Two real-time PCR methods for the relative quantitation of DNA from meat species in food samples are described: these methods are applicable for horse in processed beef meat products, and pork in raw/processed beef me...Two real-time PCR methods for the relative quantitation of DNA from meat species in food samples are described: these methods are applicable for horse in processed beef meat products, and pork in raw/processed beef meat products. Test samples were prepared using raw meat admixtures or processed horse/pork in beef food products made to an industry-standard recipe. The methods were subjected to single laboratory method validation, evaluating the performance characteristics of specificity, PCR efficiency and r-squared (r<sup>2</sup>), Limit of Detection (LOD), Limit of Quantitation (LOQ), and precision and trueness. A limited UK-based inter-laboratory trial of the two methods was completed involving four participating laboratories. Full statistical analysis of the data qualified the applicability of the methods for accurate and sensitive trace-level analysis. The methods were deemed fit for purpose for reproducibly distinguishing between adventitious contamination at 0.1% (w/w), the level for further enforcement action at 1% (w/w), and a level representative of deliberate economically motivated adulteration (10% (w/w)). The data provided evidence that the precision of the two methods was applicable for qualitative and quantitative detection at topically important levels of adulteration. This work has added significant value to the current state of the art in quantitative determination of topical meat species adulteration, allowing analysts to distinguish between adventitious contamination and deliberate adulteration. The resulting methods described in this paper can easily be deployed and used by analytical laboratories for controls and due-diligence testing based on standard laboratory equipment.展开更多
Excessive use of maleic anhydride(MAN)in starch production is potentially harmful for consumers’health.This study presents a macro-scale Raman chemical imaging method for detection and quantification of MAN particles...Excessive use of maleic anhydride(MAN)in starch production is potentially harmful for consumers’health.This study presents a macro-scale Raman chemical imaging method for detection and quantification of MAN particles mixed in starch powder.MAN was mixed into corn starch at eight concentration levels from 50 ppm to 6400 ppm(w/w).Each mixture was put in a sample holder with a 150 mm×100 mm area and a 2 mm depth to create a large surface and a thin layer of the powdery sample for inspection.A 30 W 785 nm line laser was projected on the sample surface,from which hyperspectral images were obtained by a line-scan Raman imaging system with a spatial resolution of 0.2 mm.Fluorescence signals generated by laser-sample interactions were eliminated by a mathematical baseline correction method.A unique Raman peak was selected at 1839 cm-1 for the MAN detection,at which single-band fluorescence-corrected images were extracted from the mixture of each concentration and used to generate chemical images for MAN detection and mapping.The MAN detection limit was estimated at 100 ppm based on the Raman imaging measurement results.Pixel concentrations of the MAN in the chemical images were found linearly correlated with mass concentrations of the MAN particles in the starch powder,suggesting the Raman chemical imaging method has the potential for quantitative detection of the MAN in the starch-MAN mixtures.展开更多
文摘Two real-time PCR methods for the relative quantitation of DNA from meat species in food samples are described: these methods are applicable for horse in processed beef meat products, and pork in raw/processed beef meat products. Test samples were prepared using raw meat admixtures or processed horse/pork in beef food products made to an industry-standard recipe. The methods were subjected to single laboratory method validation, evaluating the performance characteristics of specificity, PCR efficiency and r-squared (r<sup>2</sup>), Limit of Detection (LOD), Limit of Quantitation (LOQ), and precision and trueness. A limited UK-based inter-laboratory trial of the two methods was completed involving four participating laboratories. Full statistical analysis of the data qualified the applicability of the methods for accurate and sensitive trace-level analysis. The methods were deemed fit for purpose for reproducibly distinguishing between adventitious contamination at 0.1% (w/w), the level for further enforcement action at 1% (w/w), and a level representative of deliberate economically motivated adulteration (10% (w/w)). The data provided evidence that the precision of the two methods was applicable for qualitative and quantitative detection at topically important levels of adulteration. This work has added significant value to the current state of the art in quantitative determination of topical meat species adulteration, allowing analysts to distinguish between adventitious contamination and deliberate adulteration. The resulting methods described in this paper can easily be deployed and used by analytical laboratories for controls and due-diligence testing based on standard laboratory equipment.
文摘Excessive use of maleic anhydride(MAN)in starch production is potentially harmful for consumers’health.This study presents a macro-scale Raman chemical imaging method for detection and quantification of MAN particles mixed in starch powder.MAN was mixed into corn starch at eight concentration levels from 50 ppm to 6400 ppm(w/w).Each mixture was put in a sample holder with a 150 mm×100 mm area and a 2 mm depth to create a large surface and a thin layer of the powdery sample for inspection.A 30 W 785 nm line laser was projected on the sample surface,from which hyperspectral images were obtained by a line-scan Raman imaging system with a spatial resolution of 0.2 mm.Fluorescence signals generated by laser-sample interactions were eliminated by a mathematical baseline correction method.A unique Raman peak was selected at 1839 cm-1 for the MAN detection,at which single-band fluorescence-corrected images were extracted from the mixture of each concentration and used to generate chemical images for MAN detection and mapping.The MAN detection limit was estimated at 100 ppm based on the Raman imaging measurement results.Pixel concentrations of the MAN in the chemical images were found linearly correlated with mass concentrations of the MAN particles in the starch powder,suggesting the Raman chemical imaging method has the potential for quantitative detection of the MAN in the starch-MAN mixtures.
