An indirect competitive ELISA for the detection of cows’ milk and caseinate in goats’ and ewes’ milk and cheese using polyclonal antibodies against bovine γ-caseins

 An indirect competitive enzyme-linked immunosorbent assay (ELISA) method was developed for the detection of bovine milk and caseinate in goats’ and ewes’ milk and cheese. Polyclonal antibodies were raised in rabbits and chickens against bovine γ3-casein. In a first affinity chromatography step, antibodies recognizing caseins were absorbed on bovine casein-Sepharose. From the dialysed eluate, antibodies crossreacting with ewes’ and goats’ milk protein were completely removed by immunoadsorption onto stationary phases containing ovine casein and protein extracted from genuine ewes’ and goats’ milk cheese. The detection limit of the ELISA test was 0.1% and the method was applied successfully during an EU collaborative study of the evaluation of methods for the detection of cows’ milk.