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Friedrichsdorf, Germany

Steinbach P.,Central Laboratories Friedrichsdorf | Schwack W.,University of Hohenheim
Journal of Chromatography A | Year: 2014

SPE cartridges of different anion exchange materials and florisil were compared regarding their efficiency to remove free fatty acids from ethylacetate/cyclohexane (1:1) extracts, their elution profiles and recovery rates for 38 representative pesticides, their contribution to an elevated background during gas chromatography-mass spectrometry (GC-MS), and on possible matrix effects caused by the cartridge material itself. From the seven tested cartridges, only Varian PSA (PSA) and Silicycle SiliaPrep Diamine (SPD) were very well able to retain fatty acids from ethylacetate/cyclohexane solutions and provided satisfying recoveries and elution profiles for the tested pesticides. Thus, with both cartridges a fast and simple cleanup was developed and tested with 86 pesticides as well as with EN 12393 GPC extracts of oat flour. The SPE cleanup clearly improved the identification of pesticides and reduced false negative findings due to retention time shifts and superimpositions of quantifier and/or qualifier ions. As compared with dispersive SPE it was shown, that depending on the amount of sorbent the cleanup efficiency was comparable, but recoveries were generally better for cartridge SPE procedures. © 2013 Elsevier B.V. Source


Boulais C.,Danone Research | Wacker R.,Central Laboratories Friedrichsdorf | Augustin J.-C.,National Veterinary School of Alfort | Ben Cheikh M.H.,Danone Research | Peladan F.,Danone Research
Journal of Food Protection | Year: 2011

Mycobacterium avium subsp. paratuberculosis (MAP) is the causal agent of paratuberculosis (Johne's disease) in cattle and other farm ruminants. The potential role of MAP in Crohn's disease in humans and the contribution of dairy products to human exposure to MAP continue to be the subject of scientific debate. The occurrence of MAP in bulk raw milk from dairy herds was assessed using a stochastic modeling approach. Raw milk samples were collected from bulk tanks in dairy plants and tested for the presence of MAP. Results from this analytical screening were used in a Bayesian network to update the model prediction. Of the 83 raw milk samples tested, 4 were positive for MAP by culture and PCR. We estimated that the level of MAP in bulk tanks ranged from 0 CFU/ml for the 2.5th percentile to 65 CFU/ml for the 97.5th percentile, with 95% credibility intervals of [0, 0] and [16, 326], respectively. The model was used to evaluate the effect of measures aimed at reducing the occurrence of MAP in raw milk. Reducing the prevalence of paratuberculosis has less of an effect on the occurrence of MAP in bulk raw milk than does managing clinically infected animals through good farming practices. © International Association for Food Protection. Source


Zhu S.,Central Laboratories Friedrichsdorf | Zhu S.,Justus Liebig University | Schnell S.,Justus Liebig University | Fischer M.,Central Laboratories Friedrichsdorf
Food Microbiology | Year: 2013

Cronobacter is associated with outbreaks of rare, but life-threatening cases of meningitis, necrotizing enterocolitis, and sepsis in newborns. This study was conducted to determine the effect of organic acids on growth of Cronobacter in laboratory medium and reconstituted powdered infant formula (PIF) as well as the bacteriostatic effect of slightly acidified infant formula when combined with neonatal gastric acidity. Inhibitory effect of seven organic acids on four acid sensitive Cronobacter strains was determined in laboratory medium with broth dilution method at pH 5.0, 5.5 and 6.0. Acetic, butyric and propionic acids were most inhibitive against Cronobacter in the laboratory medium. The killing effect of these three acids was partially buffered in reconstituted PIF. Under neonatal gastric acid condition of pH 5.0, the slightly acidified formula which did not exert inhibition effect solely reduced significantly the Cronobacter populations. A synergistic effect of formula moderately acidified with organic acid combined with the physiological infant gastric acid was visible in preventing the rapid growth of Cronobacter in neonatal stomach. The study contributed to a better understanding of the inhibitory effect of organic acids on Cronobacter growth in different matrixes and provided new ideas in terms of controlling bacteria colonization and translocation by acidified formula. © 2013 Elsevier Ltd. Source


Zhu S.,Central Laboratories Friedrichsdorf | Zhu S.,Justus Liebig University | Ratering S.,Justus Liebig University | Schnell S.,Justus Liebig University | Wacker R.,Central Laboratories Friedrichsdorf
Journal of Food Protection | Year: 2011

Twenty-two isolates of the family Enterobacteriaceae, with focus on Cronobacter isolated from infant formula and the environment of milk powder plants, were comparatively identified using API 32E (bioMérieux, Marcy l'Etoile, France), 16S rRNA gene sequencing (Accugenix, Newark, USA), and matrix-assisted laser desorption and ionization-time-of-flight mass spectrometry (MALDI-TOF MS; Mabritec, Riehen, Switzerland and AnagnosTec, Potsdam, Germany). With API 32E, 22% of the isolates were assigned to species, 64% were assigned to a genus, and 14% could not be discriminated at any taxonomic level. Both 16S rRNA gene sequencing and MALDI-TOF MS assigned 100% of the isolates to species, but the identifications based on MALDI-TOF MS results were more discriminating and unequivocal. Our data indicate that MALDI-TOF MS provides the most rapid and unambiguous identification of Cronobacter and closely related Enterobacteriaceae isolates. Copyright © International Association for Food Protection. Source


Zhu S.,Central Laboratories Friedrichsdorf | Zhu S.,Justus Liebig University | Schnell S.,Justus Liebig University | Fischer M.,Central Laboratories Friedrichsdorf
International Journal of Food Microbiology | Year: 2012

Cronobacter spp. is an important release test parameter for powered infant formula (PIF). An impedance method is proposed for the rapid detection of this pathogen in PIF. An impedance based method (BacTrac 4300 Microbiological Analyzer) combined with a RNA hybridisation assay (RiboFlow™) was evaluated using 23 strains in PIF samples and compared to a culture based reference method (ISO/TS 22964). The influences of competitive flora, heat and dry stress on the reliability of the impedance method were investigated. Seven different Cronobacter species were included in the evaluation, among them are strains with high susceptibility to low pH and high temperatures. Compared to the reference method, a higher sensitivity (85%) and specificity (100%) was observed using the impedance method, combined with the commercial rRNA based lateral flow test kit as a confirmation tool. The detection time was substantially shortened by using the impedance technique and RiboFlow™. Cronobacter could be detected within maximally 29. h, while the reference method takes up to five days when including confirmation of positive results. © 2012 Elsevier B.V. Source

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