Norbert Christoph - Academia.edu (original) (raw)
Papers by Norbert Christoph
Analytica Chimica Acta, 2002
2-Aminoacetophenone (AAP) is known as the character impact compound responsible for the so called... more 2-Aminoacetophenone (AAP) is known as the character impact compound responsible for the so called untypical 'aging off-flavor' (UTA) in Vitis vinifera wines. The formation of AAP is caused by an oxidative degradation of the phytohormone indole-3-acetic acid (IAA), triggered by sulfuration after fermentation. Using different radical generating systems (hydroxyl and/or superoxide radical generating systems) it could be shown especially that superoxide radicals are responsible for the formation of AAP. Hereby, a pyrrole ring cleavage of IAA yields 3-(2-formylaminophenyl)-3-oxo-propionic acid (FAPOP), N-formyl-2-aminoacetophenone (FAP), and AAP. Analysis of 32 grape musts and their corresponding wines revealed that wines with a higher superoxide radical scavenger activity are less prone to UTA formation. However, UTA is not correlated with the IAA content of the must or wine. Differences in the release of IAA during fermentation of musts derived from early and late harvested grapes indicate a correlation between the ripeness of the processed grapes, the IAA content at the time of sulfuration, and the UTA formation.
Chemie in Unserer Zeit, 2005
Die Isotopenverhältnisse von Wasser, organischem Material und Spurenelementen aus Lebensmitteln h... more Die Isotopenverhältnisse von Wasser, organischem Material und Spurenelementen aus Lebensmitteln hängen von den Umständen und Orten ihrer Entstehung und Verarbeitung ab. Zu Ihrer quantitativen Analyse stehen die Methoden der massenspektrometrischen Isotopenverhältnisanalyse und der positionellen 2H-Analyse zur Verfügung. In deren Anwendung auf die Untersuchung der Herkunft und der Authentizität von Lebensmitteln werden Beispiele für den Nachweis der Wässerung bzw. der Zuckerung von Wein und Obstsäften beschrieben und die Methoden zur Erkennung eines nicht deklarierten Zusatzes von L-Äpfelsäure und Ascorbinsäure erläutert. Die Multielementisotopenanalyse ermöglicht die Erkennung der Herkunft tierischer Produkte (Eier, Milchprodukte, Fleisch) und die Unterscheidung zwischen natürlichen und naturidentischen Aromastoffen. Schließlich werden die Möglichkeiten der Isotopenverhältnisanalyse zur Unterscheidung von pflanzlichen und tierischen Produkten, die nach konventionellen oder ökologischen Verfahren erzeugt wurden, diskutiert.The correlations between isotope ratios in water, organic mass, and trace elements of food and beverages, and the circumstances and sites of their origin and production are outlined, and the methods of mass spectrometric isotope ratio determination and the positional 2H analysis by quantitative NMR measurement are explained. In context with the application of these methods for origin and authenticity investigations of food, examples are given for the proof of watering or sugar addition to wine and fruit juices and methods for the identification of nondeclared additions of L-malic and Lascorbic acids are described. The possibilities of multielement isotope ratio analysis for the identification of origin of animal products (eggs, milk products, meat) and methods for the discriminations between natural and nature identical aroma compounds are outlined. Finally, the possibilities of isotope ratio measurements for the discrimination between plant and animal food from conventional and organic production are discussed.
