detection and quantification of almond (Prunus dulcis) in food with ELISA

Abstract: Reliable methods to analyze food for the presence of almond are important – not only for those allergic to almond, but also for monitoring the compliance with labelling regulations (EG directive 2003/89). Until now the Swedish National Food Administration has used methods like rocket immunoelectrophoresis and real-time PCR to detect almond in food. These methods are, however, not sensitive enough for protecting the most sensitive individuals. Therefore, the performance of a commercial ELISA kit was tested with regard to specificity/cross reactivity and limit of detection for almond both in solution and in different matrixes. The limit of quantitation was at least 3,1 ppm (mg/kg) in solution and similar concentrations were measured in bisquits and chocolate. The ELISA method was about 100-fold more sensitive than rocket immunoelectrophoresis and PCR. The specificity of the test kit was evaluated against a number of different nuts and seeds. No important cross reactivity was found. The antibodies against almond used in the kit can not differentiate between almond and apricot kernel. For such purposes the PCR method could be used.