Markus Fischer

University of Hamburg | UHH · Department of Chemistry, HAMBURG SCHOOL OF FOOD SCIENCE

The price of different truffle types varies according to their culinary value, sometimes by more than a factor of 10. Nonprofessionals can hardly distinguish visually the species within the white or black truffles, making the possibility of food fraud very easy. Therefore, the identification of different truffle species (Tuber spp.) is an analytica...

The untargeted metabolomics analysis of biological samples with nuclear magnetic resonance (NMR) provides highly complex data containing various signals from different molecules. To use these data for classification, e.g., in the context of food authentication, machine learning methods are used. These methods are usually applied as a black box, whi...

Accelerated storage is routinely used with pharmaceuticals to predict stability and degradation patterns over time. The aim of this is to assess the shelf life and quality under harsher conditions, providing crucial insights into their long-term stability and potential storage issues. This study explores the potential of transferring this approach...

Discovery of novel antibiotics needs multidiscliplinary approaches to gain target enzyme and bacterial activity while aiming for selectivity over mammalian cells. Here we report a multi‐parameter optimisation of a fragment‐like hit that was identified through a structure‐based virtual screening campaign on Escherichia coli IspE crystal structure. S...

Deazaflavins are important analogues of the naturally occurring flavins: riboflavin, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). The use of 5-deazaflavin as replacement coenzyme in a number of flavoproteins has proven particularly valuable in unraveling and manipulating their reaction mechanisms. It was frequently reported th...

Deazaflavins are important analogues of the naturally occurring flavins: riboflavin, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). The use of 5‐deazaflavin as replacement coenzyme in a number of flavoproteins has proven particularly valuable in unraveling and manipulating their reaction mechanisms. It was frequently reported th...

Nutmeg is a popular spice often used in ground form, which makes it highly susceptible to food fraud. Therefore, the aim of the present study was to detect adulteration of ground nutmeg with nutmeg shell via Fourier transform near-infrared (FT-NIR) spectroscopy. For this purpose, 36 authentic nutmeg samples and 10 nutmeg shell samples were analyzed...

The importance of animal welfare and the organic production of chicken eggs has increased in the European Union in recent years. Legal regulation for organic husbandry makes the production of organic chicken eggs more expensive compared to conventional husbandry and thus increases the risk of food fraud. Therefore, the aim of this study was to deve...

This review explains the strategies behind genomics, proteomics, metabolomics, metallomics and isotopolomics approaches and their applicability to written artefacts. The respective sub-chapters give an insight into the analytical procedure and the conclusions drawn from such analyses. A distinction is made between information that can be obtained f...

Unlabelled: To prevent food fraud, products can be monitored by various chemical-analytical techniques. In this study, we present a CRISPR-Cpf1 DETECTR-based assay for the differentiation of plant ingredients in sweet confectionary like fine and bulk-cocoa, or bitter and sweet almonds. To enable rapid in-field analysis, the trans-cleavage activity...

Oregano (Origanum vulgare and O. onites) is one of the most frequently counterfeited herbs in the world and is diluted with the leaves of a wide variety of plants. In addition to olive leaves, marjoram (O. majorana) is often used for this purpose in order to achieve a higher profit. However, apart from arbutin, no marker metabolites are known to re...

Lipids make up more than half of the human brain's dry weight, yet the composition and function of the brain lipidome is not well characterized. They not only provide the structural basis of cell membranes, but also take part in a wide variety of biochemical processes. In neurodegenerative diseases, lipids can facilitate neuroprotection and serve a...

Aptamers offer several advantages over antibodies. However, to ensure high affinity and specificity, a better understanding of the interactions between the nucleic-acid-based aptamers and their targets is mandatory. Therefore, we investigated the influence of two physical properties of proteins—molecular mass and charge—on the affinity of nucleic-a...

Top-down proteomics deals with the characterization of intact biomolecules, which reduces the sample complexity and facilitates the detection of modifications at the protein level. The combination of the matrix-assisted laser desorption/ionization (MALDI) technique with time-of-flight (TOF) mass analysis allows for the generation of gaseous ions in...

