Hans-Georg Schmarr

Technische Universität München, München, Bavaria, Germany

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Publications (35)97.06 Total impact

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    ABSTRACT: Skatole metabolites have been considered as putative contributors to boar taint. Recently, 2-aminoacetophenone, a volatile phase I skatole metabolite, was identified in back fat samples from boars of Pietrain × Baden-Württemberg hybrid type. This report addresses the question of the physiological origin of the observed 2-aminoacetophenone in these pigs. Microsomal fractions from nine boars were isolated and formation of skatole metabolites was subsequently analyzed by stable-isotope dilution analysis (SIDA) using headspace solid-phase microextraction gas chromatography/mass spectrometry (HS-SPME−GC/MS). Significant breed-related differences in phase I skatole metabolism were observed explaining the high levels of 2-aminoacetophenone in Pietrain × Baden-Württemberg hybrid type boars.
    No preview · Article · Jan 2016 · Journal of Agricultural and Food Chemistry
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    ABSTRACT: Trace-level analysis of cork off-flavor compounds considered as responsible for typical [2,4,6-trichloroanisole (TCA)] and atypical cork taint [geosmin (GSM); 2-methylisoborneol (MIB); 3-isopropyl-2-methoxypyrazine (IPMP); 3-isobutyl-2-methoxypyrazine (IBMP); 3,5-dimethyl-2-methoxypyrazine (MDMP)] was achieved for cork soaks and wines for concentrations below odor threshold (MIB only in cork soaks). The analytical approach was based on headspace solid-phase microextraction and heart-cut multidimensional gas chromatography with tandem mass spectrometric detection. Quantification was done using a stable isotope dilution assay. Individual cork stoppers with varying sensory off-odor descriptions were analyzed. In particular, IPMP and IBMP correlated with the cork stoppers described with green attributes. MDMP was found in samples described as dusty–musty or nutty-like. In a migration study, transport of off-flavor compounds from affected cork stoppers into the corresponding wine could be observed after a storage period of 13 months. Multivariate statistics on the wines’ sensory analysis and chemical data showed a good correlation of the individual off-flavor compound concentration, its sensory description and the off-flavor perceived in the wine.
    No preview · Article · Dec 2015 · European Food Research and Technology
  • Petra Slabizki · Claus Fischer · Charlotte Legrum · Hans-Georg Schmarr
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    ABSTRACT: Natural cork stoppers with sensory deviations other than the typical cork taint were sub-grouped according to their sensory descriptions and compared with unaffected control cork stoppers. The assessment of purge and trap extracts obtained from corresponding cork soaks was performed by heart-cut multidimensional gas chromatography olfactometry (MDGC-O). The identification of compounds responsible for untypical cork taint detected in MDGC-O was further supported with additional multidimensional GC analysis in combination with mass spectrometric detection. Geosmin and 2-methylisoborneol were mainly found in cork stoppers described as moldy and cellar-like; 3-isopropyl-2-methoxypyrazine and 3-isobutyl-2-methoxypyrazine in cork stoppers described with green attributes. Across all cork sub-groups the impact compound for the typical cork taint, 2,4,6-trichloroanisole (TCA), was present and is therefore a good marker for cork taint in general. Another potent aroma compound, 3,5-dimethyl-2-methoxypyrazine (MDMP), was also detected in each sub-group obviously playing an important role with regard to the untypical cork taint. Sensory deviations possibly affecting the wine could be generated by MDMP and its presence should thus be monitored in a routine quality control.
    No preview · Article · Aug 2015 · Journal of Agricultural and Food Chemistry
  • Christof Björn Steingass · Reinhold Carle · Hans-Georg Schmarr
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    ABSTRACT: Qualitative ripening-dependent changes of pineapple volatiles were studied via headspace solid-phase microextraction and analyzed by comprehensive two-dimensional gas chromatography quadrupole mass spectrometry (HS-SPME-GC×GC-qMS). Early green-ripe stage, post-harvest ripened, and green-ripe fruits at the end of their commercial shelf-life were compared to air-freighted pineapples harvested at full maturity. In total, more than 290 volatiles could be identified by mass spectrometry and their linear retention indices. The majority of compounds comprise esters (methyl and ethyl esters of saturated and unsaturated fatty acids, acetates), terpenes, alcohols, aldehydes, 2-ketones, free fatty acids, and miscellaneous γ- and δ-lactones. The structured separation space obtained by GC×GC allowed revealing various homologous series of compound classes as well as clustering of sesquiterpenes. Post-harvest ripening increased the diversity of the volatile profile compared to both early green-ripe maturity stages and on-plant ripened fruits.
