Markus Fischer

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

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...

Counterfeiting is an omnipresent issue, among others in the cosmetics industry or on the art market. Particularly in the case of very expensive perfumes or very valuable art objects, counterfeits are strongly represented and are steadily increasing. Typically, the content of perfumes is analyzed, but the bottle offers another level of authenticatio...

This proof-of-principle study describes the development of a rapid and easy-to-use DNA microarray assay for the authentication of giant tiger prawns and whiteleg shrimp. Following DNA extraction and conventional end-point PCR of a 16S rDNA segment, the PCR products are hybridised to species-specific oligonucleotide probes on DNA microarrays located...

High price differences between European (e.g., from Italy) and Caucasian (e.g., from Georgia) cultivars motivate food fraud in hazelnuts. In this work, we present two targeted methods for differentiation and grouping different hazelnut cultivars based on polymorphic variations in the chloroplast genome. After sequencing the chloroplast genome of 12...

Chemical decomposition of DMSO stock solutions is a common incident that can mislead biological screening campaigns. Here, we share our case study of 2‐aminothiazole 1, originating from an antimalarial class that undergoes chemical decomposition in DMSO at room temperature. As previously measured biological activities observed against Plasmodium fa...

In the search for new antibacterial compounds, we repositioned an antimalarial compound class by derivatising it based on the so-called "eNTRy" rules for enhanced accumulation into Gram-negative bacteria. We designed, synthesised and evaluated a small library of amino acid modified compounds together with the respective Boc-protected analogues, lea...

The determination of the geographical origin of wood can be highly relevant for several reasons: On the one hand, it can help to prevent illegal logging and timber trade, on the other hand, it is of special interest for archaeological artefacts made of wood, as well as for a variety of biological questions. For this reason, different extraction met...

The aim of the present study was the prediction of the geographical origin of almonds (Prunus dulcis Mill.) via Fourier transform near-infrared (FT-NIR) spectroscopy. For this purpose, 250 almond samples from six different countries were analyzed. As the year of harvest has a major impact on the metabolome, three different crop years (2017–2019) we...

Bei der Analyse von Lebensmitteln stellen sich zu Beginn stets die gleichen Fragen: Was soll wie, wann und warum untersucht werden und was bedeuten die Ergebnisse? Entlang dieser Fragestellungen liefert dieses Lehrbuch einen praxisorientierten Leitfaden, der sämtliche Themengebiete der Lebensmittelanalytik umfasst und systematisch wiedergibt. Hie...

Walnuts, with their health-promoting ingredients, are among the most popular nuts, and practicable methods for determining their geographical origin are needed to tackle food fraud. Authentic walnut samples (235, Juglans Regia L.) from different harvest years (2016–2019) and countries were analyzed by 1H NMR spectroscopy in combination with chemome...

The prices of walnuts vary according to their geographical origin and, therefore, offer a financial incentive for adulteration. A reliable analysis method is required to quickly detect possible misdeclarations and thus prevent food fraud. In this study, a method to distinguish between seven geographical origins of walnuts using Fourier transform ne...

To counteract food fraud, this study aimed at the differentiation of walnuts on a global and regional level using an isotopolomics approach. Thus, the multi-elemental profiles of 237 walnut samples from ten countries and three years of harvest were analyzed with inductively coupled plasma mass spectrometry (ICP-MS), and the resulting element profil...

Food authenticity concerning the geographical origin becomes increasingly important for consumers, food industries, and food authorities. In this study, nontargeted1H NMR metabolomics combined with machine learning methodologies was applied to successfully distinguish the geographical origin of 237 samples of white asparagus from Germany, Poland, T...

Experiments based on metabolomics represent powerful approaches to the experimental verification of the integrity of food. In particular, high-resolution non-targeted analyses, which are carried out by means of liquid chromatography-mass spectrometry systems (LC-MS), offer a variety of options. However, an enormous amount of data is recorded, which...

Flavoproteins are important blue light sensors in photobiology and play a key role in optogenetics. The characterization of their excited state structure and dynamics is thus an important objective. Here we present a detailed study of excited state vibrational spectra of flavin mononucleotide (FMN), in solution and bound to the LOV-2 (Light-Oxygen-...

Truffles are certainly the most expensive mushrooms; the price depends primarily on the species and secondly on the origin. Because of the price differences for the truffle species, food fraud is likely to occur, and the visual differentiation is difficult within the group of white and within the group of black truffles. Thus, the aim of this study...

This special issue of the JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY contains a collection of papers on the authenticity of food.

The aim of this study was to develop a protocol for the authentication of truffles using ICP-MS. The price of the different truffle species varies significantly, and since the visual differentiation is difficult within the white and within the black truffles, food fraud is likely to occur. Thus, in the context of this work, the elemental profiles o...

The addition of cheap and readily available raw materials, such as peanut powder, to visually and chemically similar matrices is a common problem in the food industry. When peanuts are used as adulterant, there is an additional risk of potential health hazard to consumers due to allergy-induced anaphylaxis. In this study, different series of peanut...

Many plant metabolism processes are currently not completely understood despite the numerous studies. These include the events in plant shoots and especially in the apical meristem. To understand the various mechanisms on a molecular level, a combined approach of target and non-targeted fingerprinting analysis was worked out on different white aspa...

Truffles are hypogeous fungi mainly found in Europe and Asia. Due to their special aroma and taste, some truffle species are sold on the international market at an extremely high price. Among the economically relevant species, the white Alba truffle (Tuber magnatum) and the black Périgord truffle (T. melanosporum) are the most appreciated species....