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Biomedical subjects

Christoph von Holst

Publications and source records attributed to Christoph von Holst.

10 recordsLinked to original sources
PubMed2006

Effective PCR detection of animal species in highly processed animal byproducts and compound feeds.

In this paper we present a polymerase chain reaction (PCR)-based method for detecting meat and bone meal (MBM) in compound feedingstuffs. By choosing adequate DNA targets from an appropriate localisation in the genome, the real-time PCR method developed here proved to be robust to severe heat treatment of the MBM, showing high sensitivity in the detection of MBM. The method developed here permits the specific detection of processed pig and cattle materials treated at 134 degrees C in various feed matrices down to a limit of detection of about 0.1%. This technique has also been successfully applied to well-characterised MBM samples heated to as high as 141 degrees C, as well as to various blind feed samples with very low MBM contents. Finally, the method also passed several official European ring trials.

Animal Feed↗
PubMed2005

Discriminating animal fats and their origins: assessing the potentials of Fourier transform infrared spectroscopy, gas chromatography, immunoassay and polymerase chain reaction techniques.

The objective of the reported study was to assess the abilities of various methods to differentiate the sources of fats used in feedstuff formulations. The main target was the identification of tallow (ruminant fat) and its differentiation from non-ruminant fats. Four different techniques were compared in terms of their suitability for enforcing existing and upcoming legislation on animal by-products: (1) Fourier transform infrared spectroscopy (FT-IR) applied to fat samples, (2) gas chromatography coupled with mass spectrometry (GC-MS) to determine fatty acid profiles, (3) immunoassays focusing on the protein fraction included in the fat, and (4) polymerase chain reaction (PCR) for the detection of bovine-specific DNA. Samples of the different fats and oils as well as mixtures of these fats were probed using these analytical methods. FT-IR and GC-MS differentiated pure fat samples quite well but showed limited ability to identify the animal species or even the animal class the fat(s) belonged to; no single compound or spectral signal that could permit species identification could be found. However, immunoassays and PCR were both able to identify the species or groups of species that the fats originated from, and they were the only techniques able to identify low concentrations of tallow in a mixture of fats prepared by the rendering industry, even when the samples had been sterilised at temperatures >133 degrees C. Fats used in animal nutrition come mainly from the rendering industry, thereby confirming the suitability of PCR and immunoassays for their identification. However, neither of these latter techniques was able to detect "premier jus" tallow, representing the highest quality standard of fat with extremely low protein concentration.

Animals↗
PubMed2005

Detection of banned meat and bone meal in feedstuffs by near-infrared microscopic analysis of the dense sediment fraction.

In this paper we present an alternative method for detection of meat and bone meal (MBM) in feedstuffs by near-infrared microscopic (NIRM) analysis of the particles in the sediment fraction (dense fraction (d >1.62) from dichloroethylene) of compound feeds. To apply this method the particles of the sediment fraction are spread on a sample holder and presented to the NIR microscope. By using the pointer of the microscope the infrared beam is focussed on each particle and the NIR spectrum (1112-2500 nm) is collected. This method can be used to detect the presence of MBM at concentrations as low as 0.05% mass fraction. When results from the NIRM method were compared with the classical microscopic method, a coefficient of determination (R2) of 0.87 was obtained. The results of this study demonstrated that this method could be proposed as a complementary tool for the detection of banned MBM in feedstuffs by reinforcement of the monitoring of feeds.

Animal Feed↗
PubMed2004

Development of an extraction method for the determination of zearalenone in corn using less organic solvents.

A method for the determination of zearalenone in corn has been developed applying pressurised liquid extraction (PLE) and using environmentally acceptable and less noxious organic solvents. The extracted samples were analysed with liquid chromatography coupled to mass spectrometry (LC-MS) equipped with an electrospray (ESI) ionisation interface. The optimised extraction mixture was isopropanol and an aqueous solution of triethylamine (1%) 50:50 (v/v), which allowed to halve the use of organic solvent compared to the method proposed by ISO. When applying the optimised method to five different naturally contaminated corn samples the obtained concentrations were slightly increased compared to the analysis using the previously used extraction solvent (acetonitrile-methanol). The relative standard deviation (RSD, n = 3) varied between 4 and 10% depending on the concentration level of the target analyte in the test material.

