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- Alternaria (3)
- Crystal structure (3)
- Alternariol (2)
- Deacetyl tenuazonic acid (2)
- Degradation (2)
- Hydrazone (2)
- Tenuazonic acid (2)
- X-ray single crystal diffraction (2)
- Zearalenone (2)
- 2,4-Dinitrophenylhydrazine (1)
Mycotoxins are toxic secondary metabolites of ubiquitously occurring moulds. Through the consumption of contaminated foods, they can cause acute or chronic intoxications in humans. Here, it is demonstrated how covalent hydrazine chemistry can be used to improve the performance of instrumental methods for the quantification of trace level food mycotoxins. In the case of the Alternaria mycotoxin tenuazonic acid, pre-column derivatisation with 2,4-dinitrophenylhydrazine resolved chromatographic issues due to the chemical properties of the analyte and allowed for its rapid, sensitive and selective quantification in cereals and beer by high performance liquid chromatography- ion-trap two stage mass spectrometry (HPLC-IT-MS2). Tenuazonic acid could be detected for the first time in beer and buckwheat flour. Although the encountered levels were too low to cause acute intoxications, the frequency of contamination indicated possible health risks due to chronic exposure. In a second scenario, dynamic covalent hydrazine chemistry (DCHC) was exploited for a novel extraction and cleanup method applicable to the Fusarium mycotoxin zearalenone occurring in edible oils. Zearalenone was extracted by hydrazone formation on a hydrazinefunctionalised polymer resin and subsequently released hydrolytically for quantification by HPLC-fluorescence detection (HPLC- FLD). The high selectivity of the approach allowed for the omission of MS detection and immunoaffinity cleanup. The DCHC method was superior to previously published methods in terms of handling efforts, cost, precision and selectivity and is well suited for the monitoring of the current European maximum level for zearalenone in refined maize oil. In the second part of the dissertation, possible degradation routes of Alternaria mycotoxins upon storage and bread baking are discussed. In the frame of a kinetic study, it was shown that tenuazonic acid is degraded by two parallel processes, deacetylation and epimerisation, when stored in aqueous solution (half-life at 25 °C ~ 74 days). The primary degradation product deacetyl tenuazonic acid was less stable than its parent compound and degraded rapidly in beverage matrices. In model baking experiments it was furthermore revealed that alternariol, alternariol monomethyl ether and altenuene are stable under typical baking conditions. A newly identified degradation route, which is based on a sequence of hydrolysis and decarboxylation, caused only minor substance losses (< 1 %). Still, the degradation products could be detected in commercial rusk and crispbread by HPLC-tandem mass spectrometry (HPLC-MS/MS).
Deacetyl tenuazonic acid
(2009)
The stability of the Alternaria mycotoxins alternariol, alternariol monomethyl ether, and altenuene upon bread baking was investigated by model experiments using a spiked wholemeal wheat flour matrix. For alternariol and alternariol monomethyl ether, but not for altenuene, degradation products, formed through a sequence of hydrolysis and decarboxylation, could be identified in pilot studies. The simultaneous quantification of alternariol, alternariol monomethyl ether, altenuene, and the degradation products was achieved by a newly developed high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) multimethod. The obtained quantitative data indicate that the Alternaria mycotoxins are barely degraded during wet baking, while significant degradation occurs upon dry baking, with the stability decreasing in the order alternariol monomethyl ether > alternariol > altenuene. The novel degradation products could be detected after the wet baking of flour spiked with alternariol and in a sample survey of 24 commercial cereal based baking products.
Certified reference materials (CRMs) are a versatile tool for quality assurance in the chemical laboratory. In the case of acrylamide analysis, the availability of appropriate materials was rather limited. This lack of acrylamide matrix CRMs has now been overcome by the development of two European reference materials (ERM) for the determination of acrylamide in food (crispbread, ERM-BD272, and rusk, ERM-BD274). This article describes the preparation of the materials, provides the results of the homogeneity and stability studies, and presents and discusses the outcome of the certification studies. Expert laboratories from different European countries took part in the certification studies using various analytical methods. The acrylamide mass fractions were certified to 980 µg kg-1 for crispbread and 74 µg kg-1 for rusk.
Mycotoxins are natural contaminants produced by a range of fungal species. Their common occurrence in food and feed poses a threat to the health of humans and animals. This threat is caused either by the direct contamination of agricultural commodities or by a "carry-over" of mycotoxins and their metabolites into animal tissues, milk, and eggs after feeding of contaminated hay or corn. As a consequence of their diverse chemical structures and varying physical properties, mycotoxins exhibit a wide range of biological effects. Individual mycotoxins can be genotoxic, mutagenic, carcinogenic, teratogenic, and oestrogenic. To protect consumer health and to reduce economic losses, surveillance and control of mycotoxins in food and feed has become a major objective for producers, regulatory authorities and researchers worldwide. However, the variety of chemical structures makes it impossible to use one single technique for mycotoxin analysis. Hence, a vast number of analytical methods has been developed and validated. The heterogeneity of food matrices combined with the demand for a fast, simultaneous and accurate determination of multiple mycotoxins creates enormous challenges for routine analysis. The most crucial issues will be discussed in this review. These are (1) the collection of representative samples, (2) the performance of classical and emerging analytical methods based on chromatographic or immunochemical techniques, (3) the validation of official methods for enforcement, and (4) the limitations and future prospects of the current methods.
Sulfur dioxide (SO2) or sulfites are the most common preservatives used in winemaking. The level of total SO2 is subject to regulation. Currently, the regulatory determination of total SO2 (including sulfites) is done by the optimized Monier–Williams (OMW) method, which includes time-consuming distillation and titration steps. This paper describes the development and application of an alternative, rapid, straightforward, and reliable method for the determination of total sulfite in wine. In this method, a simple oxidation step using alkaline hydrogen peroxide (H2O2) solution is followed by ion chromatographic (IC) analysis of sulfate coupled with conductometric detection. Thirteen wines were analyzed in order to compare the in-sample oxidation method with the OMW-procedure. A t-test revealed satisfying compliance regarding sample preparation, i.e., alkaline H2O2 treatment and acidic distillation (OMW method). Comparable results were also obtained between IC analysis and acid/base titration. Our results indicate that the novel method (limit of quantification: 4 mg SO2 L-1) is well suited for the cost-efficient monitoring of regulatory limits.
Alternariol
(2010)
In the title compound (systematic name: 3,7,9-trihydroxy-1-methyl-6H-benzo[c]chromen-6-one), C14H10O5, the methyl group is shifted out of the molecular plane due to a steric collision, thus causing a slight twist of the benzene rings. The molecular structure is stabilized by an intramolecular O-H...O hydrogen bond, generating an S(6) ring. In the crystal, molecules are connected by intermolecular O-H...O hydrogen bonds into a three-dimensional network.
Tenuazonic acid (TA) is a major water soluble Alternaria mycotoxin. In the present work, a method for the quantification of TA in beer by liquid chromatography-ion-trap multistage mass spectrometry after derivatization with 2,4-dinitrophenylhydrazine is described. The method is based on a rapid workup procedure and features a LOD of 2 µg/kg without preconcentration using 400 mg of sample. Validation was performed for a working range of 8-500 µg/kg.
A total of 43 beers of different brewing styles (pilsener, wheat beer, bock beer, dark beer and alcohol free beer) was analysed. TA was detected in 37 samples, 16 samples were above the LOQ. An average content of 11 µg/kg was found, the highest incidence being 175 ± 13 µg/kg. To our knowledge, this is the first report on the occurrence of TA in beer and beverages in general.