Karl Speer

The lipid fraction of the coffee bean

The lipid fraction of coffee is composed mainly of triacylglycerols, sterols and tocopherols, the typical components found in all common edible vegetable oils. Additionally, the so-called coffee oil contains diterpenes of the kaurene family in proportions of up to 20 % of the total lipids. Diterpenes are of interest because of their analytical and physiological effects. The composition of the main lipid components of the two most important coffee species, Coffea arabica and Coffea canphora var. Robusta is presented. In addition, the influences of typical processes like roasting and steaming on selected lipid components as well as the effects of the storage of green coffee beans under different conditions will be described. Furthermore, new findings regarding the 5-hydroxytryptamides, the main parts of the coffee wax located on the outer layer of the bean and the recently identified components coffeadiol and arabiol I will also be discussed.

Classification and Characterization of Manuka Honeys Based on Phenolic Compounds and Methylglyoxal

Manuka honey from New Zealand is often considered to be a medicinal product of special value due to its high level of antimicrobial activity. Therefore, the distinct authentication of its botanical origin is of great importance. Aside from the common pollen analysis, it is in this respect particularly the analysis of the phenolic acids, flavonoids, and norisoprenoids that is described as useful. In the present study, numerous manuka honeys were analyzed by UPLC-PDA-MS/MS after solid-phase extraction and compared to other kinds of honey to define marker substances characteristic for manuka honeys. The PDA profiles obtained differed markedly from each other so that the individual honey samples could be assigned to three groups. For the honeys of group 1 the comparably high concentrations of 4-hydroxybenzoic acid, dehydrovomifoliol, and benzoic acid proved to be typical, whereas the profiles of group 2 showed high kojic acid and 2-methoxybenzoic acid intensities. The manuka honeys of group 3, on the other hand, yielded high amounts of syringic acid, 4-methoxyphenyllactic acid, and methyl syringate. Furthermore, the comprehensive comparison of manuka honeys to other unifloral honeys revealed that especially kojic acid, 5-methyl-3-furancarboxylic acid, leptosin, unedone, 2-methoxybenzoic acid, 4-methoxyphenyllactic acid, 3-hydroxy-1-(2-methoxyphenyl)penta-1,4-dione, and methyl syringate were useful for distinguishing manuka honeys from the other kinds of investigated honeys. Moreover, kojic acid, unedone, 5-methyl-3-furancarboxylic acid, 3-hydroxy-1-(2-methoxyphenyl)penta-1,4-dione, and lumichrome were identified in manuka honey for the first time.

Gas chromatography-mass spectrometry (GC-MS) method for the determination of 16 European priority polycyclic aromatic hydrocarbons in smoked meat products and edible oils

A gas chromatography-mass spectrometry (GC-MS) method was developed for the analysis of 15 polycyclic aromatic hydrocarbons (PAHs) highlighted as carcinogenic by the Scientific Committee on Food (SCF) plus benzo[c]fluorine (recommended to be analysed by the Joint FAO/WHO Expert Committee on Food Additives (JECFA)) in fat-containing foods such as edible oils and smoked meat products. This method includes accelerated solvent extraction (ASE) and the highly automated clean-up steps gel permeation chromatography (GPC) and solid-phase extraction (SPE). Using a VF-17ms GC column, a good separation of benzo[b]fluoranthene, benzo[j]fluoranthene and benzo[k]fluoranthene was achieved. Furthermore, the six methylchrysene isomers and the PAH compounds with a molecular weight of 302 Daltons in fat-containing foods attained a better chromatographic separation in comparison with a 5-ms column. The reliability of the analytical method for edible oils was demonstrated by the results from a proficiency test. Measurements with GC-high-resolution mass spectroscopy (HRMS) and gas chromatography-mass selective detection (GC-MSD) led to comparable results. A survey of the 16 PAHs in 22 smoked meat products showed concentrations in the range <0.01–19 µg kg−1. The median concentration for benzo[a]pyrene was below 0.15 µg kg−1.

