Betty G. M. Gortemaker

Evauation of lysinoalanine determinations in food proteins

ZusammenfassungUm zwei Bestimmungsmethoden von Lysinoalanin (LAL) miteinander zu vergleichen, wurden Analysen sowohl mit einem automatischen. Aminosäureanalysator als auch mit Dünnschichtchromatographie-Densitometrie, mit verschiedenen in den Niederlanden käuflichen Lebensmitteltypen und Ingredienten durchgeführt.Daraus ergibt sich eine ziemlich gute Übereinstimmung im LAL-Gehalt nach beiden Methoden. Einige Resultate deuten jedoch darauf hin, daß eine einzelne Methode nicht immer eindeutig ist, was die Identität der auf Ninhydrin positiv reagierenden Verbindung, bei gleicher Position im Chromatogramm als LAL angesprochen, betrifft.In Hefe z. B. fand man mit Dünnschichtchromatographie einen Gehalt von etwa 800 mg LAL/kg Protein, mit dem Aminosäurenanalysator jedoch kein LAL. Auch in erhitzter Milch und Milchprodukten ist der LAL-Gehalt, bestimmt mit Dünnschichtchromatographie, höher als der mit dem Aminosäurenanalysator gefundene Wert. Die Ursache ist, daß bei der Dünnschichtchromatographie von erhitzten Milchprodukten eine unbekannte auf Ninhydrin positiv reagierende Verbindung dem LAL-Fleck vorangeht, der praktisch mit dem LAL zusammenfällt. Um Störung durch unbekannte Verbindungen dieser Art beim Aminosäurenanalysator zu vermeiden, kann man eine geeignete Elutionstemperatur wählen. Bei einigen Schaummitteln jedoch erhält man durch Temperaturveränderung keine gute Trennung.SummaryA comparison is made between lysinoalanine (LAL) determinations both with an automatic amino acid analyzer (AAA) and with thin layer chromatography-densitometry (TLC) in different types of food and food ingredients, taken from the Dutch market.Generally there is a reasonable agreement between the LAL content obtained by both methods. However, some results indicate that a single technique is not always conclusive about the real identity of the ninhydrin-positive compound at the same position as LAL on the chromatogram. By TLC for instance, in yeast a content of about 800 mg of LAL/kg in protein is found, but according to the AAA method no LAL is present. In heated milk and milk products the LAL content determined by the TLC method is also higher than that found by the AAA method.This is caused by a preceding unknown ninhydrinpositive compound in TLC, occurring in all heated milk products and practically coinciding with LAL. In the AAA technique similar interferences of unknown ninhydrin-positive compounds could be avoided by choosing a suitable elution temperature; however, application of this temperature modification to foaming agents gave no satisfactory results.

Reduction of extended-spectrum-β-lactamase- and AmpC-β-lactamase-producing Escherichia coli through processing in two broiler chicken slaughterhouses

Whilst broilers are recognised as a reservoir of extended-spectrum-β-lactamase (ESBL)- and AmpC-β-lactamase (AmpC)-producing Escherichia coli, there is currently limited knowledge on the effect of slaughtering on its concentrations on poultry meat. The aim of this study was to establish the concentration of ESBL/AmpC producing E. coli on broiler chicken carcasses through processing. In addition the changes in ESBL/AmpC producing E. coli concentrations were compared with generic E. coli and Campylobacter. In two slaughterhouses, the surface of the whole carcasses was sampled after 5 processing steps: bleeding, scalding, defeathering, evisceration and chilling. In total, 17 batches were sampled in two different slaughterhouses during the summers of 2012 and 2013. ESBL/AmpC producing E. coli was enumerated on MacConkey agar with 1mg/l cefotaxime, and the ESBL/AmpC phenotypes and genotypes were characterised. The ESBL/AmpC producing E. coli concentrations varied significantly between the incoming batches in both slaughterhouses. The concentrations on broiler chicken carcasses were significantly reduced during processing. In Slaughterhouse 1, all subsequent processing steps reduced the concentrations except evisceration which led to a slight increase that was statistically not significant. The changes in concentration between processing steps were relatively similar for all sampled batches in this slaughterhouse. In contrast, changes varied between batches in Slaughterhouse 2, and the overall reduction through processing was higher in Slaughterhouse 2. Changes in ESBL/AmpC producing E. coli along the processing line were similar to changes in generic E. coli in both slaughterhouses. The effect of defeathering differed between ESBL/AmpC producing E. coli and Campylobacter. ESBL/AmpC producing E. coli decreased after defeathering, whereas Campylobacter concentrations increased. The genotypes of ESBL/AmpC producing E. coli (blaCTX-M-1, blaSHV-12, blaCMY-2, blaTEM-52c, blaTEM-52cvar) from both slaughterhouses match typical poultry genotypes. Their distribution differed between batches and changed throughout processing for some batches. The concentration levels found after chilling were between 10(2) and 10(5)CFU/carcass. To conclude, changes in ESBL/AmpC producing E. coli concentrations on broiler chicken carcasses during processing are influenced by batch and slaughterhouse, pointing to the role of both primary production and process control for reducing ESBL/AmpC producing E. coli levels in final products. Due to similar changes upon processing, E. coli can be used as a process indicator of ESBL/AmpC producing E. coli, because the processing steps had similar impact on both organisms. Cross contamination may potentially explain shifts in genotypes within some batches through the processing.