    No preview · Article · Feb 2015 · Analytical and Bioanalytical Chemistry
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    ABSTRACT: Ripening-dependent changes of pineapple volatiles were studied in a nontargeted profiling analysis. Volatiles were isolated via headspace solid phase microextraction and analyzed by comprehensive 2D gas chromatography and mass spectrometry (HS-SPME-GC×GC-qMS). Profile patterns presented in the contour plots were evaluated applying image processing techniques and subsequent multivariate statistical data analysis. Statistical methods comprised unsupervised hierarchical cluster analysis (HCA) and principal component analysis (PCA) to classify the samples. Supervised partial least squares discriminant analysis (PLS-DA) and partial least squares (PLS) regression were applied to discriminate different ripening stages and describe the development of volatiles during postharvest storage, respectively. Hereby, substantial chemical markers allowing for class separation were revealed. The workflow permitted the rapid distinction between premature green-ripe pineapples and postharvest-ripened sea-freighted fruits. Volatile profiles of fully ripe air-freighted pineapples were similar to those of green-ripe fruits postharvest ripened for 6 days after simulated sea freight export, after PCA with only two principal components. However, PCA considering also the third principal component allowed differentiation between air-freighted fruits and the four progressing postharvest maturity stages of sea-freighted pineapples.
    Preview · Article · Feb 2015 · Analytical and Bioanalytical Chemistry
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    ABSTRACT: Headspace solid phase microextraction and chirospecific gas chromatography–mass spectrometry in selected ion monitoring mode (HS-SPME–GC–SIM-MS) allowed quantitative determination of δ-lactones (δ-C8, δ-C10) and γ-lactones (γ-C6, γ-C8, γ-C10). A stable isotope dilution assay (SIDA) with d7-γ-decalactone as internal standard was used for quantitative analysis of pineapple lactones that was performed at three progressing post-harvest stages of fully ripe air-freighted and green-ripe sea-freighted fruits, covering the relevant shelf-life of the fruits. Fresh pineapples harvested at full maturity were characterised by γ-C6 of high enantiomeric purity remaining stable during the whole post-harvest period. In contrast, the enantiomeric purity of γ-C6 significantly decreased during post-harvest storage of sea-freighted pineapples. The biogenetical background and the potential of chirospecific analysis of lactones for authentication and quality evaluation of fresh pineapple fruits are discussed.
    No preview · Article · Feb 2015 · Food Chemistry

  • No preview · Chapter · Dec 2014
  • Petra Slabizki · Theodoros Potouridis · Hans-Georg Schmarr
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    ABSTRACT: During the enantioselective analysis of whisky lactones after headspace in-tube extraction and gas chromatography with mass spectrometric detection using an ion trap mass analyzer (ITMS), an unusual effect led to peak suppression for one of the four enantiomers of whisky lactones. Using the ITMS in the selective ion monitoring (SIM) mode, one of the four targeted whisky lactone enantiomers could not be detected due to an abundant co-eluting matrix compound. For troubleshooting, detection with a quadrupole MS proved the presence of the missing enantiomer peak. A hypothetical explanation of this phenomenon is at present based on the different ion scanning mechanism of the two MS instruments. Considering the irregular sampling during the discontinuous scanning process of the ITMS being dictated by the ion current, this might have led to the suppression of the analyte. Furthermore, a solvent trapping effect of the target analyte with a co-chromatographing abundant matrix compound created a peak distortion (focusing) of the minor whisky lactone enantiomer. In our case, the inexplicably missing enantiomer peak triggered this investigation, but such matrix effects could easily be overseen with ITMS (SIM) detection, then eventually causing false-negative results.
