Detection of aflatoxin M1 in milk products from China by ELISA using monoclonal antibodies

A rapid and sensitive indirect competitive enzyme-linked immunosorbent assay (ELISA) method using monoclonal antibody for measuring aflatoxin M1 (AFM1) in milk and milk products has been described. One monoclonal antibody was isolated and characterized after fusion of myeloma cells with spleen cells isolated from BALB/c mice that had been immunized with AFM1 carboxymethyl oxime conjugated with bovine serum albumin (BSA). Cross-reactivities of the anti-AFM1 monoclonal antibody clone were 100, 13.9, 6.7 and <1% against AFM1, aflatoxin B1 (AFB1), aflatoxin G1 (AFG1) and deoxynivalenol (DON), respectively. Assays of milk samples mixed with AFM1 ranging in concentration from 0.1 to 3.2 ng/ml gave mean ELISA recovery of 98%. The limit of detection concentration of AFM1 was 0.04 ng/ml. AFM1 contamination was measured in 12 samples of raw milk, 15 samples of powdered milk, 104 samples of liquid milk and four cheese samples collected from different supermarkets in Northeast of China. Of 135 milk samples tested, 55 (41%) samples contained AFM1 at levels that ranged from 0.32–0.50 ng/ml, 24 (18%) samples contained 0.16–0.32 ng/ml, and 18 (13%) samples contained 0–0.16 ng/ml; in 38 (28%) samples AFM1 was not detected. The results indicate that the necessary precaution will have to be taken to minimize the AFM1 contamination in milk and milk products from Northeast of China.