Comparison of Real-Time PCR Quantification Methods in the Identification of Poultry Species in Meat Products.

Poultry meat is consumed worldwide and is prone to food fraud because of large price differences among meat from different poultry species. Precise and sensitive analytical methods are necessary to control poultry meat products. We chose species-specific sequences of the cytochrome b gene to develop two multiplex real-time polymerase chain reaction (real-time PCR) systems: one for chicken (Gallus gallus), guinea fowl (Numida meleagris), and pheasant (Phasianus colchicus), and one for quail (Coturnix japonica) and turkey (Meleagris gallopavo). For each species, added meat could be detected down to 0.5 % w/w. No cross reactions were seen. For these two real-time PCR systems, we applied three different quantification methods: (A) with relative standard curves, (B) with matrix-specific multiplication factors, and (C) with an internal DNA reference sequence to normalize and to control inhibition. All three quantification methods had reasonable recovery rates from 43% to 173%. Method B had more accepted recovery rates, i.e., in the range 70-130%, namely 83% compared to 75% for method A or C.

Influence of Smoking and Barbecuing on the Contents of Anthraquinone (ATQ) and Polycyclic Aromatic Hydrocarbons (PAHs) in Frankfurter-Type Sausages.

The contents of anthraquinone (ATQ) and polycyclic aromatic hydrocarbons (anthracene (ANT) and PAH4) in smoked Frankfurter-style sausages were investigated depending on various smoking conditions. During smoking, the smoke generator, the smoking duration, the type of wood, and some more plant-specific parameters were tested. The sausages were also barbecued on a charcoal grill. The lowest mean contents of all analytes were observed when friction smoke was used (ATQ < limit of quantification (LOQ); ANT < LOQ; PAH4 < limit of detection (LOD)) and the highest when the settings of ventilations flaps were changed (ANT 36.3 µg/kg; PAH4 2.2 µg/kg) or at an intensive smoke density (ATQ 3.2 µg/kg). The contents increased with the smoking time, but irregularities were detected after 10 min. The use of different types of wood had no influence on the ATQ content but affected the PAH content. In barbecued samples, ATQ and ANT contents were detected at the level of friction smoke and maximum PAH4 contents were found above the exposure during smoking. Due to the varying influence of the smoking parameters on the two analytes, there was no direct correlation between the contents of ATQ and ANT in all smoking experiments.

A sensitive HPLC-MS/MS method for the simultaneous detection of microbial transglutaminase, and bovine and porcine fibrinogen/thrombin in restructured meat.

A sensitive HPLC-MS/MS method for the simultaneous detection of microbial transglutaminase (TG) from Streptomyces mobaraensis, and bovine and porcine fibrinogen/thrombin in restructured meat was developed using tryptic marker peptides of TG (five markers), and bovine and porcine fibrinogen (six markers each). Meat binding experiments with beef and pork were performed using a technical TG mixture (Activa, Ajinomoto), and bovine and porcine plasmapowder FG (PPFG; Sonac B.V.). The method developed allows the simultaneous detection of the use of these cold-set binders in raw and heated samples. The peak areas of the fibrinogen marker peptides were increased by a factor of about 100, compared to blank values originating from the occurrence of residual blood in meat, using a concentration of 0.6% bovine and porcine PPFG. A differentiation between the use of blood plasma powder and PPFG using the ratios of fibrinogen to serotransferrin peptide peak areas seems to be possible.

Production of dry-cured formed ham with different concentrations of microbial transglutaminase: Mass spectrometric analysis and sensory evaluation.

Dry-cured formed hams were produced with different concentrations of microbial transglutaminase (TG; 0.05, 0.1, 0.2, 0.5, and 0.8% Activa PB) and glucono-delta-lactone as control. A sensory evaluation was performed during a 43-day storage to determine cohesion, cavities, and local separation of dry-cured formed ham. Rising TG concentrations resulted in a slight increase in the evaluation of all sensory parameters, whereas amounts of TG higher than 0.5% led to an only very minor improvement. Dry-cured formed ham samples were analyzed by a sensitive HPLC-MS/MS method for the detection of TG using five tryptic marker peptides. Even very small amounts of Activa PB (0.05%) were detectable unambiguously. A decrease of TG detectability during the storage time of dry-cured formed ham was not observed. Using four marker peptides, no false-positive or -negative results were obtained. The amounts of two marker peptides were calculated using isotope-labeled peptides. They showed high correlations to the amount of Activa PB (R2>0.995).