European Food Research and Technology, 1990
Die mittels multidimensionaler Capillargaschromatographie (SE 54/Lipodex B) durchgeführte chirosp... more Die mittels multidimensionaler Capillargaschromatographie (SE 54/Lipodex B) durchgeführte chirospezifische Analyse ergab fürγ-Decalacton mikrobiologischen und pflanzlichen (Ananas, Aprikose, Erdbeere, Guava, Heidelbeere, Mango, gelbe und rote Passionsfrucht, Pfirsich, Pflaume) Ursprungs ee-Werte zwischen 31,6% (R) und 100% (R). Die mit der on-line Capillargaschromatographie — Isotopenverhältnis — Massenspektrometrie (HRGC-IRMS) bestimmtenδ(13C)-Werte (PDB) lagen bei Syntheseprodukten bei −24,4‰, −26,0‰ und −26,9‰ (jeweils±0,5‰), für zwei Handelsproben mikrobiologischen Ursprungs bei −30,3‰ und −31,2‰ (jeweils±0,5‰) sowie fürγ-Decalacton aus Erdbeeren und Pfirsichen unterschiedlicher Varietäten und Herkünfte zwischen −28,2‰ bis −30,5‰ (Mittelwert: −29,2‰) und −38,5‰ bis −40,9‰ (Mittelwert: −39,7‰). Chirality evalution ofγ-decalactone carried out by multidimensional capillary gas chromatography (SE 54/Lipodex B) revealed enantiomeric excess values from 31.6% (R) to 100% (R) for the substance originating from natural sources, including microorganisms and fruits, such as apricot, blueberry, guava, mango, yellow and red passion fruit, pineapple, peach, plum and strawberry. Theδ(13C) values (PDB) determined by on-line capillary gas chromatography-isotope ratio mass spectrometry (HRGC-IRMS) were found to be −24.4‰, −26.0‰ and −26.9‰ (each±0.5‰) for synthetic products, −30.3‰ and −31.2‰(each±0.5‰) for two commercial samples of microbial origin as well as from −28.2‰ to −30.5‰ (mean value: −29.2‰) and from −38.5‰ to −40.9‰ (mean value: −39.7‰) forγ-decalactone from strawberry and peach from various cultivars and origins.
Journal of Chromatography A, 1989
The enantiomeric purity of ibuprofen was determined in a simple manner by diffuse reflectance inf... more The enantiomeric purity of ibuprofen was determined in a simple manner by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy with artificial neural networks (ANNs) methodology. A series of 17 binary mixtures was created using different proportions of the two enantiomeric forms. Sample mixtures were dispersed as a 5% (w/w) mix in KBr, and spectra were measured immediately after mixing.
European Food Research and Technology, 1990
Die mittels multidimensionaler Capillargaschromatographie (SE 54/Lipodex B) durchgeführte chirosp... more Die mittels multidimensionaler Capillargaschromatographie (SE 54/Lipodex B) durchgeführte chirospezifische Analyse ergab fürγ-Decalacton mikrobiologischen und pflanzlichen (Ananas, Aprikose, Erdbeere, Guava, Heidelbeere, Mango, gelbe und rote Passionsfrucht, Pfirsich, Pflaume) Ursprungs ee-Werte zwischen 31,6% (R) und 100% (R). Die mit der on-line Capillargaschromatographie — Isotopenverhältnis — Massenspektrometrie (HRGC-IRMS) bestimmtenδ(13C)-Werte (PDB) lagen bei Syntheseprodukten bei −24,4‰, −26,0‰ und −26,9‰ (jeweils±0,5‰), für zwei Handelsproben mikrobiologischen Ursprungs bei −30,3‰ und −31,2‰ (jeweils±0,5‰) sowie fürγ-Decalacton aus Erdbeeren und Pfirsichen unterschiedlicher Varietäten und Herkünfte zwischen −28,2‰ bis −30,5‰ (Mittelwert: −29,2‰) und −38,5‰ bis −40,9‰ (Mittelwert: −39,7‰). Chirality evalution ofγ-decalactone carried out by multidimensional capillary gas chromatography (SE 54/Lipodex B) revealed enantiomeric excess values from 31.6% (R) to 100% (R) for the substance originating from natural sources, including microorganisms and fruits, such as apricot, blueberry, guava, mango, yellow and red passion fruit, pineapple, peach, plum and strawberry. Theδ(13C) values (PDB) determined by on-line capillary gas chromatography-isotope ratio mass spectrometry (HRGC-IRMS) were found to be −24.4‰, −26.0‰ and −26.9‰ (each±0.5‰) for synthetic products, −30.3‰ and −31.2‰(each±0.5‰) for two commercial samples of microbial origin as well as from −28.2‰ to −30.5‰ (mean value: −29.2‰) and from −38.5‰ to −40.9‰ (mean value: −39.7‰) forγ-decalactone from strawberry and peach from various cultivars and origins.
