European Food Research and Technology, Nov 20, 2021
Craft breweries that tend to convince consumers with new interpretations of (ancient) beer styles... more Craft breweries that tend to convince consumers with new interpretations of (ancient) beer styles increasingly influence the traditional beer market. Thereby, also ingredients not directly compliant with German beer purity laws come into use. Official food control currently faces the general problem of verifying food authenticity based on instrumental analytical methods. Related tasks in this field are the detection of non-labelled ingredients and the verification of product claims such as special food processing methods. For that purpose, chemometric analysis of high-resolution 1H NMR spectra was applied for the differentiation of related beer styles including also special beers. It could be shown that pilsner style beers, wheat beers, India pale ales, sour beers, and special beers can be easily differentiated applying consecutive principal component analysis. Thereby, it turned out that crafted pilsner style beers are distinguishable from industrial pilsner style beers based on their organic acid profiles. Furthermore, three conspicuous compounds present in two different batches of only one of the beer samples were identified as allyl alcohol, 1,3-propanediol, and 3-hydroxypropionic acid directly from the NMR spectra without any further analytical efforts. Finally, the present paper serves as a proof of concept that NMR-based quantification is also possible using chemical shift information instead of signal intensities/integrals—at least in special cases.
European Food Research and Technology, Jun 28, 2023
1 H NMR spectroscopy was applied to analyse samples of "Swabian-Hall Quality Pork" with protected... more 1 H NMR spectroscopy was applied to analyse samples of "Swabian-Hall Quality Pork" with protected geographical indication (PGI). To obtain maximum chemical information sample preparation was based on both polar extraction and non-polar extraction. A non-targeted approach was used to analyse the 1 H NMR data followed by principal component analysis (PCA), linear discriminant analysis (LDA), and cross-validation (CV) embedded in a Monte Carlo (MC) resampling approach. A total of 275 raw pork samples were collected in the years 2018 to 2021. The correct prediction rate of "Swabian-Hall Quality Pork" was about 92% on average for both models based on either the polar or non-polar metabolites. In addition, 1 H NMR data describing the polar and non-polar metabolites were combined in a classification model to improve the prediction accuracy. By performing a mid-level data fusion, a correct prediction rate of 98% was achieved. Furthermore, spectral regions in the NMR spectra of the polar and non-polar metabolites that are relevant for the classification of the pork samples were identified to describe potential chemical marker compounds.
Meat species of raw meat and processed meat products were investigated by H NMR spectroscopy with... more Meat species of raw meat and processed meat products were investigated by H NMR spectroscopy with subsequent multivariate data analysis. Sample preparation was based on aqueous extraction combined with ultrafiltration in order to reduce macromolecular components in the extracts. H NMR data was analyzed by using a non-targeted approach followed by principal component analysis (PCA), linear discrimination analysis (LDA), and cross-validation (CV) embedded in a Monte Carlo (MC) resampling approach. A total of raw meat samples (pork, beef, poultry, and lamb) and processed meat samples (pork, beef, poultry) were collected between the years and. A % correct prediction rate was achieved if the raw meat samples were classified according to meat species. Predicting processed meat products was slightly less successful (%) with this approach. Furthermore, identification of spectral regions that are relevant for the classification via polar chemical markers was performed. Finally, data on polar metabolites were fused with previously published H NMR data on non-polar metabolites in order to build a broader classification model and to improve prediction accuracy.
Craft breweries that tend to convince consumers with new interpretations of (ancient) beer styles... more Craft breweries that tend to convince consumers with new interpretations of (ancient) beer styles increasingly influence the traditional beer market. Thereby, also ingredients not directly compliant with German beer purity laws come into use. Official food control currently faces the general problem of verifying food authenticity based on instrumental analytical methods. Related tasks in this field are the detection of non-labelled ingredients and the verification of product claims such as special food processing methods. For that purpose, chemometric analysis of high-resolution 1H NMR spectra was applied for the differentiation of related beer styles including also special beers. It could be shown that pilsner style beers, wheat beers, India pale ales, sour beers, and special beers can be easily differentiated applying consecutive principal component analysis. Thereby, it turned out that crafted pilsner style beers are distinguishable from industrial pilsner style beers based on their organic acid profiles. Furthermore, three conspicuous compounds present in two different batches of only one of the beer samples were identified as allyl alcohol, 1,3-propanediol, and 3-hydroxypropionic acid directly from the NMR spectra without any further analytical efforts. Finally, the present paper serves as a proof of concept that NMR-based quantification is also possible using chemical shift information instead of signal intensities/integrals—at least in special cases.