A sensitive high performance liquid chromatography-tandem mass spectrometry method for the detection of microbial transglutaminase in different types of restructured meat.

A sensitive HPLC-MS/MS-method for the detection of microbial transglutaminase (TG) from Streptomyces mobaraensis in different types of restructured meat (pork, beef, chicken, and turkey) was developed using six tryptic marker peptides (8-11 amino acids). Meat binding experiments were performed with two technical TG mixtures with and without caseinate. After optimization of the conditions of extraction and tryptic digestion, restructured meat and blank values (total samples: 62) were analyzed in a raw and heated state. By investigation of samples pre-treated with oil marinade, emulsion marinade, seasoning salt as well as breadcrumbs, only very little effects of the type of pre-treatment on the detectability of TG were found. Using four marker peptides, no false-positive or false-negative results were obtained. The limit of detection (LOD) was about a factor of 10 below the recommended amount of transglutaminase for raw as well as heated restructured meat.

Polycyclic aromatic hydrocarbons (PAH) and phenolic substances in meat products smoked with different types of wood and smoking spices.

The contents of polycyclic aromatic hydrocarbons (15+1 EU PAH) and phenolic substances (guaiacol, 4-methylguaiacol, syringol, eugenol, and trans-isoeugenol) were investigated in smouldering-smoked Frankfurters and mini-salamis. For the 51 smoking experiments wood chips of oak, poplar, hickory, spruce, fir, alder, beech, and beech with an apple-smoking spice mix, cherry-smoking spice mix, and a mix of juniper berries and bay leaves were tested. The use of poplar and hickory led to a decrease in the PAH contents in the range of 35-55% compared to the commonly used beech wood. Higher PAH contents by using softwood were not observed. The use of the rapidly growing poplar seems to be a reasonable approach for reducing the PAH contents in smoked meat products. Furthermore, the sum contents of the five phenolic substances in sausages smoked with poplar were higher, or only slightly lower, when compared to the use of beech.

Contents of polycyclic aromatic hydrocarbons (PAH) and phenolic substances in Frankfurter-type sausages depending on smoking conditions using glow smoke.

The contents of polycyclic aromatic hydrocarbons (PAH) and phenolic substances in Frankfurter-type sausages were investigated depending on hot smoking conditions (glow smoke). For the 24 smoking experiments (performed in duplicates) three different smoke densities and ventilator velocities as well as wood chips with five different moisture contents were tested. During the smoking process, concentrations of O(2), CO(2) and CO, humidity and temperature in the smoking chamber as well as smoke generation temperature were determined. The chemical analysis included the contents of the 15+1 EU priority PAH and the phenolic substances guaiacol, 4-methylguaiacol, syringol, eugenol and trans-isoeugenol. The smoking conditions had a significant influence on smoke generation temperature, organoleptic properties and the formation of PAH and phenolic substances. The PAH contents increased with smoke density and ventilator velocity. No correlation between the contents of PAH and phenols was observed.

Heavy metal residues in beef carcasses in Beni-Suef abattoir, Egypt.

A total of 300 samples were collected from cattle slaughtered in the Beni-Suef abattoir in Egypt. Samples included muscle, liver and kidney. Animals were randomly selected from the slaughter line. The age of the slaughtered cattle was less than three years (18-30 months). Samples were packed separately in plastic bags, identified and stored at -18°C until analysis which was performed at the Max Rubner Institute in Kulmbach, Germany, for the following heavy metals residues: lead, cadmium, mercury, arsenic, chromium and nickel in beef muscle, liver and kidney samples. The results revealed that the overall mean residual levels of lead were 8.77 µg/kg, 42.70 µg/kg and 109.42 µg/kg fresh weight in muscle, liver and kidney samples, respectively, while the mean residual levels of cadmium were 1.40 µg/kg, 14.16 µg/kg and 62.56 µg/kg fresh weight, respectively, and the mean arsenic residual levels were 5.06 µg/kg, 4.64 µg/kg and 14.92 µg/kg fresh weight, respectively. The mean residual levels of mercury were 3.91 µg/kg, 5.81 µg/kg and 10.14 µg/kg fresh weight, respectively, and the residual levels of chromium were 11.20 µg/kg, 21.85 µg/kg and 25.49 µg/kg fresh weight, respectively. Finally, the mean residual levels of nickel were 21.17 µg/kg, 14.59 µg/kg and 34.95 µg/kg fresh weight, respectively. The mean values of all heavy metals examined were low and did not exceed the permissible limits adopted by different organisations. Most heavy metals accumulated in higher concentrations in the kidney in comparison to the liver and muscle.