    No preview · Article · Dec 2014 · Chromatographia
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    ABSTRACT: A method for trace-level analysis of 3-alkyl-2-methoxypyrazines (MPs) based on mixed-bed cation-exchange solid phase extraction followed by heart-cut multidimensional gas chromatographic analysis was applied in a trial on viticultural and enological treatments of Sauvignon blanc wines produced in Germany. The quantification was based on a stable isotope dilution assay using deuterated MPs. For method comparison, detection was either with selected ion monitoring with a quadrupole mass spectrometer (MS) or after selected reaction monitoring using a triple quadrupole MS. Comparable performance for MP detection in the lower ng L-1 concentration range was found for both detection methods; however, in some cases, matrix problems could only be solved with MS/MS detection. It could be shown that MP levels varied considerably between the investigated vintages, with concentrations often well below 10 ng L-1. Leaf removal as a viticultural trial was a measure to decrease MP concentrations; however, the effects observed were low in the vintages studied here. Cold maceration and stem addition to the must were found as valuable enological means for increasing the MP concentration and improving the green sensory notes typical for cold climate Sauvignon blanc wines.
    Full-text · Article · Oct 2014 · European Food Research and Technology
  • Charlotte Legrum · Petra Slabizki · Hans-Georg Schmarr
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    ABSTRACT: With respect to the current hypothesis that natural amino acids may serve as starting material for the biosynthesis of alkyl-methoxypyrazines, the enantiomeric distribution of the potent aroma compound 3-sec-butyl-2-methoxypyrazine (SBMP) was determined in various species using heart-cut multidimensional gas chromatography (H/C MDGC) or comprehensive two-dimensional gas chromatography (GC × GC). Complementary to an earlier described separation on octakis-(6-O-methyl-2,3-di-O-pentyl)-γ-cyclodextrin used as chiral stationary phase, we found a reversal of the elution order of SBMP enantiomers on heptakis-(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin, providing further confirmation options for that type of analysis. Optimization of the enantioseparation of SBMP in a single-oven H/C enantio-MDGC system involved the use of a dual-jet cryo modulator for trapping of analytes transferred from the achiral 1D column to the chiral 2D column before starting the 2D enantioseparation with an independent temperature ramp. For the enantiodifferentiation by enantio-GC × GC, the modulation period had to be significantly shortened to avoid loss of chiral resolution gained in 1D. H/C MDGC with mass spectrometric detection (MS) using selected ion monitoring (SIM) was sufficient for parts per billion level analysis, whereas H/C MDGC-MS/MS or GC × GC time-of-flight (TOF) MS were necessary for parts per trillion level analysis. In various vegetables, lady beetles and Vitis vinifera species analyzed, only (S)-SBMP was detected, supporting the hypothesis of natural amino acids serving as starting material for the biosynthesis of alkyl-methoxypyrazines. Graphical Abstract Harmonia axyridis analyzed using headspace solid phase microextraction and enantio-GC × GC-TOF-MS
    No preview · Article · Aug 2014 · Analytical and Bioanalytical Chemistry
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    Petra Slabizki · Charlotte Legrum · Reinhard Meusinger · Hans-Georg Schmarr
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    ABSTRACT: The three constitutional isomers of dimethyl-substituted methoxypyrazines: 3,5-dimethyl-2-methoxypyrazine 1; 2,5-dimethyl-3-methoxypyrazine 2; and 2,3-dimethyl-5-methoxypyrazine 3 are potent flavor compounds with similar mass spectrometric, gas chromatographic, and nuclear magnetic resonance spectroscopic behavior. Therefore, unambiguous analytical determination is critical, particularly in complex matrices. The unequivocal identification of 1-3 could be achieved by homo- and heteronuclear NMR correlation experiments. The observed mass fragmentation for 1-3 is proposed and discussed, benefitting from synthesized partially deuterated 1 and 2. On common polar and apolar stationary phases used in gas chromatography (GC) 1 and 2 show similar behavior whereas 3 can be separated. In our focus on off-flavor analysis with respect to wine aroma, 1 has been described as a "moldy" off-flavor compound in cork and 2 as a constituent in Harmonia axyridis contributing to the so-called "ladybug taint," whereas 3 has not yet been described as a constituent of wine aroma. A successful separation of 1 and 2 could be achieved on octakis-(2,3-di-O-pentyl-6-O-methyl)-γ-cyclodextrin as stationary phase in GC. Applying heart-cut multidimensional GC analysis with tandem mass spectrometric detection we could confirm the presence of 1 as a "moldy" off-flavor compound in cork. However, in the case of Harmonia axyridis, a previous identification of 2 has to be reconsidered. In our experiments we identified the constitutional isomer 1, which was also found in Coccinella septempunctata, another species discussed with respect to the "ladybug taint." The analysis of such structurally related compounds is a demonstrative example for the importance of a chromatographic separation, as mass spectrometric data by itself could not guarantee the unequivocal identification.
