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Rentsch J.,Swiss Quality Testing Services SQTS | Weibel S.,Official Food Control Authority of the Canton Zurich | Ruf J.,Official Food Control Authority of the Canton Thurgau | Eugster A.,Cantonal Office of Consumer Protection Aargau | And 2 more authors.
European Food Research and Technology | Year: 2013

Milk products like yogurt, flavoured milk-drinks, curd and cheese may be composed of milk different from cow, namely of ruminant species like sheep and goat. Such products experience an increasing demand in Europe and are recognised as healthy and naturally finished specialities. To verify declared milk compositions in these dairy products, two different quantitative multiplex PCR systems have been evaluated in a comparison test with eleven participating laboratories employing two unknown, traditionally manufactured cheeses with different degrees of ripening to determine milk fractions from cow, ewe and goat. Precision and accuracy was investigated by calibration to dilutions of DNA mixtures and to homologous matrix-adapted reference cheeses, respectively. As expected, independent of the particular method, best inter- and intra-laboratory accuracy has been achieved through the use of homologous reference cheese standards. Furthermore, it has been shown that cheese ripening and the concomitant DNA degradation exert an inverse effect on the method's sensitivity and performance characteristics. Additionally, a broad market survey of different milk products demonstrated its applicability as an efficient analytical tool for food control laboratories to challenge the authenticity of milk and its products from small ruminants. © 2012 Springer-Verlag Berlin Heidelberg. Source


Koppel R.,Official Food Control Authority of the Canton of Zurich | Eugster A.,Cantonal Office of Consumer Protection Aargau | Ruf J.,Official Food Control Authority of the Canton Thurgau | Rentsch J.,Swiss Quality Testing Services SQTS
Journal of AOAC International | Year: 2012

The quantification of meat proportions in raw and boiled sausage according to the recipe was evaluated using three different calibrators. To measure the DNA contents from beef, pork, sheep (mutton), and horse, a tetraplex real-time PCR method was applied. Nineteen laboratories analyzed four meat products each made of different proportions of beef, pork, sheep, and horse meat. Three kinds of calibrators were used: raw and boiled sausages of known proportions ranging from 1 to 55% of meat, and a dilution series of DNA from muscle tissue. In general, results generated using calibration sausages were more accurate than those resulting from the use of DNA from muscle tissue, and exhibited smaller measurement uncertainties. Although differences between uses of raw and boiled calibration sausages were small, the most precise and accurate results were obtained by calibration with fine-textured boiled reference sausages. © 2012 Publishing Technology. Source


Koppel R.,Official Food Control Authority of the Canton Zurich | Ruf J.,Official Food Control Authority of the Canton Thurgau | Rentsch J.,Swiss Quality Testing Services SQTS
European Food Research and Technology | Year: 2011

Meat products are often composed of more than one meat species. A quantitative multiplex PCR was developed to determine the proportion of meat fractions of beef, pork, horse and sheep. The precision and accuracy were investigated by dilutions of DNA from all four species and examining different meat products from the market. Application of this tetraplex quantitative real-time PCR system will enable official food control and production control laboratories to efficiently investigate the composition of meat products. © 2010 Springer-Verlag. Source


Koppel R.,Official Food Control Authority of the Canton of Zurich | Rentsch J.,Swiss Quality Testing Services SQTS | Ruf J.,Official Food Control Authority of the Canton Thurgau | Eugster A.,Cantonal Office of Consumer Protection Aargau | And 4 more authors.
Chimia | Year: 2014

To elucidate the capability of laboratories to determine allergen contents, an international interlaboratory trial was conducted using meat products spiked with 12 allergens. The measurement uncertainty was calculated independent of the applied method simulating realistic situations when comparing analysis certificates from different laboratories. The measurement uncertainty was revealed to be in the best cases +/-100%, in the worst cases quantification exhibited a measurement uncertainty of higher than 200% making quantitative analysis impossible. The measurement uncertainty seemed to depend on the analyte and assays used. © Schweizerische Chemische Gesellschaft. Source

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