Organic Chemicals↗
PubMed2003

Determination of zearalenone from wheat and corn by pressurized liquid extraction and liquid chromatography-electrospray mass spectrometry.

Zearalenone (ZON) was extracted from wheat and corn by using pressurized liquid extraction (PLE) and the PLE extracts were analyzed using liquid-chromatography-mass spectrometry (LC-MS) without further clean-up procedures. A statistical design approach was applied to evaluate the influence of several extraction parameters such as temperature (40 degrees C; 80 degrees C; 120 degrees C), time (5 min; 10 min) and solvent extraction mixture [acetonitrile-water (9:1, v/v); methanol-water (8:2, v/v); methanol-acetonitrile (1:1, v/v)] on fortified cereals. The results showed a strong influence of the solvent composition on recovery of ZON. Quantification of the analytes was performed by LC-MS analysis of the raw extract using matrix-matched standard curves. The method performance was tested in the selected conditions (80 degrees C; 5 min; two cycles; methanol-acetonitrile) on samples which had been previously used for an international proficiency test. Compared to the assigned value, the recovered ZON was 118% [relative standard deviation (RSD)=5.2%, n=3)] and 107% (RSD=2.2%, n=3) in wheat and corn, respectively. Therefore, PLE can be used for ZON extraction, achieving good performances and allowing for an automated handling of the sample extraction step. Successively, the influence of temperature and number of cycles was investigated on naturally contaminated corn. From these results it could be concluded that fortified experiments perfectly mimicked naturally contaminated samples.

Chromatography, Liquid↗
PubMed2003

Assessment of dietary exposure to some persistent organic pollutants in the Republic of Karakalpakstan of Uzbekistan.

A 1999 study heightened long-standing concerns over persistent organic pollutant contamination in the Aral Sea area, detecting elevated levels in breast milk and cord blood of women in Karakalpakstan (western Uzbekistan). These findings prompted a collaborative research study aimed at linking such human findings with evidence of food chain contamination in the area. An international team carried out analyses of organochlorine and organophosphate pesticides, polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) on samples of 12 foods commonly produced and consumed in Karakalpakstan. Analysis consistently detected long-lasting organochlorine pesticides and their metabolites in all foods of animal origin and in some vegetables such as onions and carrots--two low-cost components of many traditional dishes. Levels of PCBs were relatively low in all samples except fish. Analyses revealed high levels of PCDDs and PCDFs (together often termed "dioxins") in sheep fat, dairy cream, eggs, and edible cottonseed oil, among other foodstuffs. These findings indicate that food traditionally grown, sold, and consumed in Karakalpakstan is a major route of human exposure to several persistent toxic contaminants, including the most toxic of dioxins, 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD). Intake estimations demonstrate that consumption of even small amounts of locally grown food may expose consumers to dioxin levels that considerably exceed the monthly tolerable dioxin intake levels set by the World Health Organization. Data presented in this study allow a first assessment of the risk associated with the consumption of certain food products in Karakalpakstan and highlight a critical public health situation.

Dioxins↗
PubMed2002

Microwave-assisted extraction of zearalenone from wheat and corn.

A microwave-assisted extraction (MAE) method has been developed for determination of zearalenone in wheat and corn by LC-MS with an atmospheric pressure chemical ionization interface (APCI). Matrix effects were minimized by use of matrix-matched standard curves for quantification of the analyte. The limit of quantification (LOQ) of the method was 30 ng g(-1) in wheat and 20 ng g(-1) in corn. The rapid LC-MS method enabled analysis of the extracts without clean-up, thereby reducing analyte losses, the time required for the analytical procedure, and costs. A factorial design approach was used to examine the effect on extraction efficiency of the main extraction conditions - time, temperature, and solvent. On the basis of results from statistical assessment extraction was performed with 1:1 (v/v) methanol-acetonitrile at 80 degrees C for 5 min. When these extraction conditions were applied to a wheat sample from a recently conducted international proficiency test, 92% (103 ng g(-1)) of the assigned zearalenone concentration (112 ng g(-1)) in the test material was obtained. This result was within the uncertainty (u) range of the assigned value of the test material (u=+/-15.8 ng g(-1), alpha=0.05) thereby demonstrating the accuracy of the method was sufficient. The precision of the whole method was also confirmed to be adequate, because the observed relative standard deviation (RSD) of 12% (n=10) also fulfils the quality criteria recommended by European guidelines for in-house method validation.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Immunoaffinity column cleanup with liquid chromatography using post-column bromination for determination of aflatoxin B1 in cattle feed: collaborative study.

