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Analyse der reifungsbedingten Veränderungen und Einflussfaktoren auf das Metabolom von Rindfleisch
Full text linkAging of beef is necessary to improve its flavor and tenderness. There are two most common aging types, dry-aging and wet-aging. Dry-aged beef is often associated with a higher eating quality than wet-aged beef. The term “dry-aged beef” is not legally defined, so authentication methods are needed to protect the consumers from food fraud.
During beef aging, the metabolome of beef changes due to the postmortem metabolism. This dissertation focuses on the aging method as a postmortem process and the resulting changes in the metabolome. As a hypothesis of this study, it was postulated that the detection of these metabolic changes due to aging of beef is feasible by 1H NMR spectroscopy and based on these measurements the evaluation of an authentication model for the aging method of beef is possible. In order to test this hypothesis, a sample preparation and measurement method was developed and based on this, potential influencing factors such as sampling position in muscle, breed and sex were investigated on the metabolome of fresh and aged beef.
In the first part of this thesis, the sample preparation and the 1H NMR measurement method were developed. In the sample preparation, the polar fraction of the metabolome was extracted from 200 mg of beef, allowing 24 samples to be prepared in parallel. The sample preparation and the measurement method were validated, and the first aged beef samples were analyzed to check if the aging-related changes in the metabolome could be detected by this method.
In the second part of this thesis, the sampling position in the muscle were analyzed for changes or differences in the metabolome due to its location in the muscle. The results showed that the metabolome changes along the length of the M. longissimus thoracis et lumborum, but the influence of the aging type and aging time was more pronounced in the metabolome of beef. The comparison of the surface and the inner part of wet-aged and dry-aged beef showed that the metabolome of dry-aged beef differed greatly between the surface and the inner part, despite the exclusion of the moisture content by freeze-drying and the low microbial load. There were only slight differences between the surface and the inner part for wet-aged beef, which could be due to the influence of microbiota and their metabolites. Therefore, the sampling location in the M. longissimus thoracis et lumborum was determined as precisely as possible for the further studies. The muscles were cut into ten pieces from cranial to caudal and dry-aged or wet-aged for 0, 7, 14, 21, and 28 days, in duplicates.
The third part of this thesis focuses on the potential influencing factors such as breed and sex of the animals. Fresh and aged beef samples from three cattle types (heifer, cow, and young bull) and two different breeds (‘Fleckvieh’ and ‘Schwarzbunt’) were analyzed by targeted and non-targeted 1H NMR spectroscopy. Both factors were shown to influence the metabolome of fresh and aged beef. Therefore, these factors had to be included in the authentication model based on both targeted and non-targeted model. The calculation of the authentication model was the main part of this thesis and showed a good prediction of cattle type, breed, aging time and aging type of beef. The authentication model was based on the combination of multiple models of PLS-R and PLS-DA. The model for predicting the cattle type showed an accuracy of 99 %, and the models for predicting the breed depending on the cattle type showed an accuracy of 100 %. Aging time could be predicted with an error of 2.28 days. The statistical models for aging type were separated by aging time based on the determination of aging time. The model for predicting the aging type of 28-day aged samples had an accuracy of 99 %. The other statistical models for predicting aging type were additionally separated by cattle type and breed, and their accuracy ranged from 90 % to 100 %.
In conclusion, an authentication model to determine the cattle type, breed, aging time and aging type of beef was developed in this dissertation. Therefore, it is possible to authenticate beef samples using a single 1H NMR spectrum. In future studies, it would be useful to extend this authentication model to other samples of other breeds and influencing factors.Mit der Reifung von Rindfleisch kann der Geschmack und die Zartheit des Fleisches verbessert werden. Es gibt zwei gängige Reifungstypen: Trockenreifung und Nassreifung. „Dry-aged“ Rindfleisch wird oft mit einer höheren Genussqualität in Verbindung gebracht als wet-aged Rindfleisch. Der Begriff "dry-aged beef" ist rechtlich nicht definiert, weshalb Authentifizierungsmethoden erforderlich sind, um die Verbraucher vor Lebensmitteltäuschung zu schützen.
Während der Reifung von Rindfleisch verändert sich das Metabolom von Rindfleisch aufgrund des postmortalen Stoffwechsels. Diese Dissertation konzentriert sich auf die Reifungsmethode als postmortale Behandlung des Fleisches und die daraus resultierenden Veränderungen im Metabolom. Als Hypothese dieser Studie wurde postuliert, dass der Nachweis dieser Stoffwechselveränderungen durch die Reifung von Rindfleisch mittels 1H-NMR-Spektroskopie möglich ist und auf Basis dieser Messungen die Evaluierung eines Authentifizierungsmodells für die Reifungsmethode von Rindfleisch möglich ist. Um diese Hypothese zu überprüfen, wurde eine Probenvorbereitungs- und Messmethode entwickelt, die die Basis für die Untersuchungen möglicher Einflussfaktoren wie die Probenahmeposition im Muskel, Rasse oder Geschlecht auf das Metabolom von frischem und gereiftem Rindfleisch untersucht.
