Preanalytical Sample Preparation and Analyte Extraction

Sample preparation methods aim at separation of the target cells or virus particles from the surrounding food matrix. Down-stream methods, such as cell disruption, analyte purification, and detection via, for example, real-time PCR, have to be taken into consideration individually when designing or choosing a suitable preparation method. Sample treatment is defined as the preanalytical step in the method protocol, which is also necessary for reduction of the sample volume while maintaining the initial target number, as much as possible. This chapter first describes optimal performance characteristics of sample preparation. Next, the chapter talks about practical solutions to physical separation methods, biochemical and biological separation methods. Then, it discusses chemical and enzymatic digestion of the food sample matrix for preseparation. Analyte extraction is the subsequent step following sample preparation. It is necessary to obtain access to the molecules that are the target of molecular detection assays such as real-time PCR. In order to gain access to the analyte molecules, nucleic acids, or proteins, the integrity of the target cells has to be destroyed in most cases. Since analyte extraction as a part of the detection chain in food pathogen detection is similar to the application in basic research, a brief summary is given.