European Food Research and Technology, 2003
Gas chromatographic (GC) determination of volatile constituents and isotope ratio mass spectromet... more Gas chromatographic (GC) determination of volatile constituents and isotope ratio mass spectrometry (IRMS) analysis of 13C/12C isotope ratios as well as SNIF-NMR analysis of (D/H)-ratios of ethanol in authentic (n=12) and commercial tequila samples (n=13) were used to differentiate analytically between tequila derived from 100% agave (Agave tequilana Weber var. Azul) and tequila produced with other fermentable sugars ('mixed' tequila). Evaluating the correlation of methanol and 2-/3-methyl-1-butanol concentrations, GC analysis was found to be a suitable method for the authenticity assessment of '100% agave' and 'mixed' tequilas. Additional determinations of δ13CVPDB and (D/H) ratios of ethanol were used to show the perspectives and limits of the methods.
European Food Research and Technology, 1997
Gas chromatography and the determination of natural isotope ratios are powerful analytical metho... more Gas chromatography and the determination of natural isotope ratios are powerful analytical methods which can be used to check the authenticity of alcoholic beverages and to detect any adulteration. To check the origin and the authenticity of commercial fruit spirits, whiskies, etc., 197 samples were analysed by gas chromatography, 2H-NMR and 13C isotope mass spectrometry. The discrimination between different varieties was demonstrated by bivariate and multivariate discriminant analysis using different concentrations of volatile compounds such as methanol, butan-1-ol, 2- and 3-methyl-butanol, benzaldehyde and hexanol as well as isotopic data like (D/H)I, (D/H)II and 13C/12C isotopomers of ethanol. The results show that by using multivariate discriminant analysis it is possible to distinguish not only between different groups of spirits, e.g. those made of stone-fruit, malaceous fruit, grain and corn, but also between individual varieties, such as cherry, plum, mirabelle and apple. If the detection of highly rectified ethyl alcohol of agricultural origin and the identification of its raw materials are required, then natural isotope ratios are the only discriminant analytical parameters available.
Wine authentication is the analytical process by which a wine is verified as in compliance with i... more Wine authentication is the analytical process by which a wine is verified as in compliance with its label description (category of quality, geographical origin, year of vintage, grape cultivar). The detection of adulterations or declarations which do not correspond to the labelling are official tasks of wine control and consumer protection. During the last years analytical methods have been improved in this field. Some of them, stable isotope ratio analysis (SIRA) by 2 H-site-specific nuclear magnetic resonance( 2 H-SNIF 1 -NMR), 13 C-, and 18 O-isotope ratio mass spectrometry (IRMS), have been adopted as official methods by the Commission of the European Communities (EC). These methods play a key role in detecting adulterations like addition of water and inadmissible sweetening or chaptalization with beet or cane sugar. In the first part of this paper, fundamental principles of SIRA, interpretation of stable isotope data, and the management of the analytical wine data bank of the European Union (EU) are summarized. By the example of data of vintages from 1992 to 2001 of authentic wines from the German wine-growing regions Franconia and Bavarian part of Lake Constance, influences of geographical origin, year of vintage, grape cultivar, and special meteorological conditions are presented. Precipitation during different periods prior to vintage mainly affects the enrichment or depletion of 2 H, 13 C, and 18 O in wine ethanol and water. The prerequisites, possibilities and limitations for a significant proof of a chaptalization by use of the EU wine data bank in combination with suitable statistical tests (significance level of the Students t-distribution) are discussed by a selected example.