A rapid sample preparation method for the determination of sulfamethazine in swine tissues by high-performance liquid chromatography

ZusammenfassungBeschrieben wird ein schnelles Verfahren zur Bestimmung von Sulfadimidin in Muskel-und Nierengewebe des Schweines. Die Methode umfaßt Extraktion mit Dichlormethan, Reinigung des Extraktes mit einer Kombination von Silica- und Umkehrphasen C18 Sep-Pak-Kartuschen und Analyse durch Hochleistungs-Flüssigchromatographie auf einer Hypersil ODS-Säule, wobei Acetonitril/Ammoniumacetatlösung (10 mmol · 1−1, pH 6,8) 1 + 3 v/v als mobile Phase fungiert. Die Messung wird bei 254 nm vorgenommen. Bei Zusatzmengen von 0,05 bis 0,5 μg Sulfadimin pro g waren die Wiederfindungsraten aus Schweinemuskel- und -nierengewebe 89,5 bzw. 80,5%. Auch nach intramuskulärer Injektion Sulfadimidins wurden die Rückstände in den oben bereits genannten Geweben bestimmt. Die Anwendung von Ultraschall-Energie zur Extraktion von Sulfadimidin aus tierischen Geweben wird diskutiert.SummaryA rapid procedure for the determination of sulfamethazine in swine muscle and kidney is described. The method comprises sonication-aided extraction with dichloromethane, cleaning-up of the extract on a combination of silica and reversed-phase C18 Sep-Pak cartridges and analysis by high-performance liquid chromatography on a Hypersil ODS column using acetonitrile/ammonium acetate solution (10 mmol · 1−1, pH 6.8) 1 + 3 v/v as the mobile phase. Detection was performed at 254 nm. Mean recoveries of added sulfamethazine from swine muscle and kidney, at levels of 0.05 to 0.5 μg · g−1, were 89.5 and 80.5%, respectively. After intramuscular injection of sulfamethazine into swine, residues in tissues were also determined. The application of ultrasonic energy for the extraction of sulfamethazine residues from animal tissues is also discussed.

Automated Enzymatic Determination of Glycogen in Bovine Muscle Tissue

ZusammenfassungEine automatische Methode zur enzymatischen Bestimmung des Glykogens im Rindfleisch wird beschrieben. Glykogen wurde durch Amyloglucosidase (EC 3.2.1.3) bei pH 4,6 hydrolysiert. Die erhaltene Glucose wurde dialysiert und mit Hexokinase (EC 2.7.1.1) und Glucose-6-phosphat-dehydrogenase (EC 1.1.1.49) behandelt. Das gebildete NADPH wurde bei 340 nm spektrophotometrisch gemessen.Das System gibt lineare Meßergebnisse im Bereich von 0–500 μg Glykogen per ml. Diese Methode ermöglicht 45 Proben pro Std zu untersuchen.SummaryAn automated method is described for the enzymatic determination of glycogen in meat. Glycogen was hydrolyzed by amyloglucosidase (EC 3.2.1.3) at pH 4.6. The glucose released was separated by dialysis and then determined with hexokinase (EC 2.7.1.1) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49). The NADPH formed was measured spectrophotometrically at 340 nm. The system produced a rectilinear response in the glycogen range of 0–500 μg/ml. The analyses could be performed at a rate of fourthy-five samples per hour.

Automated enzymatic determination of starch in meat products

ZusammenfassungEine automatische Methode zur enzymatischen Bestimmung der Stärke in Fleischerzeugnissen wird beschrieben. Nach Lösung in einer Dimethylsulfoxide/Salzsäure-Mischung, wurde Stärke mittels Amyloglucosidase (EC 3.2.1.3) and Hexokinase (EC 2.7.1.1)/Glukose-6-phosphatdehydrogenase (EC 1.1.1.49) mit Hilfe des Technicon AutoAnalyzers II automatisch bestimmt. Diese Methode ermöglicht 40 Proben pro Std. zu untersuchen. Die Ergebnisse stimmen gut mit den Analysenwerten der polarimetrischen Bestimmung überein.SummaryAn automated method is described for the enzymatic determination of starch in some meat products. After solubilization with dimethylsulfoxide/hydrochloric acid, the starch was automatically determined with amyloglucosidase (EC 3.2.1.3) and hexokinase (EC 2.7.1.1)/glucose-6-phosphate dehydrogenase (EC 1.1.1.49) using a Technicon AutoAnalyzer II System. The analyses could be performed at a rate of forty samples per hour. The results agree very well with those obtained by the polarimetric method.

Automated enzymatic determination of ATP in bovine muscle tissue

ZusammenfassungEine automatische Methode zur enzymatischen Bestimmung des Adenosin-5′-triphophats (ATP) im Rindfleisch mit Hexokinase (EC 2.7.1.1) und Glucose-6-phosphate-dehydrogenase (EC 1.1.1.49) im Bereich von 0-115 Vg ATP per ml wird beschrieben. Das gebildete NADPH wurde bei 340 nm spektrophotometrisch gemessen. Mit dieser Methode ist es mög-lich, 40 Proben pro Std zu untersuchen.SummaryAn automated method is described for the enzymatic determination of adenosine-5′-triphosphate (ATP) in meat using hexokinase (EC 2.7.1.1) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49) in the range of 0–115 μg/ml. The NADPH formed is measured spectrophotometrically at 340 nm. ATP can be analysed at a rate of forty samples per hour.