The determination of the cocoa shell content is of interest because a high shell content causes a reduction in the quality of cocoa products. Consequently, the aim of the present study was the development of a routinely applicable method for the quantitation of shell material in cocoa nibs. For this, 51 fermented cocoa samples of different varietie...

Storage is a critical step in the post-harvest processing of hazelnuts, as it can lead to mold, rancidity, and off-flavor. However, there is a lack of analytical methods to detect improper or extended storage. To comprehensively investigate the effects of hazelnut storage, samples were stored under five different conditions for up to 18 months. Sub...

To address the continued rise of multi-drug-resistant microorganisms, the development of novel drugs with new modes of action is urgently required. While humans biosynthesize the essential isoprenoid precursors isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) via the established mevalonate pathway, pathogenic protozoa and certain...

The analytical requirements for food testing have increased significantly in recent years. On the one hand, because food fraud is becoming an ever‐greater challenge worldwide, and on the other hand because food safety is often difficult to monitor due to the far‐reaching trade chains. In addition, the expectations of consumers on the quality of foo...

In the present manuscript, we describe how we successfully used ligand-based virtual screening (LBVS) to identify two small-molecule, drug-like hit classes with excellent ADMET profiles against the difficult to address microbial enzyme 1-deoxy-d-xylulose-5-phosphate synthase (DXPS). In the fight against antimicrobial resistance (AMR), it has become...

Storage is a critical step in post-harvest processing of hazelnuts since it can lead to mold, rancidity and off-flavor. To comprehensively investigate the effects of hazelnut storage, samples were stored under three short-term and two long-term conditions and the polar metabolome was analyzed by 1H NMR spectroscopy at different time points. Large d...

Cocoa cultivation is dominated by the clone "Colleción Castro Naranjal 51" (CCN-51). In contrast, CCN-51 is the expensive and aromatic fine cocoa "Arriba Nacional" from Ecuador. The differences in the overall quality of the beans and in the prices show that it is necessary to develop a rapid and accurate method to distinguish these varieties and pr...

Near-infrared (NIR) spectroscopy is a proven tool for the determination of food authenticity, mainly because of good classification results and the possibility of industrial use due to its easy and fast application. Since water shows broad absorption bands, the water content of a sample should be as low as possible. Freeze-drying is a commonly used...

Truffles are appreciated as food all over the world because of their extraordinary aroma. However, quantities are limited and successful cultivation in plantations is very labor-intensive and expensive, or even impossible for some species. These factors make truffles a very valuable food, which is why it is particularly rewarding and tempting to de...

We investigate the electronic structure of flavin semiquinone radicals in terms of their 13C hyperfine coupling constants. Photochemically induced dynamic nuclear polarization (photo-CIDNP) spectroscopy was used to study both the neutral and anionic radical species of flavin mononucleotide (FMN) in bulk aqueous solution. Apart from universally 13C-...

Storage is a critical step in post-harvest processing of hazelnuts since it can lead to mold, rancidity and off-flavor. To comprehensively investigate the effects of hazelnut storage, samples were stored under three short-term and two long-term conditions and the polar metabolome was analyzed by 1H NMR spectroscopy at different timepoints. Large di...

Food fraud is a growing problem, especially misdeclaration due to regional price differences offering a wide field. Fast, powerful, and cost-effective analytical methods are therefore essential to counteract food fraud. The isotopolome is suitable for origin discrimination and was analyzed in this study using laser ablation inductively coupled plas...

In the present manuscript, we describe how we successfully used ligand-based virtual screening (LBVS) to identify two small-molecule, drug-like hit classes with excellent ADMET profiles against the difficult to address microbial enzyme 1-deoxy-D-xylulose-5-phosphate synthase (DXPS). In the fight against antimicrobial resistance (AMR) it has become...

In the present manuscript, we describe how we successfully used ligand-based virtual screening (LBVS) to identify two small-molecule, drug-like hit classes with excellent ADMET profiles against the difficult to address microbial enzyme 1-deoxy-D-xylulose-5-phosphate synthase (DXPS). In the fight against antimicrobial resistance (AMR) it has become...

