Determination of biogenic amines in food samples using derivatization followed by liquid chromatography/mass spectrometry

A liquid chromatography (LC)/mass spectrometry method was developed for the determination of selected biogenic amines in various fish and other food samples. It is based on a precolumn derivatization of the amines with succinimidylferrocenyl propionate under formation of the respective amides and their reversed-phase liquid-chromatographic separation with subsequent electrospray ionization mass-spectrometric detection. Deuterated putescine, cadaverine, and histamine are added prior to the derivatization as internal standards that are coeluted, thus allowing excellent reproducibility of the analysis to be achieved. Depending on the analyte, the limits of detection were between 1.2 and 19.0 mg/kg, covering between 2 and 3 decades of linearity. The limit of detection and the linear range for histamine are suitable for the surveillance of the only defined European threshold for biogenic amines in fish samples. Compared with the established ortho-phthalaldehyde (OPA)/LC/fluorescence method, the newly developed method allows an unambiguous identification of the biogenic amines by their mass spectra in addition to only retention times, a fivefold acceleration of the separation, and independency from the sample matrix owing to the isotope-labeled internal standards. Various fish, calamari, and salami samples were successfully analyzed with the new method and validated with an independent OPA/LC/fluorescence method.     

Poly(cyclooctene)-based monolithic columns for capillary high performance liquid chromatography prepared via ring-opening metathesis polymerization

Monolithic columns for capillary HPLC were prepared via ring-opening metathesis polymerization (ROMP) from cis-cyclooctene (COE), tris(cyclooct-4-enyl-1-oxy)methylsilane (CL) as monomers, 2-propanol and toluene as porogens and RuCl(2)(Py)(2)(IMesH(2))(CHC(6)H(5)) (Py=pyridine, IMesH(2)=1,3-dimesityl-4,5-dihydroimidazolin-2-ylidene) as initiator within the confines of 200 microm i.d. fused silica columns. For evaluation of the novel monolithic capillary HPLC columns, a protein standard consisting of six proteins in the molecular weight range of 5800-66000 g/mol, i.e. ribonuclease A, insulin, albumin, lysozyme, myoglobin and beta-lactoglobulin, was used. Reproducibility of synthesis was checked by determining the relative standard deviation (RSD) in retention times (t(R)), which was found to be in the range of 2.9-3.9% for all analytes. Variations in polymer kinetics were realized by adding different amounts of free pyridine and had a significant influence on the monolith's morphology, the backpressure and retention times. On the contrary, variations in monomer content and COE to CL ratio showed only minor changes on these parameters. Long-term stability of 1000 runs at 50 degrees C showed excellent stability of the columns and no significant alteration in separation performance was observed in combination with slightly decreased retention times (approx. 1.6-7.2% for all analytes).     

Theoretical Considerations about Near-Wall Turbulence and Resulting Flow Control Schemes

Based on analytical considerations about how near-wall turbulence needs to be modified in order to reduce the momentum loss towards solid walls and to yield lower energy losses, a mechanism of turbulent drag reduction is proposed. This mechanism suggests that drag reducing flow control at high Reynolds numbers should be designed to minimize the turbulent dissipation rate. A previously published approach on how a reduction of the turbulent dissipation in the near-wall region can be achieved is analyzed further. The obtained results provide some new insight on the parameters that need to be considered when designing flow control schemes for skin friction drag reduction. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

A study on thorium levels in human femur bones

The incorporation of naturally occurring thorium isotopes in human femur bones was studied by analyzing 28 bone samples. The results show that the activity concentrations of ²³²Th and ²³⁰Th are in the range of the blank values resulting in an upper limit of theirs activity concentrations in human bones. The presence of ²²⁸Th can be attributed, on the basis of model calculations, to the radioactive decay of deposited ²²⁸Ra. We conclude that thorium is not detectably incorporated into human bones.     

Polysaccharide functionality through extrusion processing

Extrusion processing is a technology applied in the food and pharmaceutical industry for affecting product microstructure, product chemistry or the macroscopic shape of products. Starch based products are often extruded to break down the starch granule to render it digestible and to produce a shaped product. Encapsulation of flavors, nutrients and drugs is another frequent application of extrusion processing. This short review article is concerned with the use of extrusion processes to modify polysaccharide functionality. Extrusion processes are applied to polysaccharides for specific purposes such as physical modification or chemical modification (reactive extrusion), manufacture of confectionary gels and encapsulation of flavors or drugs. Non-starch polysaccharides and confectionary gels have also been extruded. Another application area is in the field of dietary fibers, obtained through extrusion processing of by- or waste-products of the food industry. The focus of this article is on extruding starch and other polysaccharides as an ingredient rather than as part of a final food product obtained by extrusion processing. It concludes with a discussion on extrusion as microstructure generating process and the relevance of this application to taste perception in semi-liquid foods.