A COMPETITIVE ENZYME-LINKED-IMMUNOSORBENT-ASSAY FOR DETECTION OF BOVINE-MILK IN-OVINE AND CAPRINE MILK AND CHEESE USING A MONOCLONAL-ANTIBODY AGAINST BOVINE BETA-CASEIN

A competitive ELISA (enzyme-linked immunosorbent assay) was performed to detect and quantify bovine milk in ovine and caprine milk and chees e using a monoclonal antibody (AH4 MAb) against bovine beta-casein. Ov ine or caprine mill; and cheese containing bovine milk were added simu ltaneously with the AH4 MAb to the wells of a microtiter plate that ha d been previously sensitized with commercial bovine beta-casein. The b ovine caseins in milk or cheese samples compete with the bovine beta-c asein bound to the plate for the AH4 MAb binding sites. Further immuno recognition of AH4 MAb bound to the bovine beta-casein immobilized ont o the plate was attained with rabbit anti-mouse immunoglobulin conjuga ted to peroxidase. Subsequent enzymic conversion of the substrate show ed clear differences in absorbance values during assay of mixtures of ovine and caprine milk and cheese containing various amounts of bovine milk. The competitive ELISA developed in this work allows the quantit ative detection of bovine milk in ovine and caprine milk and cheese sa mples in the range of 0.5 to 25% of substitution.