In this study, the ability of Fourier-transform near-infrared (FT-NIR) spectroscopy to trace back the geographical origin of grain maize used as feed material was investigated. 101 milled grain maize samples from five different countries (Spain, Ukraine, Slovakia, Peru and the USA) and three continents were analysed by FT-NIR spectroscopy. The spec...

For the untargeted analysis of the metabolome of biological samples with liquid chromatography–mass spectrometry (LC-MS), high-dimensional data sets containing many different metabolites are obtained. Since the utilization of these complex data is challenging, different machine learning approaches have been developed. Those methods are usually appl...

The enzymes of the 2-C-methylerythritol-d-erythritol 4-phosphate (MEP) pathway (MEP pathway or non-mevalonate pathway) are responsible for the synthesis of universal precursors of the large and structurally diverse family of isoprenoids. This pathway is absent in humans, but present in many pathogenic organisms and plants, making it an attractive s...

Fourier-transform near-infrared (FT-NIR) spectroscopy was used to determine the geographical origin of 233 hazelnut samples of various varieties from five different countries (Germany, France, Georgia, Italy, Turkey). The experimental determination of the geographical origin of hazelnuts is important, because there are usually large price differenc...

A non-targeted metabolomics-based approach using liquid chromatography high-resolution mass spectrometry was used to authenticate spruce wood (Picea abies) from two geographic source areas. The two sample sites were located in Germany and only 250 km apart. In order to achieve the highest possible metabolite coverage, the spruces samples were measu...

In the last decade, research efforts to develop non-targeted metabolomics strategies, especially for the detection of various food authenticity parameters, have increased significantly. However, such methods are hardly implemented in routine analysis so far, which is due to the relatively expensive equipment as well as the lack of reference databas...

Food fraud is a pervasive issue; products with high sales and region-dependent prices are strongly affected. In this study, isotopolomic fingerprinting was used to distinguish the origin of almonds in order to prevent food fraud. For this purpose, 250 almond samples consisting of more than 30 varieties from six different countries and four crop yea...

Ancient manuscripts may contain a large amount of additional information besides the written words. This information is not readily visible to the naked eye and is also analytically very challenging to uncover. In the last ten years, mass spectrometric techniques in particular have emerged in this context to provide additional information about the...

Fourier-transform near-infrared (FT-NIR) spectroscopy was used to determine the geographical origin of 233 hazelnut samples of various varieties from five different countries (Germany, France, Georgia, Italy, Turkey). The experimental determination of the geographical origin of hazelnuts is important, because there are usually large price differenc...

Fourier-transform near-infrared (FT-NIR) spectroscopy was used to determine the geographical origin of 233 hazelnut samples of various varieties from five different countries (Germany, France, Georgia, Italy, Turkey). The experimental determination of the geographical origin of hazelnuts is important, because there are usually large price differenc...

Aufgrund verschiedener Kontaminationsrisiken und durch ständig verfeinerte Analysentechniken mit extrem niedrigen Erfassungsgrenzen sowie nicht zuletzt wegen eines geschärften Gesundheitsbewusstseins wird heute der Frage nach der Sicherheit der Lebensmittel vermehrte Bedeutung zugemessen wird. Beachtung findet dabei insbesondere die Problematik der...

Die Massenspektrometrie (MS) ist eine Methode zur Trennung und Messung von Ionen unterschiedlicher Masse in der Gasphase. Es wird das Masse-zu-Ladungsverhältnis (m/z) der Ionen gemessen und die Intensität des auf einen Detektor fallenden Ionenstrahls konzentrationsproportional aufgenommen. Der Ionisierungsgrad ist hierbei ein wichtiges Kriterium fü...

Methoden für die Analyse von Lebensmitteln können nach verschiedenen Erkenntnisformen differenziert werden. Unterschieden werden Methodenkategorien nach Merkmalsausprägung und Methodenarten nach Akzessibilität (Zugänglichkeit, Verfügbarkeit). Allen Methoden gemein ist, dass sie validiert sein müssen, um korrekte Ergebnisse erzielen zu können. Analy...

