Qualitative and quantitative detection of CNS in meat products via GC/MS and GFAP ELISA-comparison of methods

To protect the consumer from the pathogenic agent of the transmissible spongiform encephalopathies (TSE), the regulation 999/2001 defines specified risk materials (SRM), which must be removed from feedstuff and the food chain. Especially, tissues of the central nervous system (CNS), originating from cattle, sheep and goat, over the age of 12 months, are counted as SRM. In this study, two methods for CNS detection were compared regarding to the quality of CNS detection. The detection of Glial Fibrillary Acid Protein (GFAP) by means of an ELISA and the analysis of CNS typical fatty acids (FA) by means of Gas Chromatography/Mass Spectrometry (GC/MS) were developed at the Institute of Food Hygiene, Both methods were examined for the quality of CNS detection. As parameters for the validation intermediate precision, accuracy and recovery were chosen. For this study, internal and external reference materials with three different heating steps (85 degrees C, 115 degrees C and 133 degrees C) were analysed. Both methods correctly identified all CNS-negative samples. False positive results were not detected. Based on the actual state of law, a categorisation of SRM was carried out by the GC-MS method. All SRM positive samples could be identified correctly. Intermediate precision of both methods was comparable to previously published data of CNS detection methods based on GFAP-ELISA (Schmidt et al., 2001; Hossner et al., 2006; Schebo(R) Biotech, 2007). Accuracy of both methods was given in samples heated up to 35 degrees C. Only the analysis of FA was in a position to detect the true CNS content in samples heated up to 115 'C and 133 'C. Recovery of the GFAP-ELISA ranged from 0 to 83.8%, whereas the recovery of the GC/MS was good (74.9-86.4%).