Assessment of sample cleanup and matrix effects in the pesticide residue analysis of foods using postcolumn infusion in liquid chromatography-tandem mass spectrometry.

Matrix effect profiles can be used to visualize the effect of the sample matrix to the data signals occurring in a chromatogram. In the present study these profiles were generated by postcolumn infusion of a standard pesticide mix with extracts of different food matrices prepared by the QuEChERS method. Complete raw extracts as well as individual clean-up steps were analyzed. This allowed for a detailed comparison of the interferences caused by the matrix effects from various food samples. It also gave an idea about the efficiency of matrix reduction processes. When analyzing the individual clean-up extracts of the QuEChERS method just a slight reduction of matrix effects could be observed from step to step. Matrices causing strong signal effects in the results of the raw extracts also have strong effects after the final clean-up step. Some of the components responsible for the matrix effects show an extremely high retention time. After the injection of extracts from rocket or different types of tea, significant ion suppressions occurred even after rinsing the analytical column for a long time. The experiments have shown that similar matrices can produce different matrix effect profiles. For example, for black teas and green teas significantly different matrix effect profiles were obtained, while the matrix effects of teas within one of these groups were exactly the same. Analogous results could be found for citrus fruits. In order to overcome interfering matrix effects, analytical systems equipped with different electrospray ion sources were tested. Furthermore, profiles of diluted food extracts were generated. Dilution led to a significant decrease in the matrix effects.

Development and validation of an efficient automated method for the analysis of 300 pesticides in foods using two-dimensional liquid chromatography-tandem mass spectrometry.

In this study, a fully automated system was developed for the determination of more than 300 different pesticides from various food commodities. The samples were extracted with acetonitrile prior to the injection into the two-dimensional LC-system. No manual clean-up was needed. The separation of analytes and matrix compounds was carried out by a YMC-Pack Diol (2.1 mm×100 mm; 5 μm; 120Å) HILIC column in the first dimension. All analytes eluted within one small fraction at the beginning of the run. With a packed loop interface this fraction was transferred to the analytical reversed phase separation performed on an Agilent Poroshell 120 EC-C18 (2.1 mm×100 mm; 2.7 μm; 120Å). Some very polar compounds with a stronger retention on the HILIC column were measured directly. The method was validated for over 300 pesticides in cucumber, lemon, wheat flour, rocket, and black tea. For the large majority of the analytes, the recovery was between 70% and 120% and the relative standard deviation was clearly under 20%. The limits of detection for nearly all the compounds were at least at 0.01 mg/kg. For over 50% of the analytes, good sensitivity was observed even at 0.001 mg/kg. In spite of the injection of a pure sample extract, the method showed robust results even with dirty matrices like hops and tea.

Fast‐GC/HRMS to quantify the EU priority PAH

For the analysis of the 15 polycyclic aromatic hydrocarbons (PAH) classified as priority from the Scientific Committee on Food (SCF) and benzo[c]fluorene (BcL) assessed to be relevant by the Joint FAO/WHO Experts Committee on Food Additives (JECFA) in food, a sensitive analytical method is necessary. In the past, many methods were established for only the analysis of the 16 priority PAH recommended by the US Environmental Protection Agency (16 EPA-PAH) but not for the 15 SCF-PAH and BcL. Therefore, at the Max-Rubner-Institut, Federal Research Institute of Nutrition and Food in Kulmbach, Germany, an analytical method with a runtime of 72 min was developed. To shorten this runtime without a loss of separation, a Fast-GC/high resolution MS (HRMS) method with a runtime of only 25 min using a TR-50ms column (10 m x 0.1 mm x 0.1 microm) was created. The repeatability (n = 3) of spiked PAH concentrations in test-matrix tea ranged from 0.1 to 11%. The analytical parameters LOD (0.01-0.02 microg/kg) and LOQ (0.03-0.06 microg/kg) also in the test-matrix tea were determined. A good linearity for all PAH (R(2) >0.99) and averaged recoveries from 75 to 117% in the concentration range of 1-20 microg/kg were achieved.

