Papers by Vladimír Kocourek
Changes in PAH levels during production of rapeseed oil
Food additives and contaminants, Jul 1, 1998
The influence of technological operations during rapeseed oil production on polycyclic aromatic h... more The influence of technological operations during rapeseed oil production on polycyclic aromatic hydrocarbon (PAH) concentrations in by-products, intermediate and final oils was evaluated. The decrease of light PAHs, benz(a)anthracene and benzo(a)pyrene during processing of crude oil to the deodorized product was significant at the 95% confidence interval in most batches analysed. Deodorization and alkali-refining were the steps contributing most to the PAH decrease. The relationship between PAH levels in rapeseed (and consequently in refined oil) and the duration of storage period was studied. The contamination of raw material processed a short time after harvesting was significantly higher than that of the rapeseed stored in silos for several months. Analyses of rapeseed samples, which were re-purified in the laboratory, revealed that solid particles, which contaminate rapeseed during harvesting, initial treatment, transport and storage, contributed to PAH contamination to the extent of 36% (light PAHs) to 64% (heavy PAHs) on average. Further experiments demonstrated that PAHs in re-purified rapeseed were concentrated in the cuticular layer, because they were removed well from the whole seeds by simple rinsing with organic solvent in an ultrasonic bath without losses of rapeseed oil. Alternative expressions of total PAH contamination (e.g. various PAH groups and/or differently defined B(a)P toxic equivalents) are discussed and their effect on drawing conclusions about PAH elimination rate has been demonstrated.
Journal of Chromatography A, Dec 1, 2002
Analytical method for the determination of ultra-trace levels of nitro-PAHs in various biotic mat... more Analytical method for the determination of ultra-trace levels of nitro-PAHs in various biotic matrices has been developed. Soxhlet extraction and / or solvent extraction enhanced by sonication were used for isolation of target analytes; GPC followed by SPE were employed for purification of crude extracts. GC-MS / NCI technique was utilised for identification / quantitation of target analytes. Performance characteristics of implemented method were obtained through thorough in-house validation procedure. The main sources of uncertainties were critically evaluated, possible strategies of their elimination / minimisation were considered and consequently employed. Examination of real-life samples of various foodstuffs (complete human diet, mate tea, pumpkin seed oil, parsley, sausages) was performed in this study.
Residues of daminozide in apple products
Degradation of thiram, dodin and trifloxystrobin in apples designated for baby food production during 2005 and 2006 growing seasons
Food Chemistry, 2021
This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Czech Journal of Food Sciences, 2019
In 2008, the European Commission highlighted the risk of wine mislabelling regarding the geograph... more In 2008, the European Commission highlighted the risk of wine mislabelling regarding the geographical origin and varietal identification. While analytical methods for the identification of wine by geographical origin exist, a reliable strategy for authentication of wine variety is still missing. Here, we investigate the suitability of the metabolomic fingerprinting of ethyl acetate wine extracts, using ultra-high-performance liquid chromatography coupled to high-resolution tandem mass spectrometry. In total, 43 white wine samples (three varieties) were analysed within our study. The generated data were processed by principal component analysis and then by partial least squares discriminant analysis. The resulting statistical models were validated and assessed according to their R2 (cum) and Q2 (cum) parameters. The most promising models were based on positive ionisation data, enabling successful classification of 92% of wine samples.
Czech Journal of Food Sciences, 2019
The aim of the study was to develop an efficient method for assessment of meat origin and determi... more The aim of the study was to develop an efficient method for assessment of meat origin and determination of net muscle protein (NMP; based on amino acids and β-alanylhistidine dipeptides) in meat products using the ultra-high performance liquid chromatography coupled with mass spectrometry. As an important result, a database of ratios of particular amino acids to 3-metylhistidine, applicable for muscle protein origin confirmation, was established. Based on the specific ratios of 1-methylhisitidine/3-methylhistidine, revealing of undeclared addition of 2% of chicken meat to the pork was enabled. Similar outcome was achieved by considering the ratios of β-alanylhistidine dipeptides. In the case of chicken-pork and pork-beef admixtures, as low additions as 0.5 and 2% of chicken or pork adulterant could be recognized. The ratio of 4-hydroxyproline/3-methylhisitidine was shown to be diagnostic for detection undeclared addition of 0.5 and 1.5% of connective tissues into the pork and chicke...
Journal of Agricultural and Food Chemistry, 2019
Modern pesticides rapidly degrade after their application due to both physicochemical factors and... more Modern pesticides rapidly degrade after their application due to both physicochemical factors and through biotransformation. Consequently, pesticide residues in samples might be either undetectable or detected at low concentrations (≤ 10 µg/kg). Under such conditions, a monitoring of pesticide metabolites in samples might be a conceivable solution enabling the documentation of earlier pesticide use. Analysis of metabolites might pose analytical challenges, because pesticide degradation leads to the production of a number of metabolites, differing somewhat in their structure and polarity. This study was focused on the determination of pesticide residues and their metabolites in samples of grapevine and wine, using ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry, with the objective of supporting the possibility of the verification of the method of farming. It documents the identification of pesticide metabolites commonly used in conventional farming and provides a characterization of pesticide degradation during grapevine growth, maturation and during the wine-making process.
