Dependence of the 12-methyltridecanal concentration in beef on the age of the animal

The content of 12-methyltridecanal (12-MT), which contributes greatly to the characteristic aroma of stewed beef, was determined by a stable isotope dilution assay in meat samples from nine bovine animals of different ages. The results, which were related to the amount of phospholipids (PL), indicate that 12-MT content increases with the age of beef, e. g. from 36 g·g^–1 PL in a 4-monthold calf to 810 g·g^–1 PL in an 8-year-old cow. The increase of 12-MT content in PL per month varied between 8.4 and 10.9 g·g^–1 PL (mean: 9.3 ± 0.78 g·g^–1 PL). Possibly 12-MT content is suitable as an indicator for the estimation of the age of a beef sample.

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Abhängigkeit der 12-Methyltridecanal-Konzentration in Rindfleisch vom Alter des Tieres

Zusammenfassung 12-Methyltridecanal (12-MT), das zum charakteristischen Aroma von geschmortem Rindfleisch wesentlich beiträgt, wurde durch Isotopenverdünnungsanalyse in Proben aus neun Rindern unterschiedlichen Alters bestimmt. Die Ergebnisse, die auf den Phospholipid (PL)-Gehalt bezogen wurden, zeigen, daß das 12-MT mit dem Alter des Rindes ansteigt, z.B. von 36 g·g^–1 PL bei einem 4 Monate alten Kalb auf 810 g·g^–1 PL in einer 8 Jahre alten Kuh. Der Anstieg des 12-MT in den PL pro Monat schwankte zwischen 8,4 und 10,9 g·g^–1 (Mittelwert 9,3 ±0,78 g·g^–1). Möglicherweise ist das 12-MT als Indikator für die Altersbestimmung von Rindfleisch geeignet.

     

Adsorption of organophosphates into microporous and mesoporous NaX zeolites and subsequent chemistry

Due to the neurotoxicity of organophosphate (OP) pesticides and nerve agents synthesized as military or terror agents, their safe destruction and disposal is of considerable current importance. A representative OP, trimethyl phosphate (TMP), was adsorbed onto NaX zeolite, two mesoporous modifications, and a low-silica X zeolite. The nucleophilic chemical reactions of TMP with the zeolites were investigated by solid-state 13C and 31P nuclear magnetic resonance (NMR) and the solvent extracts by 1H, 13C, and 31P NMR. Nucleophilic substitution and subsequent hydrolysis reaction schemes are proposed. All of the zeolites have similar TMP decomposition yields, supporting the hypothesis that slow or incomplete diffusion of TMP in the microporous zeolite regions limits TMP decomposition.     

Methods used for the isolation, enumeration, characterisation and identification of Enterococcus spp. 2. Pheno- and genotypic criteria

This paper reviews the methodology applied for the identification and characterisation of enterococci and covers phenotypic, genotypic and phylogenetic techniques. Although conventional phenotypic typing schemes are useful for rapid and simple identification of enterococcal species for routine applications, other methods like standardised sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE), multilocus enzyme electrophoresis (MLEE), antimicrobial susceptibility testing, serotyping, pyrolysis mass spectrometry (pyMS) and vibrational spectroscopic methods allow a more in-depth characterisation of enterococci. Many of the recently described enterococcal species exhibit deviations from hitherto so-called classical enterococci with regard to their phenotypical properties. Therefore, genotypic methods have to be used to clarify their possible assignment to the genus Enterococcus. In this review, special emphasis is given on recently developed polymerase chain reaction (PCR)-based typing methods such as random amplified polymorphic DNA (RAPD), amplified fragment length polymorphism (AFLP), specific and random amplification (SARA) and modifications of PCR-ribotyping as well as pulsed-field gel electrophoresis (PFGE) and partial sequence analysis. The use of PCR and probes for genus and species identification of enterococci is also considered like the application of sequence data of conserved DNA regions (e.g., ribosomal ribonucleic acid (rRNA) genes) in the case of species identification.     

Trypsin inhibitor activity of soybean as affected by genotype and fertilisation

The presence of protease inhibitors in soybean prohibits the utilisation of the raw beans for food and feed. However, little information is available about environmental influences and the effects of nitrogen and sulphur supply on the antinutritional constituents of soybean. As these factors may influence protease inhibitors, soybean genotypes segregated according to the presence or absence of the Kunitz trypsin inhibitor have been evaluated for trypsin inhibitor activity (TIA) in field trials. TIA was affected significantly by environment (geographical location), fertilisation treatment and genotype. Environmental means of TIA were between 69.5 and 104.8 mg g^?1. Nitrogen application, which caused an increase in seed protein content, resulted in a reduction in TIA by about 15% as compared with the control. Remarkably, simultaneous application of nitrogen and sulphur in the form of ammonium sulphate had a similar reductive effect on TIA to that of nitrogen application alone, although soybean protease inhibitors are rich in sulphur amino acids. Significant genetic variation in TIA was found both within the genotype class with the Kunitz inhibitor present as well as within the class lacking this inhibitor. The results suggest that TIA of soybean may be modified considerably by genetic improvement and appropriate agronomic management. Copyright © 2003 Society of Chemical Industry     

