Competitive enzyme-linked immunosorbent assay for quantitative detection of bovine blood in heat-processed meat and feed.

Animal blood is widely used as a functional additive in food and as a protein supplement in animal feed. Effective analytical methods are therefore needed to enforce labeling regulations for product quality control, as well as to address safety concerns. This study developed a monoclonal antibody (MAb)-based competitive enzyme-linked immunosorbent assay (ELISA) for quantitative detection of ruminant (bovine and ovine) blood in heat-processed meat and feedstuff. MAb BblH9 immunoglobulin G1, which recognizes a 12-kDa, thermostable, ruminant blood protein, was used as the detecting agent in the competitive ELISA. The immunoreactivity of MAb Bb1H9 was confirmed in both an indirect noncompetitive ELISA and a competitive ELISA, in which antigens are presented in immobilized form and free form, respectively. The competitive ELISA was optimized, and three spiked samples adulterated at 0 to 10% were tested to determine the detection limits of the optimized assay. Results showed that MAb Bb1H9 is specific to ruminant blood protein, with no cross-reaction with nonblood samples tested. The optimized competitive ELISA quantitatively detected heat-processed bovine blood over the tested range. The detection limit of the assay for bovine blood in beef (P < 0.001), bovine blood in porcine blood (P < 0.01), and bovine blood meal in soybean meal (P < 0.01) was found to be 0.5% in all cases. This MAb-based competitive ELISA is thus suitable for the sensitive and quantitative detection of ruminant blood proteins in heat processed meat and feed products.