Food Chemistry, 2019
Due to unique phytochemicals contained, Vaccinum berries are known to have a number of positive h... more Due to unique phytochemicals contained, Vaccinum berries are known to have a number of positive health effects. In this context, lingonberries (Vaccinium vitis-idaea) are considered to be the most effective, thus finding many uses. Recently, fraud suspicion on lingonberriesbased products has been reported, partial or even total replacement by less valued cranberries (Vaccinium macrocarpon) was found. In this study, metabolomic fingerprinting employing instrumental platform consisting of U-HPLC-HRMS/MS was investigated for discrimination between the two Vaccinum berries species. Methanolic extracts of 33 authentic samples from two harvest years were analyzed and chemometric evaluation was performed to identify significant marker compounds, their stability during drying process was assessed, too. The characteristic markers most contributing to berries classification were representatives of polyphenols and phospholipids. Peonidin 3-O-arabinoside and myricetin 3-O-glucoside, not occurring in lingonberries, enabled to discover the presence of cranberries in prepared admixtures down to 1 % (w/w).
Food Control, 2017
Rapid approach for the determination of alcoholic strength and overall quality check of various s... more Rapid approach for the determination of alcoholic strength and overall quality check of various spirit drinks and wines using GC-MS, (2017),
Validation of insecticide aerosol generated by smoke-generator for German cockroach control
The aim of this article is to give preliminary report on efficacy of smoke-generator Vulcan SG (f... more The aim of this article is to give preliminary report on efficacy of smoke-generator Vulcan SG (former Ultimate super SG), containing pirimiphos-methyl and cypermethrin, against German cockroaches. The small scale experiments simulated semi-field conditions: cockroaches were exposed to smoke from pyrotechnic generators in plastic cubicles incorporated in experimental outdoor room-units. The airborne concentration of active ingredients - estimated by gas chromatography method – decreased significantly within 6-12 hours after preparation release. We found that the efficacy of the smoke-aerosol reached 100% cockroach mortality during the first 3 hours of exposure. During the consequent 6-12hours of exposure the cockroach tremor (knock-down) was high while mortality was low, when estimated 24 hour after exposure interruption.
Talanta, 2013
Ambient mass spectrometry employing a direct analysis in real time (DART) ion source coupled to a... more Ambient mass spectrometry employing a direct analysis in real time (DART) ion source coupled to a medium high-resolution/accurate mass time-of-flight mass spectrometer (TOFMS) was used as a rapid tool for metabolomic fingerprinting to study the effects of supplemental feeding with cereals (triticale) on the composition of muscle metabolites of common carp (Cyprinus carpio L.). First, the sample extraction and DART-TOFMS instrumental conditions were optimized to obtain the broadest possible representation of ionizable compounds occurring in the extracts obtained from common carp muscle. To this end, a simultaneous (all-in-one) extraction procedure was developed employing water and cyclohexane mixture as the extraction solvents. Under these conditions both polar as well as non-polar metabolites were isolated within a single extraction step. Next, the metabolomic fingerprints (mass spectra) of a large set of common carp muscle extracts were acquired. Finally, the experimental data were statistically evaluated using principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA). Using this approach, differentiation of common carp muscle in response to dietary supplementation (feeding with and without cereals) was feasible. Correct classification was obtained based on the assessment of polar and as well as non-polar extracts fingerprints. The current study showed that DART-TOFMS metabolomic fingerprinting represents a rapid and powerful analytical strategy enabling differentiation of common carp muscles according to feeding history by recording metabolomic fingerprints of ionizable components under the conditions of ambient MS.
Rapid determination of polycyclic aromatic hydrocarbons (PAHs) in tea using two-dimensional gas chromatography coupled with time of flight mass spectrometry
Talanta, 2012
A simple, fast, and cost effective sample preparation procedure has been developed and validated ... more A simple, fast, and cost effective sample preparation procedure has been developed and validated for the determination of 15+1 European Union Polycyclic Aromatic Hydrocarbons (15+1 EU PAHs) in dried tea leave samples. Based on a critical assessment of several sample extraction/clean-up approaches, the method based on the ethyl acetate extraction followed by the use of PAHs dedicated cartridges with molecularly imprinted polymers (MIPs) has been found as an optimal alternative in terms of time demands and obtained good extract purity. For the final identification/quantification of target PAHs, two dimensional gas chromatography coupled to a time-of-flight mass spectrometry (GC×GC-TOFMS) was used. The performance characteristics of the overall analytical method for individual PAHs determined at three spiking levels (0.5, 2.5 and 5 μg kg(-1)) were in following ranges: limits of quantitation (LOQs) 0.05-0.2 μg kg(-1), repeatabilities 2-9%, and recoveries 73-103%. The recoveries achieved by the newly developed sample preparation procedure when employed for naturally contaminated sample ("incurred" PAHs) were comparable to those obtained by other routinely used approaches employing sonication and/or pressurised liquid extraction for sample analytes isolation. The validated method was subsequently used for the determination of selected genotoxic PAHs in 36 samples of black and green tea obtained from the Czech retail market. The levels of ΣPAH4 (sum of benzo[a]anthracene (BaA), chrysene (CHR), benzo[b]fluoranthene (BbFA) and benzo[a]pyrene (BaP)) in black and green tea leaves ranged from 7.4 to 700 μg kg(-1) and from 4.5 to 102 μg kg(-1), respectively. Contamination of tested tea samples by BaP was in the range of 0.2-152 μg kg(-1).