A collaborative study was conducted to evaluate the effectiveness of an immunoaffinity column cleanup liquid chromatography (LC) method for determination of aflatoxin B1 in cattle feed at a possible future European regulatory limit (1 ng/g). The test portion was extracted with acetone-water (85 + 15), filtered, diluted with water, and applied to an immunoaffinity column. The column was washed with water to remove interfering compounds, and the purified aflatoxin B1 was eluted with methanol. Aflatoxin B1 was separated and determined by reversed-phase liquid chromatography (RP-LC) and detected by fluorescence after post column derivatization (PCD) involving bromination. PCD was achieved with either pyridinium hydrobromide perbromide (PBPB), used by 14 laboratories, or an electrochemical cell and addition of bromide to the mobile phase, used by 7 laboratories. Both derivatization techniques were not significantly different when compared by the t-test; the method was statistically evaluated for all laboratories together (bromination and PBPB). The cattle feed samples, both spiked and naturally contaminated with aflatoxin B1, were sent to 21 laboratories in 14 different countries (United States, Japan, and Europe). Test portions were spiked at levels of 1.2 and 3.6 ng/g for aflatoxin B1. Recoveries ranged from 74 to 157%. Based on results for spiked samples (blind pairs at 2 levels) as well as naturally contaminated samples (blind pairs at 3 levels), the relative standard deviation for repeatability (RSDr) ranged from 5.9 to 8.7%. The relative standard deviation for reproducibility (RSDR) ranged from 17.5 to 19.6%. The method showed acceptable within- and between-laboratory precision for this matrix, as evidenced by HORRAT values, at the target levels of determination for aflatoxin B1. No major differences in RSD were observed, showing that the composition of the feeds was not a factor for the samples tested and that the method was applicable for all materials used.

Aflatoxin B1↗
PubMedDate not supplied

Determination of processed animal proteins, including meat and bone meal, in animal feed.

An intercomparison study was conducted to determine the presence of processed animal proteins (PAPs), including meat and bone meal (MBM) from various species, in animal feed. The performances of different methods, such as microscopy, polymerase chain reaction (PCR), immunoassays, and a protocol based on iquid chromatography (LC), were compared. Laboratories were asked to analyze for PAPs from all terrestrial animals and fish (total PAPs); mammalian PAPs; ruminant PAPs; and porcine PAPs. They were free to use their method of choice. In addition, laboratories using microscopy were asked to determine the presence of PAPs from terrestrial animals, which is applicable only to microscopy. For total PAPs microscopy, LC and some immunoassays showed sufficient results at a concentration as low as 0.1% MBM in the feed. In contrast, PCR was not fit for purpose. In differentiating between MBM from terrestrial animals and fishmeal, microscopy detected 0.5% of terrestrial MBM in feed in the presence of 5% fishmeal, but was less successful when the concentration of MBM from terrestrial animals was 0.1%. The animal-specific determination of MBM from mammals or, more specifically from either ruminants or pigs, by PCR showed poor results, as indicated by a high number of false-positive and false-negative results. The only PCR method that scored quite well was applied by a member of the organizer team of the study. Immunoassays scored much better than PCR, showing sufficient sensitivity but some deficiency in terms of specificity. The results also demonstrated that the reliable determination of MBM from ruminants has not been resolved, especially for low concentrations of MBM (0.1%) in feed. Comparison of the results for mammalian MBM from all methods indicated that, for control purposes, the immunoassay method, especially when applied as dipsticks, could be used as a rapid screening method combined with microscopy to confirm the positive samples. However, implementation of such a system would require that the immunoassays were previously validated to demonstrate that this approach is fit for purpose. The determination of ruminant or porcine PAPs by immunoassays was more difficult, partly because the MBM in this study contained about 50% bovine and porcine material, thereby reducing the target concentration level to 0.05%.

Animal Feed↗