Analytica Chimica Acta, 2002
2-Aminoacetophenone (AAP) is known as the character impact compound responsible for the so called... more 2-Aminoacetophenone (AAP) is known as the character impact compound responsible for the so called untypical 'aging off-flavor' (UTA) in Vitis vinifera wines. The formation of AAP is caused by an oxidative degradation of the phytohormone indole-3-acetic acid (IAA), triggered by sulfuration after fermentation. Using different radical generating systems (hydroxyl and/or superoxide radical generating systems) it could be shown especially that superoxide radicals are responsible for the formation of AAP. Hereby, a pyrrole ring cleavage of IAA yields 3-(2-formylaminophenyl)-3-oxo-propionic acid (FAPOP), N-formyl-2-aminoacetophenone (FAP), and AAP. Analysis of 32 grape musts and their corresponding wines revealed that wines with a higher superoxide radical scavenger activity are less prone to UTA formation. However, UTA is not correlated with the IAA content of the must or wine. Differences in the release of IAA during fermentation of musts derived from early and late harvested grapes indicate a correlation between the ripeness of the processed grapes, the IAA content at the time of sulfuration, and the UTA formation.
Chemie in Unserer Zeit, 2005
Die Isotopenverhältnisse von Wasser, organischem Material und Spurenelementen aus Lebensmitteln h... more Die Isotopenverhältnisse von Wasser, organischem Material und Spurenelementen aus Lebensmitteln hängen von den Umständen und Orten ihrer Entstehung und Verarbeitung ab. Zu Ihrer quantitativen Analyse stehen die Methoden der massenspektrometrischen Isotopenverhältnisanalyse und der positionellen 2H-Analyse zur Verfügung. In deren Anwendung auf die Untersuchung der Herkunft und der Authentizität von Lebensmitteln werden Beispiele für den Nachweis der Wässerung bzw. der Zuckerung von Wein und Obstsäften beschrieben und die Methoden zur Erkennung eines nicht deklarierten Zusatzes von L-Äpfelsäure und Ascorbinsäure erläutert. Die Multielementisotopenanalyse ermöglicht die Erkennung der Herkunft tierischer Produkte (Eier, Milchprodukte, Fleisch) und die Unterscheidung zwischen natürlichen und naturidentischen Aromastoffen. Schließlich werden die Möglichkeiten der Isotopenverhältnisanalyse zur Unterscheidung von pflanzlichen und tierischen Produkten, die nach konventionellen oder ökologischen Verfahren erzeugt wurden, diskutiert.The correlations between isotope ratios in water, organic mass, and trace elements of food and beverages, and the circumstances and sites of their origin and production are outlined, and the methods of mass spectrometric isotope ratio determination and the positional 2H analysis by quantitative NMR measurement are explained. In context with the application of these methods for origin and authenticity investigations of food, examples are given for the proof of watering or sugar addition to wine and fruit juices and methods for the identification of nondeclared additions of L-malic and Lascorbic acids are described. The possibilities of multielement isotope ratio analysis for the identification of origin of animal products (eggs, milk products, meat) and methods for the discriminations between natural and nature identical aroma compounds are outlined. Finally, the possibilities of isotope ratio measurements for the discrimination between plant and animal food from conventional and organic production are discussed.
