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Determination of selected mycotoxins in tea
Pustka, Václav ; Maleček, Miroslav (referee) ; Kuchyňa, Jaroslav (advisor)
This diploma thesis deals with the development and validation of an analytical method using high performance liquid chromatography method with fluorescence detection for the simultaneous determination of aflatoxins and ochratoxin A in herbal and fruit tea. The theoretical part describes the most common groups of mycotoxins and the most important methods for their determination in food. The great attention is devoted to HPLC method and the overview of the derivatization techniques for aflatoxins B1 and G1 fluorescence response enhancement. The practical part of this study focuses on the optimization of sample extraction and purification, the settings of the instrumental analysis and the photochemical reactor assembly. The thesis also involves the determination of the basic performance characteristics for the successful method validation.
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Monitoring of the occurrence of mycotoxins in beers from market retail
Wawroszová, Simona ; Pospíchalová, Markéta (referee) ; Běláková, Sylvie (advisor)
This master thesis deals with monitoring of a content of deoxynivalenol, its metabolite deoxynivalenol-3-b-D-glucopyranoside and ochratoxin A in beer samples collected from retail market in the Czech Republic, Poland and Slovakia. The theoretical part describes general characteristics of mycotoxins, its transfer from field barely through malt to beer and its occurrence in beers. Malting process and brewing technology were also mentioned. Subsequently possibilities for a determination of the mycotoxins by the chromatografic and immunochemical method were presented. The experimental section describes analysis of 30 samples of beer. The analyses were conducted using ultra high-performance liquid chromatography with fluorimetric detection (UPLC/FLR) for ochratoxin A and high-performance liquid chromatography coupled with mass spectrometer (HPLC/MS) for deoxynivalenol and its metabolite. Ochratoxin A was detected in 25 of the 30 samples in concentration range of 0,6 - 82,5 ng·l-1. Deoxynivalenol was found in 24 of the 30 samples with concentration range of 2,29 - 12,57 ug·l-1 and deoxynivalenol-3-b-D-glucopyranoside was occure in 19 of the 30 samples in concentration range of 2,45 - 12,47 ug·l-1. It was also assessed the relationship between beer gushing and presence of mycotoxins in beer. No connection between the parameters has been found. Consequently it is not possible to predict beer gushing from the presence of mycotoxins.
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Analysis of mycotoxins from biological matrices using biomembranes and capillary electrophoresis
Kubová, Natália ; Šesták,, Jozef (referee) ; Duša,, Filip (advisor)
This thesis summarizes knowledge about mycotoxins, with focus to ochratoxin A. It also summarizes its tolerable levels of food intake, detoxification and analytical methods for mycotoxins. The work also includes a chapter describing liposomes that were used for the analysis of ochratoxin A by liposomal electrokinetic capillary electrophoresis (LECK). The practical part includes the analysis of ochratoxin A from Aspergillus ochraceus Wilhelm and Aspergillus melleus Yukawa fungi cultivated on a rye and optimization of the method for analysis of ochratoxin A based on liposomes of different compositions. By capillary zone electrophoresis, ochratoxin A is not sufficiently separated and detected in the extracted mixture; conversely, when liposome solutions are used, different migration behavior can be achieved while stabilizing ochratoxin A in solution due to amphiphilic interactions between mycotoxins and liposomes. Therefore, the LEKC method was used for this work. The most suitable liposome composition has been shown to be molar ratios of 25% cholesterol (membrane stabilization) / 50% 2-oleoyl-1-palmitoyl-sn-glycerol 3-phosphocholine (main zwitterionic lipid) / (25% 1,2-diacyl-sn-glycerol)-3-phospho-L-serine (introduction of negative charge).