Confirmation of phenolic acids and flavonoids in honeys by UPLC-MS

Certain phenolic acids and flavonoids are described in the literature as marker substances for several unifloral honeys. As not all authors utilised the same methods for extraction and determination, there are remarkable discrepancies in the published data concerning these substances. Ethyl acetate extracts which, aside from phenolic acids, also contain flavonoids were analysed by Ultra Performance Liquid Chromatography-Quadrupole/Time of flight-mass spectrometry (UPLC-Q/TOF-MS). First, the mass spectra of 37 phenolic acids and flavonoids described in the literature were recorded. Consequently, sunflower honeys, lime honeys, clover honeys, rape honeys, and honeydew honeys were analysed in regard to these substances. By employing the ChromaLynx™ software, 34 of the 37 substances were identified quickly and clearly. By combining the retention time and the accurate molecular mass, it was even possible to identify several compounds which cannot be detected by diode array detection.ZusammenfassungFür die Authentifizierung der Sortenhonige sind insbesondere solche Indikatorverbindungen von Interesse, die direkt mit dem Nektar in Verbindung gebracht werden können. Mit unterschiedlichsten Extraktionsmethoden und Analysenverfahren in der Literatur beschriebene Phenolcarbonsäuren und Flavonoide wurden in Tabelle I zusammengefasst. Anschließend wurden Ethylacetatextrakte von fünf Honigsorten (4 Sonnenblumen-, 3 Linden-, 3 Klee-, 5 Raps- und 4 Waldhonige) auf das Vorkommen dieser Verbindungen mit einer Ultra Performance Liquid Chromatography (UPLC)-Anlage gekoppelt mit einem Time-of-flight-Massenspektrometer (TOF-MS) untersucht. Mit der automatisierten Auswertungssoftware ChromaLynx™ konnten 34 der 37 gelisteten Verbindungen innerhalb weniger Minuten eindeutig identifiziert werden, obwohl es durch die gekürzte Analysenzeit auf 20 Minuten (s. Abb. 3 im Gegensatz zu Abb. 4) zu zahlreichen Überlagerungen von bekannten als auch unbekannten Verbindungen kam. Aufgrund gleicher Aufarbeitung und gleicher Injektionsvolumina konnten die Honige vergleichend semi-quantitativ ausgewertet werden (s. Tab. I).Honige einer Sorte zeigten vergleichbare Phenolprofile, in denen auch die Verhältnisse der einzelnen Verbindungen zueinander sehr ähnlich waren. Neben der eindeutig identifizierten Hydrozimtsäure (s. Abb. 5), die eine Markerverbindung für Rapshonig ist (Steeg und Montag, 1988b) und von Abscisinsäure überlagert wurde, konnten weitere wenig UV-sensitive Verbindungen wie β-Phenylmilchsäure (s. Abb. 3 und Abb. 4) und Mandelsäure mittels TOF-MS und negativer ElectroSprayIonisation (ESI) detektiert werden. Die Abbildungen 1–3 belegen zudem, dass eine Unterscheidung der Honigsorten über die phenolischen Verbindungen möglich ist, da sich die Verteilung als auch die Gewichtung der einzelnen Substanzen stark unterscheiden. Durch die Selektivität und Sensitivität des Quadrupol/Time-of-flight (Q/TOF)-Detektors war es nicht nur möglich, alle bekannten Substanzen zu erfassen, sondern auch alle aus dem Honig extrahierten Verbindungen. Durch die Angabe der genauen Masse, für die die Software eine mögliche Summenformel vorschlägt, ist damit die Suche und Identifizierung nach möglichen sortenspezifischen, noch unbekannten Markerverbindungen erheblich erleichtert. An der Identifizierung markanter Peaks aus Linden-, Raps- und Waldhonig wird zurzeit gearbeitet. Da einige Verbindungen besser durch Massenspektrometrie erfasst werden können als über DAD, wird eine quantitative Auswertung über HPLC-MS/MS empfohlen.

