Safety of oleochemical products derived from beef tallow or bone fat regarding prions

Abstract

Bovine bone fat and beef tallow are widely used as raw material for oleochemical processes. Due to high temperature and pressure these processes are supposed to have an excellent inactivation potential for prions, i.e. the agent of BSE and other transmissible spongiform encephalopathies. To experimentally prove the destruction of the pathogenic prion protein aggregates under technically relevant conditions, oleochemical processes were emulated in the laboratory in reduced scale. Fat samples were spiked with highly infectious ex vivo prion rods and aliquots were taken before and after the processes. From these aliquots, undegraded prion protein was precipitated and determined by a sensitive Western blot assay. Degradation factors of 2 ?103 - 104 for catalytic fat hydrogenation and 107 for fat hydrolysis represent acceptable safety limits. With these experimental prion protein degradation factors the risk of human exposure to oleochemical products of bovine origin can be assessed. Assuming worst-case scenarios, the annual risk for human consumption of hydrogenated beef tallow is less than 6.8 x 10-7 and for skin application of fatty acid derivatives is less than 7.0 x 10-10. Both values are smaller than the background risk of contracting sporadic Creutzfeldt-Jakob disease (1 x 10-6 per annum).