Im ersten Teil dieser Arbeit wurden die Probenvorbereitung und die 1H-NMR-Messmethode entwickelt. Bei der Probenvorbereitung wurde die polare Fraktion des Metaboloms aus 200 mg Rindfleisch extrahiert, was die parallele Vorbereitung von 24 Proben ermöglichte. Die Probenvorbereitung und die Messmethode wurden validiert, und die ersten gereiften Rindfleischproben analysiert, um zu prüfen, ob die reifungsbedingten Veränderungen im Metabolom mit dieser Methode nachweisbar waren.
Im zweiten Teil dieser Arbeit wurde die Lage der Probenahmeposition im Muskel auf Veränderungen oder Unterschiede im Metabolom analysiert. Die Ergebnisse zeigten, dass sich das Metabolom über die Länge des M. longissimus thoracis et lumborum verändert, aber der Einfluss der Reifeart und der Reifezeit auf das Metabolom von Rindfleisch stärker ausgeprägt war. Der Vergleich der Oberfläche und des inneren Teils von wet-aged und dry-aged Rindfleisch zeigte, dass sich das Metabolom von dry-aged Rindfleisch trotz des einheitlichen Bezugs auf die Trockenmasse durch Gefriertrocknung und trotz sehr geringer mikrobieller Belastung stark zwischen Oberfläche und innerem Teil unterscheidet. Bei wet-aged Rindfleisch gab es nur geringe Unterschiede zwischen der Oberfläche und dem inneren Teil, was auf den Einfluss der Mikrobiota und ihrer Stoffwechselprodukte zurückzuführen sein könnte. Daher wurde die Probenahmeposition im M. longissimus thoracis et lumborum für die weiteren Untersuchungen definiert. Die Muskeln wurden von kranial nach kaudal in zehn Stücke geschnitten und in Duplikaten 0, 7, 14, 21 und 28 Tage lang trocken (dry) oder nass (wet) gereift.
Der dritte Teil dieser Arbeit befasste sich mit möglichen Einflussfaktoren wie Rasse und Geschlecht der Tiere. Frische und gereifte Rindfleischproben der drei Rindertypen (Färse, Kuh und Jungbulle) und der zwei verschiedenen Rassen ("Fleckvieh" und "Schwarzbunt") wurden mittels targeted (zielgerichteter) und non-targeted (nicht-zielgerichter) 1H-NMR-Spektroskopie analysiert. Es zeigte sich, dass beide Faktoren (Rindertyp und Rasse) das Metabolom von frischem und gereiftem Rindfleisch beeinflussen. Daher mussten sie in das Authentifizierungsmodell, basierend auf dem targeted oder non-targeted Ansatz, einbezogen werden. Die Berechnung des Authentifizierungsmodells war ein Hauptteil dieser Arbeit. Der non-targeted Ansatz zeigte eine gute Vorhersage des Rindertyps, der Rasse, der Reifezeit und der Reifeart von Rindfleisch. Das Authentifizierungsmodell basierte auf der Kombination mehrerer statistischer Modelle von PLS-R und PLS-DA. Das Modell zur Vorhersage des Rindertyps zeigte eine Genauigkeit von 99 %, und die Modelle zur Vorhersage der Rasse in Abhängigkeit vom Rindertyp zeigten eine Genauigkeit von 100 %. Die Reifezeit konnte mit einem Fehler von 2,28 Tagen vorhergesagt werden. Auf der Grundlage der Bestimmung der Reifezeit wurden die statistischen Modelle für die Reifeart nach Reifezeit getrennt. Das Modell zur Vorhersage der Reifeart von 28 Tage gereiften Proben hatte eine Genauigkeit von 99,6 %. Die weiteren statistischen Modelle zur Vorhersage der Reifeart wurden zusätzlich nach Rindertyp und Rasse getrennt, und ihre Genauigkeit lag zwischen 90 und 100 %.
Zusammenfassend wurde in dieser Dissertation ein Authentifizierungsmodell für die Bestimmung von Rindertyp, Rasse, Reifezeit und Reifeart von Rindfleisch entwickelt. Daher ist es möglich, Rindfleischproben anhand eines einzigen 1H-NMR-Spektrums zu authentifizieren. In zukünftigen Studien wäre es sinnvoll, dieses Authentifizierungsmodell mit weiteren Proben anderer Rassen und Einflussfaktoren zu erweitern
A research note: effect of pH on meat iridescence in precooked cured pork
No full textObjective: The objective of this study was to investigate the effect of pH change of cooked cured pork M. longissimus thoracis et lumborum on iridescence intensity and extent (= percentage of iridescent area) since interaction with light may be related to pH-induced alterations in microstructure. Muscles were injected with brines of different pH values, cooked, sliced perpendicular to muscle fiber direction, and visually evaluated by a panel of 20 experienced panelists.
Results: Muscles with lowest pH (5.38) showed the lowest iridescence score of 4.63 (p 0.05). Iridescence was positively correlated (p < 0.01) with pH and water content, and negatively correlated (p < 0.01) with cooking loss. Hence, hydration state and light scattering from microstructure may be important factors that determine the degree of iridescence in cooked meat products.Open Access funding enabled and organized by Projekt DEAL.Forschungskreis der Ernährungsindustrie http://dx.doi.org/10.13039/501100008465Universität Hohenheim (3153
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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