Die Gruppe der Kohlenhydrate umfasst niedermolekulare sowie mittelmolekulare bis hochmolekulare, polymere Verbindungen. Kohlenhydrate werden deshalb unterteilt in Mono-, Di-, Oligo- und Polysaccharide. Die den Kohlenhydraten handelt es sich um Polyhydroxycarbonylverbindungen sowie einige davon abgeleitete, strukturell ähnliche Stoffe. Mengenmäßig g...

Authentizität von Lebensmitteln bedeutet Originalität, Echtheit bzw. Unverfälschtheit. Alle im Rahmen der Omics-Analyse eingesetzten Verfahren folgen dem zunächst nicht-zielgerichteten Ansatz, das heißt, sie liefern elementare sowie molekulare Fingerabdrücke, die mit Referenzdatensätzen verglichen werden. Notwendig ist es hierbei, die Datenmenge, d...

Der Begriff der enzymatischen Analyse umfasst zwei prinzipiell unterschiedliche analytische Verfahrensweisen: Erstens, die analytische Bestimmung von Substanzen (Substraten) mit Hilfe von Enzymen, die sog. UV-Tests und zweitens, die Ermittlung von Enzymaktivitäten. Die enzymatische Substratbestimmung verbindet gleichzeitig alle Anforderungen, die a...

Bei der Untersuchung von Lebensmitteln stellen sich vor Beginn der Analyse stets die gleichen Fragen: Was soll wie, wann und warum untersucht werden und was bedeuten die Ergebnisse? Lebensmittel sind komplexe biologische Systeme, die auf unterschiedliche Art und Weise und auf unterschiedlichen Ebenen untersucht werden können. Um zielorientiert und...

Mit Hilfe der Polarographie lassen sich über das Strom-Spannungsverhalten einer polarisierbaren Elektrode während Oxidations- bzw. Reduktionsreaktionen Art und Quantität elektrochemisch aktiver Substanzen bestimmen. Bei der Polarographie wird eine tropfende Quecksilberelektrode, deren Oberfläche sich laufend erneuert, eingesetzt. Neben anorganische...

Neben der Auswahl der „richtigen“ Methode für die jeweilige analytische Fragestellung ist die richtige Interpretation der Ergebnisse ausschlaggebend für eine zuverlässige verlässliche Beurteilung von Lebensmitteln. Zu unterscheiden sind Parameter, die eine Beurteilung der Analysenmethode erlauben und Parameter, die Auskunft über Genauigkeit und Str...

Ein Qualitätsmanagementsystem bietet durch die Strukturierung seiner Aufbau- und Ablauforganisation dem Management die Möglichkeit zur wirksamen Steuerung und Kontrolle aller qualitätsrelevanten Tätigkeiten. Ziel muss dabei sein, mit einem Minimum an Kosten ein Maximum an Qualität zu realisieren. Dabei wird unter Qualität nicht etwa Exzellenz oder...

Lebensmittelzusatzstoffe sind Stoffe oder Stoffgemische, die bei der Herstellung von Lebensmitteln zur Erzielung chemischer, physikalischer (technologischer) oder auch physiologischer Effekte zum Einsatz kommen. Hierzu zählen auch Zuckeraustauschstoffe (mit Ausnahme der Fructose), die Vitamine A und D, Aminosäuren, Mineralstoffe und Spurenelemente....

Chromatographische Verfahren sind Trennverfahren, die darauf basieren, dass die zu trennenden Substanzen an zwei Phasen multiplikativ verteilt werden. Eine dieser Phasen ist immobil, das heißt, fixiert, die andere Phase ist beweglich. Beschrieben werden die Dünnschichtchromatographie (DC) an Normal- und Umkehr-Phasen, die Hochleistungs-Dünnschichtc...

Allen immunchemischen Verfahren ist gemeinsam, dass die Detektion des Analyten auf einer spezifischen Antigen-Antikörper-Reaktion beruht. Aufgrund der Spezifität der Antikörper gegenüber dem entsprechenden Antigen sind immunchemische Methoden geeignet, auch geringe Mengen an Antigen im Kontext einer komplexen Matrix nachzuweisen bzw. zu quantifizie...