Processing and analytical characterisation of pulp-enriched cloudy apple juices

Pulp-enriched cloudy apple juices were manufactured from two apple varieties by blending of apple puree with natural cloudy apple juice in order to enrich bioactive secondary plant substances. Finishing of the puree with a 0.6-mm mesh screen and final product homogenisation revealed as the optimum processing technology for the novel 100% fruit beverage. The presence of large particles originating from the puree prevented long-term cloud stability, but due to the proportion of cloud-stable juice a complete phase separation did not occur. Optimal drinkability was achieved at a viscosity of 11.5 mPa s. Polyphenol compositions and concentrations were determined by means of RP-HPLC/PDA. The results ranged from 109 to 610 mg/l. All samples showed the typical polyphenol pattern of apples with dominating hydroxycinnamic acids followed by flavanols and flavonols. The puree addition to the cloudy apple juices increased the polyphenol concentrations by average 100%. Relatively, the highest increase could be observed for dimeric procyanidins. Different technological variants did not affect significantly the polyphenol concentrations. The dietary fibre contents of the pulp-enriched cloudy apple juices ranged from 5.8 to 9.4 g/l.     

Occurrence of benzene as a heat-induced contaminant of carrot juice for babies in a general survey of beverages

A survey of benzene contamination of 451 beverage samples, using headspace sampling combined with gas chromatography and mass spectrometry (HS-GC/MS) with a quantification limit of 0.13 microg l(-1), was conducted. Artefactual benzene formation during headspace sampling was excluded by gentle heating at 50 degrees C only and adjustment of sample pH to 10. The incidence of benzene contamination in soft drinks, beverages for babies, alcopops and beer-mixed drinks was relatively low, with average concentrations below the EU drinking-water limit of 1 microg l(-1). Significantly higher concentrations were only found in carrot juice, with the highest levels in carrot juice specifically intended for infants. About 94% of 33 carrot juice for infants had detectable benzene levels, with an average concentration of 1.86 +/- 1.05 microg l(-1). Benzene contamination of beverages was significantly correlated to iron and copper concentrations, which act as catalyst in benzene formation. The formation of benzene in carrot juice was predominantly caused by a heat-induced mechanism, which explains the higher levels in infant carrot juices that are subject to higher heat-treatment to exclude microbiological contamination.     

Expression profiles of effector proteins SopB, SopD1, SopE1, and AvrA differ with systemic, enteric, and epidemic strains of Salmonella enterica

The presence and expression of sopB, sopD1, sopE1, and avrA genes encoding virulence associated effector proteins were studied comparatively in 405 Salmonella enterica strains. They belong to different serovars and clonal types (genotypes, phage types) and originated from different clinical (systemic infection, focal enteritis, enterocolitis) and epidemic sources (epidemics, sporadic cases). The sopB and sopD1 determinants were commonly prevalent, but sopE1 and avrA genes only in 55% and 80%, respectively. A correlation of this pattern of absence and presence of the respective genes to the epidemic and clinical origin could not be detected. In contrast, the expression of the respective genes appeared differently: SopB and SopE1 proteins are well produced, but SopD1 and AvrA proteins only rarely under the applied standard culture conditions. However, using a range of different environmental signals (temperature, pH, cations, etc.) some of the S. enterica nonproducer strains (e. g., S. Agona, S. Bovismorbificans, S. Virchow, etc.) begin to produce AvrA and SopD1. They turned now into an expression profile which was found typically for the epidemic strains of S. Typhimurium and S. Enteritidis. Also S. enterica strains from systemic infections could be characterized by their strong SopB and SopE1 expression while SopD1 and AvrA proteins were missing. Although it is premature to outline generally a correlation of these expression profiles and the clinical and epidemiological potency of Salmonellae, the reported results allow a first understanding how a fine tuning of their virulence will take place.     

A new method to determine the ratio of electricity production from fossil and biogenic sources in waste-to-Energy plants

New directives of the European Union require operators of waste-to-energy (WTE) plants to report the amount of electricity that is produced from renewable sources in the waste feed. Until now, the standard method to determine the portion of renewable electricity is sorting the wastes into defined fractions of fossil organic and biogenic waste components and determining the lower heating value of these fractions. Out of it the amount of electricity production from renewables is calculated. This practice is labor and cost intensive. Therefore, it is usually carried out once a year which provides only a snapshot analysis of limited significance. This paper proposes a method to calculate the portion of electricity produced from renewable materials in waste continuously by solving a set of equations. All data required are either available from literature or from operating data routinely measured in WTE plants. The advantages are statistically derived uncertainty of the result, temporal resolution of the result down to daily mean values, low implementation efforts, and virtually no operational costs. An example of the implementation of the method to a 60 000 tons per year WTE plant is given.