The roasting process is an important step in coffee production, leading to important physical and... more The roasting process is an important step in coffee production, leading to important physical and chemical changes that are responsible for the sensory quality of a coffee beverage. Besides the commonly used drum roasters, a newly developed infrared roaster can be used to roast green coffee beans. In this study, 1H nuclear magnetic resonance (NMR) spectroscopy was used to analyze the fat and aqueous extracts of coffee beans roasted to different degrees of roasting using a professional drum roaster, a hot air fluidized bed sample roaster and an infrared roaster. Caffeine-containing and decaffeinated Coffea arabica coffee samples were used to monitor the roasting process in the different roasters. Compared with the drum-roasted coffee sample, the formation and degradation of NMR-detectable components in the coffee sample roasted with the infrared roaster and the hot air roaster were time-dependent. In the decaffeinated coffee sample, compounds such as kahweol, caffeoylquinic acid and ...
The importance of animal welfare and the organic production of chicken eggs has increased in the ... more 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 develop a non-targeted lipidomic LC-ESI-IM-qToF-MS method based on 270 egg samples, which achieved a classification accuracy of 96.3%. Subsequently, surrogate minimal depth (SMD) was applied to select important variables identified as carotenoids and lipids based on their MS/MS spectra. The LC-MS results were compared with FT-NIR spectroscopy analysis as a low-resolution screening method and achieved 80.0% accuracy. Here, SMD selected parts of the spectrum which are associated with lipids and proteins. Furthermore, we used SMD for low-level data fusion to analyze relations between the variables of the LC-MS and the FT-NIR spectroscopy datasets...
Highly reactive decomposition products of (deuterated) chloroform can deteriorate samples dissolv... more Highly reactive decomposition products of (deuterated) chloroform can deteriorate samples dissolved in this commonly used NMR solvent. For sensitive samples (such as peptides, unsaturated fatty acids, vitamins), this can lead to abnormal NMR spectra (e.g. signal shifts depending on pH, attenuation of signals over time due to chemical changes of analytes, new signals from reaction products). Such irreproducibly influenced spectra are especially problematic for non-targeted analysis methods. To prevent these artefacts, chlorine, phosgene and hydrochloric acid need to be eliminated from deuterated chloroform prior to its use. Since the common stabilization methods have proven insufficient for sensitive NMR samples, another purging method has been tested: Mitigation is easily and reliably achieved by washing the deuterated chloroform with concentrated Na2CO3-solution and subsequent desiccation with oven-dried Na2CO3.
European Food Research and Technology, Nov 20, 2021
Craft breweries that tend to convince consumers with new interpretations of (ancient) beer styles... more Craft breweries that tend to convince consumers with new interpretations of (ancient) beer styles increasingly influence the traditional beer market. Thereby, also ingredients not directly compliant with German beer purity laws come into use. Official food control currently faces the general problem of verifying food authenticity based on instrumental analytical methods. Related tasks in this field are the detection of non-labelled ingredients and the verification of product claims such as special food processing methods. For that purpose, chemometric analysis of high-resolution 1H NMR spectra was applied for the differentiation of related beer styles including also special beers. It could be shown that pilsner style beers, wheat beers, India pale ales, sour beers, and special beers can be easily differentiated applying consecutive principal component analysis. Thereby, it turned out that crafted pilsner style beers are distinguishable from industrial pilsner style beers based on their organic acid profiles. Furthermore, three conspicuous compounds present in two different batches of only one of the beer samples were identified as allyl alcohol, 1,3-propanediol, and 3-hydroxypropionic acid directly from the NMR spectra without any further analytical efforts. Finally, the present paper serves as a proof of concept that NMR-based quantification is also possible using chemical shift information instead of signal intensities/integrals—at least in special cases.
European Food Research and Technology, Jun 28, 2023
1 H NMR spectroscopy was applied to analyse samples of "Swabian-Hall Quality Pork" with protected... more 1 H NMR spectroscopy was applied to analyse samples of "Swabian-Hall Quality Pork" with protected geographical indication (PGI). To obtain maximum chemical information sample preparation was based on both polar extraction and non-polar extraction. A non-targeted approach was used to analyse the 1 H NMR data followed by principal component analysis (PCA), linear discriminant analysis (LDA), and cross-validation (CV) embedded in a Monte Carlo (MC) resampling approach. A total of 275 raw pork samples were collected in the years 2018 to 2021. The correct prediction rate of "Swabian-Hall Quality Pork" was about 92% on average for both models based on either the polar or non-polar metabolites. In addition, 1 H NMR data describing the polar and non-polar metabolites were combined in a classification model to improve the prediction accuracy. By performing a mid-level data fusion, a correct prediction rate of 98% was achieved. Furthermore, spectral regions in the NMR spectra of the polar and non-polar metabolites that are relevant for the classification of the pork samples were identified to describe potential chemical marker compounds.
