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111.
Dorothea Ehlers Michael Pfister Stefan Bartholomae 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1994,199(1):38-42
In the literature there is contradictory information on the compounds of Tahiti vanilla, particularly concerning the piperonal content. Because of this, Tahitian beans and Tahiti vanilla resinoid were analysed by HPLC. Compared with results obtained onVanilla planifolia, the Tahitian beans contained relatively low amounts of vanillin and vanillic acid, relatively high amounts ofp-hydroxybenzoic acid and considerable amounts of anisic acid and anisyl alcohol. Furthermore, although anisaldehyde was detectable, 3-ethoxy-4-hydroxy-benzaldehyde (ethylvanillin), coumarin and piperonal were not. The resinoid contained the same compounds as the beans in the expected amounts and ratios. It has to be supposed that reports of positive piperonal results refer to research on adulterated vanilla beans.
Hochdruckflüssigchromatographische Untersuchung von Tahiti-Vanille
Zusammenfassung In der Literatur finden sich widersprüchliche Angaben über die Zusammensetzung von Tahiti-Vanille, insbesondere im Hinblick auf einen Piperonalgehalt. Mittels HPLC wurden Untersuchungen an Tahiti-Vanille-Schoten und Tahiti-Vanille-Resinoid durchgeführt. Im Vergleich mitVanilla planifolia enthielten die Schoten relativ niedrige Gehalte an Vanillin und Vanillinsäure, relativ hohe Gehalte anp-Hydroxybenzoesäure sowie erhebliche Mengen an Anissäure und Anisalkohol. Weiterhin war Anisaldehyd, nicht jedoch 3-Ethoxy-4-hydroxy-benzaldehyd (Ethylvanillin49d), Cumarin oder Piperonal nachweisbar. Im Resinoid lagen die gleichen Inhaltsstoffe vor wie in den Schoten und entsprachen hinsichtlich Menge und Mengenverhältnis den erwarteten Werten. Es wird vermutet, daß die positiven Piperonalbefunde aus der Literatur auf einer Untersuchung verfälschter Vanilleschoten basieren.相似文献
112.
Dalia Hamdan Mahmoud Zaki El-Readi Ahmad Tahrani Florian Herrmann Dorothea Kaufmann Nawal Farrag Assem El-Shazly Michael Wink 《Food chemistry》2011
The fresh peel of Citrus jambhiri was extracted with aqueous methanol and the residue was fractionated using light petroleum, chloroform and ethyl acetate. The constituents of the extracts were separated by column chromatography employing solvents of different polarity. The chemical structure of the isolated compounds was then identified by MS and NMR. Column chromatography of the petroleum fraction resulted in the isolation of nobiletin, 5-O-demethylnobiletin, tangeretin, 5-hydroxy-3,6,7,8,3′,4′-hexamethoxyflavone, 3,5,6,7,8,3′,4′-heptamethoxyflavone, and a mixture of β-sitosterol and stigmasterol. The chloroform fraction afforded 6-demethoxynobiletin, 5,4′-dihydroxy-6,7,8,3′-tetramethoxyflavone, limonin and nomilin. The flavonoid glycosides naringin, hesperidin and neohesperidin were isolated from the ethyl acetate fraction. The chemical structure of the isolated compounds was established by MS and NMR (APT, COSY, HSQC, HMBC, and NOESY). LC–ESI-MS analysis of the ethyl acetate fraction afforded eight flavonoid glycosides, while the dichloromethane fraction of the defatted seeds contained seven limonoid aglycones. The chloroform fraction exerted the strongest DPPH∗ free radical scavenging activity in comparison to other fractions. The petroleum fraction showed a significant inhibition of lipoxygenase indicating an anti-inflammatory action (IC50 29 ± 1 μg/mL). Some of the isolated polymethoxyflavones exhibited strong cytotoxicity against COS7, HeLa and Caco-2 cell lines. 相似文献
113.
