A modified indirect ELISA procedure for raw meat speciation using crude anti‐species antisera and stabilised immunoreagents

Abstract

AbstractIndirect enzyme‐linked immunosorbent assay (ELISA) for species identification of unheated meat materials has been modified to facilitate the use of non‐specific (unpurified) anti‐species antisera by integral assay inhibition of heterologous cross‐reactivity. Effective ELISA treatments of three antisera (identifying beef, horse and pig) and four commercial products (identifying beef, horse, pig and sheep/goat) were determined using chequer‐board microtitration assays against pure species antigens. Subsequent tests with aqueous meat extracts gave consistent absorbance differences between the homologous (high colour) and heterologous (low colour) responses and provided reliable, accurate species identification without the extensive prior purification of antisera (i.e. by affinity chromatography) previously required. This modified ELISA enabled efficient use of stabilised anti‐species sera discs, prepared initially for application in a simplified agar‐gel immunodiffusion (AGID) test; i.e. one disc (20 μl freeze‐dried antiserum) for testing two meat samples by the prescribed AGID made sufficient treated solution to test 50 meat samples on microtitre plates. Authentic species meat extracts are also stabilised on discs for convenience (reference responses and routine controls). ELISA in this form is a practical alternative to AGID screening tests or can be used in parallel back‐up tests providing sensitive results in less than 3 h on a large or small scale.