Meat species of raw meat and processed meat products were investigated by H NMR spectroscopy with... more Meat species of raw meat and processed meat products were investigated by H NMR spectroscopy with subsequent multivariate data analysis. Sample preparation was based on aqueous extraction combined with ultrafiltration in order to reduce macromolecular components in the extracts. H NMR data was analyzed by using a non-targeted approach followed by principal component analysis (PCA), linear discrimination analysis (LDA), and cross-validation (CV) embedded in a Monte Carlo (MC) resampling approach. A total of raw meat samples (pork, beef, poultry, and lamb) and processed meat samples (pork, beef, poultry) were collected between the years and. A % correct prediction rate was achieved if the raw meat samples were classified according to meat species. Predicting processed meat products was slightly less successful (%) with this approach. Furthermore, identification of spectral regions that are relevant for the classification via polar chemical markers was performed. Finally, data on polar metabolites were fused with previously published H NMR data on non-polar metabolites in order to build a broader classification model and to improve prediction accuracy.
Craft breweries that tend to convince consumers with new interpretations of (ancient) beer styles... more Craft breweries that tend to convince consumers with new interpretations of (ancient) beer styles increasingly influence the traditional beer market. Thereby, also ingredients not directly compliant with German beer purity laws come into use. Official food control currently faces the general problem of verifying food authenticity based on instrumental analytical methods. Related tasks in this field are the detection of non-labelled ingredients and the verification of product claims such as special food processing methods. For that purpose, chemometric analysis of high-resolution 1H NMR spectra was applied for the differentiation of related beer styles including also special beers. It could be shown that pilsner style beers, wheat beers, India pale ales, sour beers, and special beers can be easily differentiated applying consecutive principal component analysis. Thereby, it turned out that crafted pilsner style beers are distinguishable from industrial pilsner style beers based on their organic acid profiles. Furthermore, three conspicuous compounds present in two different batches of only one of the beer samples were identified as allyl alcohol, 1,3-propanediol, and 3-hydroxypropionic acid directly from the NMR spectra without any further analytical efforts. Finally, the present paper serves as a proof of concept that NMR-based quantification is also possible using chemical shift information instead of signal intensities/integrals—at least in special cases.
The roasting process is an important step in coffee production, leading to important physical and... more The roasting process is an important step in coffee production, leading to important physical and chemical changes that are responsible for the sensory quality of a coffee beverage. Besides the commonly used drum roasters, a newly developed infrared roaster can be used to roast green coffee beans. In this study, 1H nuclear magnetic resonance (NMR) spectroscopy was used to analyze the fat and aqueous extracts of coffee beans roasted to different degrees of roasting using a professional drum roaster, a hot air fluidized bed sample roaster and an infrared roaster. Caffeine-containing and decaffeinated Coffea arabica coffee samples were used to monitor the roasting process in the different roasters. Compared with the drum-roasted coffee sample, the formation and degradation of NMR-detectable components in the coffee sample roasted with the infrared roaster and the hot air roaster were time-dependent. In the decaffeinated coffee sample, compounds such as kahweol, caffeoylquinic acid and ...
The importance of animal welfare and the organic production of chicken eggs has increased in the ... more 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 develop a non-targeted lipidomic LC-ESI-IM-qToF-MS method based on 270 egg samples, which achieved a classification accuracy of 96.3%. Subsequently, surrogate minimal depth (SMD) was applied to select important variables identified as carotenoids and lipids based on their MS/MS spectra. The LC-MS results were compared with FT-NIR spectroscopy analysis as a low-resolution screening method and achieved 80.0% accuracy. Here, SMD selected parts of the spectrum which are associated with lipids and proteins. Furthermore, we used SMD for low-level data fusion to analyze relations between the variables of the LC-MS and the FT-NIR spectroscopy datasets...
Highly reactive decomposition products of (deuterated) chloroform can deteriorate samples dissolv... more Highly reactive decomposition products of (deuterated) chloroform can deteriorate samples dissolved in this commonly used NMR solvent. For sensitive samples (such as peptides, unsaturated fatty acids, vitamins), this can lead to abnormal NMR spectra (e.g. signal shifts depending on pH, attenuation of signals over time due to chemical changes of analytes, new signals from reaction products). Such irreproducibly influenced spectra are especially problematic for non-targeted analysis methods. To prevent these artefacts, chlorine, phosgene and hydrochloric acid need to be eliminated from deuterated chloroform prior to its use. Since the common stabilization methods have proven insufficient for sensitive NMR samples, another purging method has been tested: Mitigation is easily and reliably achieved by washing the deuterated chloroform with concentrated Na2CO3-solution and subsequent desiccation with oven-dried Na2CO3.
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Papers by Thomas Kuballa