Dorothea M. Beutling Janina Peçonek Helga Stan-Lotter 《European Food Research and Technology》2009,229(5):725-730
The species Chromohalobacter beijerinckii comb. nov. was recently proposed in order to accommodate strain Pseudomonas beijerinckii Hof 1935, which was found in salted beans, and a novel isolate, strain 3b, which was obtained from salted herrings of the Baltic sea. The species is psychrophilic, growing from 5 to 42 °C and highly salt-tolerant, growing between 0.5 and 25% NaCl. Of interest to food microbiology are several properties, which are described here, such as the enzymatic activity of Ch. beijerinckii strain 3b against fish protein, cod liver oil and butter. In addition, the strain possesses decarboxylases of lysine, tyrosine and histidine and can thus be a producer of biogenic amines, mainly histamine and tyramine. In media containing 10% NaCl, Ch. beijerinckii strain 3b is resistant to the antibiotics bacitracin, chloramphenicol, streptomycin, tetracycline and novobiocin. The potential impact of these properties, especially of the biogenic amine content in salted food, which were not known so far from other species of the genus Chromohalobacter, is discussed. 相似文献
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Nine Holstein heifers whose estrous cycles were synchronized were observed during three subsequent consecutive cycles. Observations of heifers during each periestrus period began when the first heifer reached day 15 of an estrous cycle and ended 36 h after onset of estrus for the ninth heifer. There were 118 1-h observations at 6-h intervals during the three periestrus periods. Estrous cycles were divided into postestrual, luteal, preestrual, and estrual stages by blood progesterone profiles and estrus. Heifers of these four stages accounted for 27.5, 48.3, 15.4, and 8.8% of heifers available to mount during the 118 observations, and heifers of each stage made 9.0, 5.2, 18.9, and 66.9% of attempted mounts. When number of heifers in estrus simultaneously increased from one to five, total attempted mounts and stands per hour increased from 10.1 to 63.5 and from 4.5 to 48.5. Stands per heifer per hour increased significantly as number of heifers in estrus increased from one to two and tended to increase as number in estrus increased further. Presence of one preestrual heifer in a group containing one estrual heifer increased total stands per hour from 2.3 to 5.0. Efficiency of detection of estrus may depend on proportion of animals within estrous cycle stages that have highest mounting activity. 相似文献
116.
Sören Preibusch Dorothea Kübler Alastair R. Beresford 《Electronic Commerce Research》2013,13(4):423-455
In previous privacy studies, consumers have reported their unease with online retailers that collect a lot of personal data. Consumers claim they will switch to alternative providers or cancel transactions if data collection is deemed excessive. Therefore, privacy appears to be a competitive factor in electronic commerce. This paper describes a study which quantifies the degree to which privacy is a competitive advantage for online retailers. In an experiment, we offered 225 participants the option to purchase one DVD from one of two online stores. Throughout the study, one online shop asked for more invasive personal data—as confirmed by an exit-questionnaire. In the test treatment, the privacy-invasive store sold DVDs for one Euro less than the other, and in the control treatment, both stores sold DVDs for the same price. Across both treatments, 74 participants made a purchase and had the DVD they bought delivered. In our study we found that, when the price of DVDs was the same between both stores, the shop asking for less personal data did not amass the entire market. When consumers were offered a trade-off between price and privacy, the vast majority of customers chose to buy from the cheaper, more privacy-invasive, firm; this firm got both a larger market share and higher revenue. The cheaper shop generated strong dissatisfaction with their privacy practises; in contrast, consumers of the more expensive store displayed only weak dissatisfaction with price. We established the validity of our analysis by checking users made informed choices, and did not select one firm over the other due to hasty decision-making or ordering effects. We found no support for either a materialistic lifestyle nor the quest for immediate gratification as to why customers chose the cheaper but privacy-unfriendly store. 相似文献
117.
Helmer Strik Micha Hulsbosch Catia Cucchiarini 《Language Resources and Evaluation》2010,44(1-2):41-58
The present paper investigates multiword expressions (MWEs) in spoken language and possible ways of identifying MWEs automatically in speech corpora. Two MWEs that emerged from previous studies and that occur frequently in Dutch are analyzed to study their pronunciation characteristics and compare them to those of other utterances in a large speech corpus. The analyses reveal that these MWEs display extreme pronunciation variation and reduction, i.e., many phonemes and even syllables are deleted. Several measures of pronunciation reduction are calculated for these two MWEs and for all other utterances in the corpus. Five of these measures are more than twice as high for the MWEs, thus indicating considerable reduction. One overall measure of pronunciation deviation is then calculated and used to automatically identify MWEs in a large speech corpus. The results show that neither this overall measure, nor frequency of co-occurrence alone are suitable for identifying MWEs. The best results are obtained by using a metric that combines overall pronunciation reduction with weighted frequency. In this way, recurring “islands of pronunciation reduction” that contain (potential) MWEs can be identified in a large speech corpus. 相似文献
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120.
Norbert Helle Anne Wolbert Bettina Linke Dorothea Ehlers Karl -Ernst Krüger 《European Food Research and Technology》1995,201(4):355-360
This paper describes the development of a method for the identification of irradiated fresh fruits by measurement of the e.p.r. spectra of pips, kernels or stones. Measurement parameters were optimized and the irradiation specific spectrum was assigned to a cellulose radical by comparison with the e.p.r. spectrum of pure cellulose. Several fruits especially different varieties of strawberries were examined giving the following results: Detectable minimum doses were between 0.4 kGy and 0.9 kGy and the intensity of the irradiation specific signals was found to be linear up to doses of 11 kGy. The lifetime of the specific radicals (at room temperature and at deep freezing temperatures) was long enough compared to the storage time of fresh fruits. Additional information about the nature of the unspecific central signal was gained measuring the samples which were stored at different temperatures. The main conclusion of this study is that the e.p.r. method seemes to be well suited for the use in routine control and should be tested in an intercomparison to establish a routine method for the identification of irradiated fresh fruits. 相似文献