Quantitative evaluation of pork adulteration in raw ground beef by radial immunodiffusion and enzyme-linked immunosorbent assay

Quantitative estimates are important to establish whether pork adulteration in ground beef is accidental or intentional. A standard agar gel radial im munodiffusion (RID) test using forensic-grade antiserum to porcine albumin and an enzyme-linked immunosorbent assay (ELISA) using forensic-grade anti- porcine glycoprotein immunoglobulin were used to determine from 1 to 75% ra w pork in raw ground beef. The RID test, which incorporated 1.5% anti-pork serum in 1% immunodiffusion agar, formed precipitin rings with pork albumin in agar wells. A Linear standard curve was obtained by plotting the diffus ion area against standard pork concentrations ranging from 0 to 80%. For th e ELISA the endpoint optical density increased linearly versus log % pork b etween 0.0625% and 2% pork. In spiked samples, the RID test had a detection limit of 3 to 5%, a coefficient of variation (CV) of 22%, and a recovery o f 105%. The ELISA had a detection limit of 1%, a CV of 18%, and a recovery of 114%. The mean recovery from the spiked samples by the ELISA and RID tes t was not significantly different (P > 0.05) from the known sample amounts. Quantitation by RID of 28 ground beef samples (27 of which were DTEK ELISA -positive for pork adulteration) revealed a wide range of pork content, wit h values as high as 48%.