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Stability of selected mycotoxins in beer
Štáblová, Taťána ; Benešová, Karolína (referee) ; Běláková, Sylvie (advisor)
Mycotoxins are secondary metabolites of moulds, which attack cereals, for example barley, from which mycotoxins then get to beer. This submitted work is focused on ochratoxin A, deoxynivalenol and zearalenone, which can occur in beer. The first part of this master’s thesis consists of literary research, which describes mycotoxins in general, points out their occurrence, prevention of their formation and delivers information about their physical and chemical properties and toxicity. Furthermore, the research contains basis of malt and beer technology, the occurrence of mycotoxins in beer and raw materials for its production. The research describes changes in concentration of mycotoxins across malt and beer production. The next part deals with possibilities of determination of mycotoxins in barley, malt and beer, compares individual methods of their determination and points out many difficulties of some analyses. The experimental part of this work pursues determination of ochratoxin A, deoxynivalenol and zearalenone in different types of beer with the help of UPLC-FLR, HPLC-MS and ELISA. Instrumental techniques are validated and gathered results are compared with the results in literature. The goal of this master’s thesis is to assess the stability of ochratoxin A and deoxynivalenol in beer over time. The gained results show that there are changes in the concentration of ochratoxin A over time, nevertheless those changes show no pattern. Overall, there was a decrease in concentration in 47 % of the samples and an increase in 28 % of them. In the rest of the samples the concentration did not change. The concentration of deoxynivalenol does not change over time. One of the other goals of this thesis is monitoring of selected mycotoxins in beer. The average concentration of ochratoxin A in the samples was 39 ng/l and deoxynivalenol 9,9 g/l. Zearalenone did not occur in any of the samples when determined by liquid chromatography. All results agree with literature. Next, the thesis compares different analytical methods for determination of ochratoxin A, deoxynivalenol and zearalenone. The screening method ELISA is compared to UPLC-FLR and HPLC-MS. The determination of ochratoxin A by ELISA has shown to be time consuming, nevertheless the results responded to instrumental technique. ELISA overestimated the results of determination of deoxynivalenol in beer by 363–697 % and with zearalenone there were found false positive results.
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Determination of selected mycotoxins in tea
Pustka, Václav ; Maleček, Miroslav (referee) ; Kuchyňa, Jaroslav (advisor)
This diploma thesis deals with the development and validation of an analytical method using high performance liquid chromatography method with fluorescence detection for the simultaneous determination of aflatoxins and ochratoxin A in herbal and fruit tea. The theoretical part describes the most common groups of mycotoxins and the most important methods for their determination in food. The great attention is devoted to HPLC method and the overview of the derivatization techniques for aflatoxins B1 and G1 fluorescence response enhancement. The practical part of this study focuses on the optimization of sample extraction and purification, the settings of the instrumental analysis and the photochemical reactor assembly. The thesis also involves the determination of the basic performance characteristics for the successful method validation.
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Stability of selected mycotoxins in beer
Štáblová, Taťána ; Benešová, Karolína (referee) ; Běláková, Sylvie (advisor)
Mycotoxins are secondary metabolites of moulds, which attack cereals, for example barley, from which mycotoxins then get to beer. This submitted work is focused on ochratoxin A, deoxynivalenol and zearalenone, which can occur in beer. The first part of this master’s thesis consists of literary research, which describes mycotoxins in general, points out their occurrence, prevention of their formation and delivers information about their physical and chemical properties and toxicity. Furthermore, the research contains basis of malt and beer technology, the occurrence of mycotoxins in beer and raw materials for its production. The research describes changes in concentration of mycotoxins across malt and beer production. The next part deals with possibilities of determination of mycotoxins in barley, malt and beer, compares individual methods of their determination and points out many difficulties of some analyses. The experimental part of this work pursues determination of ochratoxin A, deoxynivalenol and zearalenone in different types of beer with the help of UPLC-FLR, HPLC-MS and ELISA. Instrumental techniques are validated and gathered results are compared with the results in literature. The goal of this master’s thesis is to assess the stability of ochratoxin A and deoxynivalenol in beer over time. The gained results show that there are changes in the concentration of ochratoxin A over time, nevertheless those changes show no pattern. Overall, there was a decrease in concentration in 47 % of the samples and an increase in 28 % of them. In the rest of the samples the concentration did not change. The concentration of deoxynivalenol does not change over time. One of the other goals of this thesis is monitoring of selected mycotoxins in beer. The average concentration of ochratoxin A in the samples was 39 ng/l and deoxynivalenol 9,9 g/l. Zearalenone did not occur in any of the samples when determined by liquid chromatography. All results agree with literature. Next, the thesis compares different analytical methods for determination of ochratoxin A, deoxynivalenol and zearalenone. The screening method ELISA is compared to UPLC-FLR and HPLC-MS. The determination of ochratoxin A by ELISA has shown to be time consuming, nevertheless the results responded to instrumental technique. ELISA overestimated the results of determination of deoxynivalenol in beer by 363–697 % and with zearalenone there were found false positive results.