European Food Research and Technology, 1990
Die mittels multidimensionaler Capillargaschromatographie (SE 54/Lipodex B) durchgeführte chirosp... more Die mittels multidimensionaler Capillargaschromatographie (SE 54/Lipodex B) durchgeführte chirospezifische Analyse ergab fürγ-Decalacton mikrobiologischen und pflanzlichen (Ananas, Aprikose, Erdbeere, Guava, Heidelbeere, Mango, gelbe und rote Passionsfrucht, Pfirsich, Pflaume) Ursprungs ee-Werte zwischen 31,6% (R) und 100% (R). Die mit der on-line Capillargaschromatographie — Isotopenverhältnis — Massenspektrometrie (HRGC-IRMS) bestimmtenδ(13C)-Werte (PDB) lagen bei Syntheseprodukten bei −24,4‰, −26,0‰ und −26,9‰ (jeweils±0,5‰), für zwei Handelsproben mikrobiologischen Ursprungs bei −30,3‰ und −31,2‰ (jeweils±0,5‰) sowie fürγ-Decalacton aus Erdbeeren und Pfirsichen unterschiedlicher Varietäten und Herkünfte zwischen −28,2‰ bis −30,5‰ (Mittelwert: −29,2‰) und −38,5‰ bis −40,9‰ (Mittelwert: −39,7‰). Chirality evalution ofγ-decalactone carried out by multidimensional capillary gas chromatography (SE 54/Lipodex B) revealed enantiomeric excess values from 31.6% (R) to 100% (R) for the substance originating from natural sources, including microorganisms and fruits, such as apricot, blueberry, guava, mango, yellow and red passion fruit, pineapple, peach, plum and strawberry. Theδ(13C) values (PDB) determined by on-line capillary gas chromatography-isotope ratio mass spectrometry (HRGC-IRMS) were found to be −24.4‰, −26.0‰ and −26.9‰ (each±0.5‰) for synthetic products, −30.3‰ and −31.2‰(each±0.5‰) for two commercial samples of microbial origin as well as from −28.2‰ to −30.5‰ (mean value: −29.2‰) and from −38.5‰ to −40.9‰ (mean value: −39.7‰) forγ-decalactone from strawberry and peach from various cultivars and origins.
Journal of Chromatography A, 1989
The enantiomeric purity of ibuprofen was determined in a simple manner by diffuse reflectance inf... more The enantiomeric purity of ibuprofen was determined in a simple manner by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy with artificial neural networks (ANNs) methodology. A series of 17 binary mixtures was created using different proportions of the two enantiomeric forms. Sample mixtures were dispersed as a 5% (w/w) mix in KBr, and spectra were measured immediately after mixing.
European Food Research and Technology, 1990
Die mittels multidimensionaler Capillargaschromatographie (SE 54/Lipodex B) durchgeführte chirosp... more Die mittels multidimensionaler Capillargaschromatographie (SE 54/Lipodex B) durchgeführte chirospezifische Analyse ergab fürγ-Decalacton mikrobiologischen und pflanzlichen (Ananas, Aprikose, Erdbeere, Guava, Heidelbeere, Mango, gelbe und rote Passionsfrucht, Pfirsich, Pflaume) Ursprungs ee-Werte zwischen 31,6% (R) und 100% (R). Die mit der on-line Capillargaschromatographie — Isotopenverhältnis — Massenspektrometrie (HRGC-IRMS) bestimmtenδ(13C)-Werte (PDB) lagen bei Syntheseprodukten bei −24,4‰, −26,0‰ und −26,9‰ (jeweils±0,5‰), für zwei Handelsproben mikrobiologischen Ursprungs bei −30,3‰ und −31,2‰ (jeweils±0,5‰) sowie fürγ-Decalacton aus Erdbeeren und Pfirsichen unterschiedlicher Varietäten und Herkünfte zwischen −28,2‰ bis −30,5‰ (Mittelwert: −29,2‰) und −38,5‰ bis −40,9‰ (Mittelwert: −39,7‰). Chirality evalution ofγ-decalactone carried out by multidimensional capillary gas chromatography (SE 54/Lipodex B) revealed enantiomeric excess values from 31.6% (R) to 100% (R) for the substance originating from natural sources, including microorganisms and fruits, such as apricot, blueberry, guava, mango, yellow and red passion fruit, pineapple, peach, plum and strawberry. Theδ(13C) values (PDB) determined by on-line capillary gas chromatography-isotope ratio mass spectrometry (HRGC-IRMS) were found to be −24.4‰, −26.0‰ and −26.9‰ (each±0.5‰) for synthetic products, −30.3‰ and −31.2‰(each±0.5‰) for two commercial samples of microbial origin as well as from −28.2‰ to −30.5‰ (mean value: −29.2‰) and from −38.5‰ to −40.9‰ (mean value: −39.7‰) forγ-decalactone from strawberry and peach from various cultivars and origins.