Polycyclic aromatic hydrocarbons (PAH) and phenolic substances in meat products smoked with different types of wood and smoking spices

The contents of polycyclic aromatic hydrocarbons (15+1 EU PAH) and phenolic substances (guaiacol, 4-methylguaiacol, syringol, eugenol, and trans-isoeugenol) were investigated in smouldering-smoked Frankfurters and mini-salamis. For the 51 smoking experiments wood chips of oak, poplar, hickory, spruce, fir, alder, beech, and beech with an apple-smoking spice mix, cherry-smoking spice mix, and a mix of juniper berries and bay leaves were tested. The use of poplar and hickory led to a decrease in the PAH contents in the range of 35-55% compared to the commonly used beech wood. Higher PAH contents by using softwood were not observed. The use of the rapidly growing poplar seems to be a reasonable approach for reducing the PAH contents in smoked meat products. Furthermore, the sum contents of the five phenolic substances in sausages smoked with poplar were higher, or only slightly lower, when compared to the use of beech.

Contents of polycyclic aromatic hydrocarbons (PAH) and phenolic substances in Frankfurter-type sausages depending on smoking conditions using glow smoke

The contents of polycyclic aromatic hydrocarbons (PAH) and phenolic substances in Frankfurter-type sausages were investigated depending on hot smoking conditions (glow smoke). For the 24 smoking experiments (performed in duplicates) three different smoke densities and ventilator velocities as well as wood chips with five different moisture contents were tested. During the smoking process, concentrations of O(2), CO(2) and CO, humidity and temperature in the smoking chamber as well as smoke generation temperature were determined. The chemical analysis included the contents of the 15+1 EU priority PAH and the phenolic substances guaiacol, 4-methylguaiacol, syringol, eugenol and trans-isoeugenol. The smoking conditions had a significant influence on smoke generation temperature, organoleptic properties and the formation of PAH and phenolic substances. The PAH contents increased with smoke density and ventilator velocity. No correlation between the contents of PAH and phenols was observed.

Pesticide residues in chicken eggs - A sample preparation methodology for analysis by gas and liquid chromatography/tandem mass spectrometry.

A sample preparation method was developed for the analysis of chicken eggs to determine 97 GC and 81 LC amenable residues, including organophosphates, organochlorines, pyrethroids, triazoles, carboxyl-containing compounds, and the indicator PCBs. Hereby, considerations were given to the recoveries of the analytes, the methods suitability for routine analysis, and the assessment of the clean-up effect, for which a simple thin layer chromatography was implemented to visualize the most important lipid classes. The procedure consisted of (I) the extraction by matrix solid phase dispersion, and the clean-up by means of (II) small-scale gel permeation chromatography (GPC) and (III) two different solid phase extractions (SPE) for GC and LC amenable analytes, as well as (IV) the quantification using GC-MS/MS and LC-MS/MS. Cyclohexane/ethyl acetate was chosen as extraction solvent due to its suitability for extracting strong non-polar but also more polar analytes. The classical GPC was scaled down to ensure a 50% lower solvent consumption. The comprehensive investigation of conventional and modern zirconium-oxide-coated SPE materials resulted in the selection of octadecyl-modified silica (C18) combined with primary secondary amine using acetonitrile as elution solvent for GC amenable analytes and pure C18 in combination with acidified methanol for LC amenable pesticides. Compared to the currently established EN 1528 method the sample preparation proposed offered a higher sample throughput and a lower solvent consumption. Furthermore, for the first time the clean-up effectiveness of the sample preparation steps was documented as shown by means of thin-layer chromatography. The validation of chicken eggs proved the fulfillment of the quality control criteria for 164 of the 178 analytes tested, mostly at the lowest validated level of 5μg/kg for pesticides and 0.5μg/kg for the single indicator PCBs. However, the analysis of strongly polar analytes was still problematic, which could be attributed to the extraction and the GPC step. Nevertheless, the successful investigation of EU proficiency test materials (EUPT AO 07-09) confirmed the comparability of the results with the currently established sample preparation procedures and demonstrated the potential of the applicability of the presented method to other matrices as exemplified for lean poultry meat and fatty liquid cream.