can also be directly determined enzymatically. The method only has a slight marginal error and the results are in good agreement with the chemical method by Rebelein.The content of total lactic acid varies from 0,10–5,61 g/1; ofl-lactic acid from 0,00–4,82 g/l and ofd-lactic acid from 0,05–0,84 g/l. In wines with very low content of total lactic acid (< 0,6 g/l),d-lactic acid as well as L-lactic acid may be the dominent isomere. However, the higher the content of total lactic acid the more pronounced the content Ofl-lactic acid is. In wines containing more than 2 g/l of total lactic acid, more than 80-90% are taken up byl-lactic acid.
Herrn G. Maccagnan danken wir für die Durchführung zahlreicher Analysen. 相似文献
72.
73.
Sex differences in driving performance. 总被引:1,自引:0,他引:1
R E Hagen 《Human factors》1975,17(2):165-171
74.
Ethane was converted into aromatic hydrocarbons on H-ZSM-5 and Zn-ZSM-5 at 773 K in a flow reactor system using nitrogen and hydrogen as carrier gases. Residence time was varied by changing catalyst weights to obtain information about primary and secondary reaction steps. On H-ZSM-5 ethane conversion proceeds via formation of ethene and subsequent oligomerization. Oligomers undergo fast isomerization, cracking and cyclization leading to a broad spectrum of aromatics. Methane is a secondary product. Dehydrogenation reactions proceed irreversibly. Introduction of zinc species significantly enhances the aromatization activity of H-ZSM-5 on the one hand and causes a change of reaction mechanism on the other. Oligomerization of olefinic intermediates can take place at zinc sites. In nitrogen, aromatization of C6 olefins is faster than isomerization and cracking of these oligomers. Dehydrogenation steps proceed reversibly. On using hydrogen as the carrier gas over Zn-ZSM-5, the conversion of ethane as well as the formation of aromatics decrease. Furthermore, aromatics richer in hydrogen (especially C8 aromatics) are then formed preferentially. 相似文献
75.
76.
The detection and measurement of antibodies in bloodstains represents a departure from the classical blood grouping used routinely in forensic serology. The antibodies in question are those associated with atopic allergy and infections by micro-organisms and other parasites. The production of these antibodies is not primarily under genetic control but reflects an individual's reaction to his environment. This paper describes the explicit information which may be obtained from an antibody profile, the high discriminating power and other advantages of the method. 相似文献
77.
About 20% of all women with insulin-dependent diabetes mellitus (IDDM) have menstrual irregularities. Eight percent have amenorrhea. Fluctuations in blood glucose and insulin concentration are probably contributing factors, but the irregular menstrual cycles are mainly caused by disorders in the central ovulatory mechanisms. Hypothalamic GnRH release is regulated by several neuropeptides. Dopamine and opiates exert an inhibitory effect, and there is evidence for an abnormally high dopaminergic hypothalamic activity among women with IDDM. There might also be disorders of the opioid, serotonergic and GABA'ergic systems, but the consequences of there possibilities remain uncertain. 相似文献
78.
79.
Wolters Christopher A.; Yu Shirley L.; Hagen John W.; Kail Robert 《Canadian Metallurgical Quarterly》1996,64(6):1397
The present study was designed to examine recall and rehearsal in short-term memory among children with insulin-dependent diabetes mellitus (IDDM). Children with onset of IDDM before age 5 years, children with onset after 5 years, and children without IDDM were administered a measure of short-term memory that provides information about rehearsal as well as level of recall. Children with later onset of diabetes and children without IDDM were expected to recall more words and use more effective rehearsal strategies than children with early onset of diabetes. Results indicate that children diagnosed with IDDM early in life used similar rehearsal strategies but recalled fewer words than children with later onset of diabetes and children without IDDM. In addition, results provide evidence that children who are in poor control of their diabetes did not use strategies designed to increase recall as often, or as well as, children in better control of their diabetes. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
80.