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Analysis of mycotoxins from biological matrices using biomembranes and capillary electrophoresis
Kubová, Natália ; Šesták,, Jozef (referee) ; Duša,, Filip (advisor)
This thesis summarizes knowledge about mycotoxins, with focus to ochratoxin A. It also summarizes its tolerable levels of food intake, detoxification and analytical methods for mycotoxins. The work also includes a chapter describing liposomes that were used for the analysis of ochratoxin A by liposomal electrokinetic capillary electrophoresis (LECK). The practical part includes the analysis of ochratoxin A from Aspergillus ochraceus Wilhelm and Aspergillus melleus Yukawa fungi cultivated on a rye and optimization of the method for analysis of ochratoxin A based on liposomes of different compositions. By capillary zone electrophoresis, ochratoxin A is not sufficiently separated and detected in the extracted mixture; conversely, when liposome solutions are used, different migration behavior can be achieved while stabilizing ochratoxin A in solution due to amphiphilic interactions between mycotoxins and liposomes. Therefore, the LEKC method was used for this work. The most suitable liposome composition has been shown to be molar ratios of 25% cholesterol (membrane stabilization) / 50% 2-oleoyl-1-palmitoyl-sn-glycerol 3-phosphocholine (main zwitterionic lipid) / (25% 1,2-diacyl-sn-glycerol)-3-phospho-L-serine (introduction of negative charge).
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Monitoring of the occurrence of mycotoxins in beers from market retail
Wawroszová, Simona ; Pospíchalová, Markéta (referee) ; Běláková, Sylvie (advisor)
This master thesis deals with monitoring of a content of deoxynivalenol, its metabolite deoxynivalenol-3-b-D-glucopyranoside and ochratoxin A in beer samples collected from retail market in the Czech Republic, Poland and Slovakia. The theoretical part describes general characteristics of mycotoxins, its transfer from field barely through malt to beer and its occurrence in beers. Malting process and brewing technology were also mentioned. Subsequently possibilities for a determination of the mycotoxins by the chromatografic and immunochemical method were presented. The experimental section describes analysis of 30 samples of beer. The analyses were conducted using ultra high-performance liquid chromatography with fluorimetric detection (UPLC/FLR) for ochratoxin A and high-performance liquid chromatography coupled with mass spectrometer (HPLC/MS) for deoxynivalenol and its metabolite. Ochratoxin A was detected in 25 of the 30 samples in concentration range of 0,6 - 82,5 ng·l-1. Deoxynivalenol was found in 24 of the 30 samples with concentration range of 2,29 - 12,57 ug·l-1 and deoxynivalenol-3-b-D-glucopyranoside was occure in 19 of the 30 samples in concentration range of 2,45 - 12,47 ug·l-1. It was also assessed the relationship between beer gushing and presence of mycotoxins in beer. No connection between the parameters has been found. Consequently it is not possible to predict beer gushing from the presence of mycotoxins.
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Rizika plísní a mykotoxinů v chovu zvířat
BOHÁČKOVÁ, Lenka
The aim of this work is to provide information about what toxigenic fungi and mycotoxins are. The mycotoxins were highlighted the most important types of them, the characteristics, biological effects, methods of determining. Aflatoxins are naturally commonly occurring mycotoxins, which are produced by toxigenic filamentous fungi of the genus Aspergillus. These are substances with a very high toxicity. In conclusion, there are described the methods of detection, prevention and decontamination of mycotoxins. The decontamination is carried out by physical, chemical or biological methods.
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