    Preview · Article · Aug 2014 · Analytical and Bioanalytical Chemistry
  • Ulrich Fischer · Doreen Schober · Michael Wacker · Hans-Georg Schmarr

    No preview · Conference Paper · Aug 2014
  • Hans-Georg Schmarr · Johannes Langen · Charlotte Legrum · Petra Slabizki

    No preview · Conference Paper · Aug 2014
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    ABSTRACT: Major objective of the presented study was to evaluate whether the hepatic skatole metabolite 2-aminoacetophenone (2-AAP) is a potential contributor to boar taint, being an undesired off-flavor in pork. Therefore, backfat samples were screened by HS-SPME–GC/MS revealing a significant accumulation of the hepatic skatole metabolite 2-AAP in boar fat. Subsequently, a stable-isotope dilution assay (SIDA) was elaborated to precisely quantitate 2-AAP in a set of 130 backfat samples. The observed concentrations ranged between 34 ng/g and 1178 ng/g, resulting in a mean value of 100 ng/g. In addition, the odor detection threshold of 2-AAP was evaluated by a trained sensory panel using a single-staircase, triple forced choice paradigm. The determined 2-AAP odor detection threshold is similar to the thresholds of the major boar taint compounds androstenone and skatole. Finally, a sensory evaluation of backfat samples spiked with 2-AAP was performed in a triangle test with untrained testers. Here, the 2-AAP spiked samples were frequently identified as the odd sample independent of their respective androstenone and skatole level. In conclusion, the hepatic skatole metabolite 2-AAP was identified as a potential contributor to boar taint.
    No preview · Article · Aug 2014 · Food Research International
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    ABSTRACT: Pineapples are highly valued tropical fruits appreciated by many consumers due to their exotic aroma impression. However, fully ripe fruits are exclusively available as a premium niche product, as they are to be exported by rapid cargo-planes. In contrast, the major proportion of pineapples offered on European markets is harvested at a premature green-ripe stage, since their mechanical and microbial stability allows cheaper fruit logistics by cargo ships. Consequently, sea-freighted fruits need to be post-harvest ripened for flavour development; however, differ in their volatile “profiles” compared to fruits harvested at full maturity [1]. In the presented study, HS-SPME-GC×GC-qMS profiles of four progressing post-harvest maturity stages of green-ripe pineapples were compared to fully ripe air-freighted fruits. The majority of more than 300 compounds identified were esters. The structured separation space obtained by GC×GC with clustering of compound classes as well as extracted ion contour plots of unique mass traces facilitated the identification of volatiles even though mass spectral reference data was unavailable. Profile patterns presented in the contour plots were subsequently analyzed in an unbiased fingerprinting approach applying image processing techniques and chemometric data analysis [2]. Based on significantly different signals, Hierarchical Cluster Analysis (HCA) and Partial Least Squares Discriminant Analysis (PLS-DA) were performed to explore interdependencies within the volatile “profiles” and discriminate the different maturity stages, respectively. Furthermore, Partial Least Squares (PLS) regression was shown to be an excellent tool to deduce those volatiles being formed during post-harvest storage. As a result of the fingerprint analysis clear-cut discrimination of differently ripened and post-harvest handled pineapple samples was possible. The HS-SPME-GC×GC-qMS analysis of volatiles in combination with multivariate statistical data evaluation allowed the distinction between different pineapple maturity stages, hence being an excellent method to rapidly screen for metabolic changes occurring during post-harvest shelf-life of pineapple and eventually other fruits. References [1] Steingass, C. B. et al., Food Chemistry 150 (2014) 382 [2] Schmarr, H.-G. et al., Journal of Chromatography A 1217 (2010) 565
    No preview · Conference Paper · May 2014
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    ABSTRACT: Aroma relevant γ- and δ-lactones are important flavor compounds in various foodstuffs. Their quantitative determination is essential for evaluating food sensory properties as well as food authenticity studies. High-throughput head-space solid-phase microextraction as sample preparation, separation by capillary gas chromatography coupled with triple stage quadrupole mass spectrometry has been evaluated as the analytical method. Monitoring selected reaction mass fragments allowed sub-µg/L quantification of γ- and δ-lactones in complex wine matrices. Tandem mass spectrometry improves specific detection of γ- and δ-lactones, a prerequisite for reliable quantification at low-µg/L concentration levels in complex wine matrices. Copyright © 2013 John Wiley & Sons, Ltd.
