RESUMEN
The method in which to discriminate between genetically modified (GM) versus non-modified foodstuffs is based on the presence of newly introduced genes at the protein or DNA level. Current available methods are almost exclusively based on the polymerase chain reaction (PCR). This procedure consists of three steps: DNA isolation, the amplification of the desired DNA fragment and visualisation of the obtained amplification products. The first and crucial step is the DNA isolation. Due to several processing steps, the quality of the extracted DNA may be damaged, rendering PCR analysis, and therefore GMO detection, impossible. In this study, the DNA quality of soy lecithin in margarines has been evaluated by PCR. For this purpose, DNA was isolated from margarines with different levels of lecithin with two different extraction methods, including the CTAB method proposed by the European Committe for Standardization (CEN). The amplification of soy DNA by PCR resulted to be difficult, which could be explained by the difficult DNA extraction from margarine and the low lecithin content.
Asunto(s)
ADN/aislamiento & purificación , Contaminación de Alimentos/análisis , Alimentos Modificados Genéticamente , Lecitinas/análisis , Margarina/análisis , Reacción en Cadena de la Polimerasa/métodos , Proteínas de Soja/análisis , ADN/análisis , Lecitinas/genética , Proteínas de Soja/genéticaAsunto(s)
ADN de Plantas/aislamiento & purificación , Alimentos Modificados Genéticamente , Plantas Modificadas Genéticamente , Aceite de Soja/genética , ADN de Plantas/análisis , Europa (Continente) , Contaminación de Alimentos/análisis , Etiquetado de Alimentos , Tecnología de Alimentos , Legislación Alimentaria , Reacción en Cadena de la Polimerasa , Sensibilidad y EspecificidadRESUMEN
The manner in which to discriminate between genetically modified (GM) versus non-modified foodstuffs is based on the presence of newly introduced genes at the protein or DNA level. Current available methods are almost exclusively based on the polymerase chain reaction (PCR). These methods consist of three steps: DNA isolation, amplification of the desired DNA fragment and visualisation of the obtained amplification products. The first and crucial step is the DNA isolation. In this study three different methods are described for the isolation of DNA from chocolate, two of which are commercial kits. The results indicate that both kits, in contrast with the non-commercial method, are suitable for the isolation of DNA from chocolate, provided that the adapted PCR conditions are applied.
Asunto(s)
Cacao/química , ADN/aislamiento & purificación , Contaminación de Alimentos/análisis , Alimentos Modificados Genéticamente , Glycine max/genética , ADN/análisis , Reacción en Cadena de la Polimerasa/métodosRESUMEN
The photobleaching of fluorescence emission during confocal laser scanning was studied on well-defined, stained objects [microspheres of polystyrene or fluorescent gels of fluorescein isothiocyanate (FITC)-labeled dextran] and on biological samples. X,Y laser scanning with confocal microscopy induces fundamental differences in exposure rate and time in different z-planes orthogonal to the optical axis. A heterogeneous bleaching rate was observed at different focal levels in the polystyrene spheres and in the gels. This phenomenon can be caused by refractive index differences or is correlated with a photobleaching rate, which is dependent not only on the excitation light intensity but also on the photon flux (total intensity per unit of time). Heterogeneous excitation induced by refractive index differences results in photobleaching differences but will not necessarily cause heterogeneous emission intensity. Altered emission originating from altered excitation will be annihilated if the emitted light returns to the image plane along the same inverse path, compensating for the proportional increase or decrease in excitation intensity with an increased or decreased emission intensity. High numerical aperture or increased scanning speed increases the photobleaching rate. This leads to the conclusion that photobleaching in confocal scanning laser microscopy is dependent on photon energy flux density (joule/m2s).