European Food Research and Technology, 2003
Gas chromatographic (GC) determination of volatile constituents and isotope ratio mass spectromet... more Gas chromatographic (GC) determination of volatile constituents and isotope ratio mass spectrometry (IRMS) analysis of 13C/12C isotope ratios as well as SNIF-NMR analysis of (D/H)-ratios of ethanol in authentic (n=12) and commercial tequila samples (n=13) were used to differentiate analytically between tequila derived from 100% agave (Agave tequilana Weber var. Azul) and tequila produced with other fermentable sugars ('mixed' tequila). Evaluating the correlation of methanol and 2-/3-methyl-1-butanol concentrations, GC analysis was found to be a suitable method for the authenticity assessment of '100% agave' and 'mixed' tequilas. Additional determinations of δ13CVPDB and (D/H) ratios of ethanol were used to show the perspectives and limits of the methods.
European Food Research and Technology, 1997
Gas chromatography and the determination of natural isotope ratios are powerful analytical metho... more Gas chromatography and the determination of natural isotope ratios are powerful analytical methods which can be used to check the authenticity of alcoholic beverages and to detect any adulteration. To check the origin and the authenticity of commercial fruit spirits, whiskies, etc., 197 samples were analysed by gas chromatography, 2H-NMR and 13C isotope mass spectrometry. The discrimination between different varieties was demonstrated by bivariate and multivariate discriminant analysis using different concentrations of volatile compounds such as methanol, butan-1-ol, 2- and 3-methyl-butanol, benzaldehyde and hexanol as well as isotopic data like (D/H)I, (D/H)II and 13C/12C isotopomers of ethanol. The results show that by using multivariate discriminant analysis it is possible to distinguish not only between different groups of spirits, e.g. those made of stone-fruit, malaceous fruit, grain and corn, but also between individual varieties, such as cherry, plum, mirabelle and apple. If the detection of highly rectified ethyl alcohol of agricultural origin and the identification of its raw materials are required, then natural isotope ratios are the only discriminant analytical parameters available.
Wine authentication is the analytical process by which a wine is verified as in compliance with i... more Wine authentication is the analytical process by which a wine is verified as in compliance with its label description (category of quality, geographical origin, year of vintage, grape cultivar). The detection of adulterations or declarations which do not correspond to the labelling are official tasks of wine control and consumer protection. During the last years analytical methods have been improved in this field. Some of them, stable isotope ratio analysis (SIRA) by 2 H-site-specific nuclear magnetic resonance( 2 H-SNIF 1 -NMR), 13 C-, and 18 O-isotope ratio mass spectrometry (IRMS), have been adopted as official methods by the Commission of the European Communities (EC). These methods play a key role in detecting adulterations like addition of water and inadmissible sweetening or chaptalization with beet or cane sugar. In the first part of this paper, fundamental principles of SIRA, interpretation of stable isotope data, and the management of the analytical wine data bank of the European Union (EU) are summarized. By the example of data of vintages from 1992 to 2001 of authentic wines from the German wine-growing regions Franconia and Bavarian part of Lake Constance, influences of geographical origin, year of vintage, grape cultivar, and special meteorological conditions are presented. Precipitation during different periods prior to vintage mainly affects the enrichment or depletion of 2 H, 13 C, and 18 O in wine ethanol and water. The prerequisites, possibilities and limitations for a significant proof of a chaptalization by use of the EU wine data bank in combination with suitable statistical tests (significance level of the Students t-distribution) are discussed by a selected example.