    No preview · Article · Dec 2013 · Rapid Communications in Mass Spectrometry
  • Hans-Georg Schmarr · Petra Slabizki · Charlotte Legrum
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    ABSTRACT: Trace level analyses in complex matrices benefit from heart-cut multidimensional gas chromatographic (MDGC) separations and quantification via a stable isotope dilution assay. Minimization of the potential transfer of co-eluting matrix compounds from the first dimension (1D) separation into the second dimension separation requests narrow cut-windows. Knowledge about the nature of the isotope effect in the separation of labeled and unlabeled compounds allows choosing conditions resulting in at best a co-elution situation in the 1D separation. Since the isotope effect strongly depends on the interactions of the analytes with the stationary phase, an appropriate separation column polarity is mandatory for an isotopic co-elution. With 3-alkyl-2-methoxypyrazines and an ionic liquid stationary phase as an example, optimization of the MDGC method is demonstrated and critical aspects of narrow cut-window definition are discussed. Figure Avoiding chromatographic separation of isotopic standards by fine-tuning the isotope effect allows narrow cut-windows in SIDA based MDGC applications.
    No preview · Article · Jun 2013 · Analytical and Bioanalytical Chemistry
  • Petra Slabizki · Hans-Georg Schmarr
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    ABSTRACT: A robust method for routine quality control of corky off-flavour compounds in wine and cork soak matrices has been established. Based on an automated headspace solid phase microextraction (HS-SPME), the method needs only marginal sample preparation and achieves low (sub-ngL(-1)) trace level detection limits (LODs) for the most relevant off-flavour compounds, such as 2,4,6-trichloroanisole (TCA), 2,3,4,6-tetrachloroanisole (TeCA) and 2,4,6-tribromoanisole (TBA). Particularly for wine matrix, reliable trace level quantification had only been achieved after applying heart-cutting multidimensional gas chromatography (MDGC). Using a halogen-sensitive electron capture detector (ECD) and quantification with a stable isotope dilution assay (SIDA), LODs of 0.1ngL(-1) for TCA, TeCA and TBA could be obtained. Since a SIDA based quantification method is used with a non-mass spectrometric detector, the necessary chromatographic resolution of internal standard and target analyte peaks resulted from the use of highly deuterated [(2)H(5)]-isotopologues.
    No preview · Article · Nov 2012 · Journal of Chromatography A
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    ABSTRACT: The separation of deuterated and non-deuterated compounds in gas liquid partitioning chromatography (GLC) on silicone type stationary phase usually results in the inverse isotope effect. With ionic liquids (ILs) as stationary phase, however, this may show a totally different nature. The inverse isotope effect, in which heavier (deuterated) isotopic compounds (isotopologues) elute earlier, is to be expected when van der Waals (London) dispersion forces play a dominant role in the solute-stationary phase interaction. Such (apolar) interactions seem to play only a minor role when ILs are the stationary phases, leading to only a marginal inverse isotope effect, e.g. for the separation of 2,4,6-trichloroanisole and its [(2)H(5)]-isotopologue on 1,12-di(tripropylphosphonium) dodecane bis(trifluoromethansulfonyl) amide (commercialized as SLB-IL59, Supelco). Indeed, with the most polar stationary phase available (commercialized as SLB-IL111; Supelco), this separation showed a normal isotope effect. Further examples are presented and the nature of the isotope effect observed is discussed.
    No preview · Article · Nov 2012 · Journal of Chromatography A
  • Hans-Georg Schmarr · Karl-Heinz Engel
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    ABSTRACT: Contents and enantiomeric distributions of linalool (3,7-dimethyl-1,6-octadien-3-ol) were investigated in raw and roasted cocoa beans (seeds of Theobroma cacao) of defined origin as well as in commercial products, such as cocoa powders or chocolates. The stereodifferentiation of linalool was achieved by enantioselective multidimensional gas chromatography using heptakis (2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin as chiral stationary phase. Simultaneous steam distillation–extraction at pH 7 allowed sample preparation without racemization of linalool. Cocoa beans contain linalool primarily as (S)-enantiomer. Model experiments and analyses of commercial products such as cocoa powders and chocolates revealed that technological procedures employed in the manufacturing of cocoa products do not result in significant changes of the original enantiomeric distribution of linalool.
    No preview · Article · Nov 2012 · European Food Research and Technology