Die eigentlichen Fette (Triglyceride) sind stickstofffreie organische Verbindungen, die im pflanzlichen und tierischen Stoffwechsel gebildet werden und physiologisch gesehen einen hohen Nährwert besitzen. Unter den Nährstoffen zählen sie zu den größten Energielieferanten. Fette sind in der Regel mit zahlreichen Begleitstoffen (Lipoiden) vergesellsc...

Kopplungstechniken beschreiben meist on-line-Verbindungen zweier oder mehrerer analytischer Verfahren. Prinzipiell gibt es vier verschiedene Kopplungsverfahren, als da wären: die Kopplung zweier unterschiedlicher Techniken; die Kopplung von Chromatographie und Spektrometrie, wie GC-MS, LC-MS/MS, ICP-MS, IRMS; die Kopplung zweier chromatographischer...

Aminosäuren sind fundamentale Bestandteile von Lebensmitteln und zudem notwendige Bausteine für die Proteinbiosynthese. Peptide entstehen durch Verknüpfung von Aminosäuren in einer definierten Reihenfolge über Säureamidbindungen. Peptide unterscheiden sich von Proteinen allein durch ihre Größe, d. h. Anzahl der verknüpften Aminosäuren. Proteine geh...

Die optischen, spektroskopischen bzw. spektrometrischen Verfahren in der analytischen Chemie beruhen auf einem gemeinsamen Merkmal, nämlich der Wechselwirkung von Materie und Energie in Form von Strahlung. Die Strahlung umfasst den Bereich der Radiowellen bis hin zu den Gammastrahlen. Als Licht wird nur der sichtbare Teil des elektromagnetischen Sp...

Die DNA liegt in einer genau definierten Kopienzahl pro Zelle vor und ist chemisch und physikalisch relativ stabil, wodurch auch die Analyse von stark verarbeiteten Produkten, die beispielsweise thermisch behandelt wurden, möglich ist. Grundsätzlich muss vor jeder molekularbiologischen Analyse die zugrunde liegende DNA aus dem zu untersuchenden Leb...

Elektrophoretische Verfahren nutzen die Wanderung von geladenen Teilchen im elektrischen Feld als Messgröße. Aufgrund ihrer unterschiedlichen Ladungen und molaren Massen, wandern die Teilchen unterschiedlich schnell und können dadurch voneinander getrennt werden. Bei der Untersuchung von Nucleinsäuren ist die Agarose-Gelelektrophorese zu einem fest...

Lebensmittel enthalten neben den eigentlichen Hauptbestandteilen, die vornehmlich für den Energiestoffwechsel des Körpers von Bedeutung sind, auch Bestandteile – hier als spezielle Inhaltsstoffe bezeichnet, die oftmals erst den besonderen (Genuss-)Wert eines Erzeugnisses ausmachen bzw. zur Beurteilung eines Produktes herangezogen werden können. Die...

Die Basisuntersuchung von Lebensmitteln und ihren Rohstoffen umfasst neben den eigentlichen wertbestimmenden Hauptbestandteilen wie Fett, Eiweiß und Kohlenhydraten sowie speziellen Inhaltsstoffen auch die Bestimmung allgemeiner Kenngrößen. Bei den allgemeinen Kenngrößen handelt es sich vornehmlich um Summenparameter von Major- bzw. Minorkomponenten...

Flavocoenzymes are nearly ubiquitous cofactors that are involved in the catalysis and regulation of a wide range of biological processes including some light-induced ones, such as the photolyase-mediated DNA repair, magnetoreception of migratory birds, and the blue-light driven phototropism in plants. One of the factors that enable versatile flavin...

Safety along the food and feed supply chain is an emerging topic and closely linked to the ability to analytical trace the geographical origin of food or feed. In this study, ultra-performance liquid chromatography coupled with electrospray ionization quadrupole-time-of-flight mass spectrometry was used to trace back the geographical origin of 151...

Aptamers feature a number of advantages, compared to antibodies. However, their application has been limited so far, mainly because of the complex selection process. ‘High-throughput sequencing fluorescent ligand interaction profiling’ (HiTS–FLIP) significantly increases the selection efficiency and is consequently a very powerful and versatile tec...