Analysis of chlorophenoxy acids and other acidic contaminants in food crops
Science of The Total Environment, 1993
Several chlorophenoxy acids and chlorinated phenols were determined by means of gas chromatograph... more Several chlorophenoxy acids and chlorinated phenols were determined by means of gas chromatography in contaminated samples of cereals. Extraction of plant matrix with acetone/water mixture followed by alkaline hydrolysis was proved to be suitable for isolation of both free and conjugated residues. The use of pentafluorobenzyl bromide for volatilization of analytes, despite of enhanced ECD response, cannot be recommended for routine analysis. Methylation with either methanol/sulphuric acid or methanol/BF3 reagent can substitute diazomethane-based esterification procedure. Mass fragmentography provided the highest selectivity of detection, moreover good sensitivity--5 ppb--was achieved in this way. Even methyl derivatives of monochlorinated analytes could be, contrary to GC/ECD analysis, quantitated at this level.
Food Control, 2013
Application of solid phase extraction and two-dimensional gas chromatography coupled with time-of... more Application of solid phase extraction and two-dimensional gas chromatography coupled with time-of-flight mass spectrometry for fast analysis of polycyclic aromatic hydrocarbons in vegetable oils, Food Control (2013),
Production of apple-based baby food: changes in pesticide residues
Food Additives & Contaminants: Part A, 2014
Apples represent the main component of most fruit-based baby food products. Since not only fruit ... more Apples represent the main component of most fruit-based baby food products. Since not only fruit from organic farming, but also conventionally grown fruit is used for baby food production, the occurrence of pesticide residues in the final product is of high concern. To learn more about the fate of these hazardous compounds during processing of contaminated raw material, apples containing altogether 21 pesticide residues were used for preparation of a baby food purée both in the household and at industrial scale (in the baby food production facility). Within both studies, pesticide residues were determined in raw apples as well as in final products. Intermediate product and by-product were also analysed during the industrial process. Determination of residues was performed by a sensitive multi-detection analytical method based on liquid or gas chromatography coupled with mass spectrometry. The household procedure involved mainly the cooking of unpeeled apples, and the decrease of residues was not extensive enough for most of the studied pesticides; only residues of captan, dithianon and thiram dropped significantly (processing factors less than 0.04). On the other hand, changes in pesticide levels were substantial for all tested pesticides during apple processing in the industrial baby food production facility. The most important operation affecting the reduction of residues was removal of the by-products after pulping (rest of the peel, stem, pips etc.), while subsequent sterilisation has an insignificant effect. Also in this case, captan, dithianon and thiram were identified as pesticides with the most evident decrease of residues.
Polycyclic aromatic hydrocarbons and halogenated persistent organic pollutants in canned fish and seafood products: smoked versus non-smoked products
Food Additives & Contaminants: Part A, 2013
Assessment of pesticide residues in strawberries grown under various treatment regimes
Food Additives & Contaminants: Part A, 2013
The dynamics of pesticide residues in strawberries that involved quantification of pesticide resi... more The dynamics of pesticide residues in strawberries that involved quantification of pesticide residues in ripe fruits after model treatment was evaluated in repeated field trials conducted over 3 years. Sixteen commercial pesticide formulations in various combinations were employed in applications from 7 to 44 days before harvest. Altogether 21 active ingredients and some of their metabolites were determined in treated strawberries using LC-MS and GC-MS methods. Except for propargite, the concentrations of all active ingredients declined below the respective MRLs (Regulation (EC) No. 396/2005); nevertheless, most of the tested fungicides often persisted above the 0.01 mg kg⁻¹ limit required by baby food producers to avoid the risk of exceeding the 'baby food limit' established in Commission Directive 2006/141/EC. On the other hand, residues of the majority of tested insecticides, namely spinosad, pymetrozine, deltamethrin, lambda-cyhalothrin and azadirachtin, declined below this limit.
Food Additives and Contaminants, 2007
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Papers by Vladimír Kocourek