Aflatoxin B1 and its interconverting metabolite aflatoxicol in milk: the situation in Mexico

Between 1996 and 1998, 580 litres of milk in Mexico were surveyed for aflatoxin B1 (AFB1) and its metabolite aflatoxicol (AFL), which are mutagenic and carcinogenic mycotoxins that interconvert AFB1-AFL-AFB1. The seven most consumed brands from different regions of Mexico included pasteurized and ultrapasteurized milk with four different fat levels: whole fat (28-33 g l-1), half-skimmed (10-20 g l-1), light (1-4 g l-1) and with vegetable oil (33 g l-1). Aflatoxins in each sample were concentrated with total aflatoxin immunoaffinity columns and quantitated by high-performance liquid chromatography. A milk sample was considered contaminated if it contained ≥0.05 μg l-1 AFL. Pasteurization and ultrapasteurization of milk did not control contamination with AFL, which was present in 13% of samples at ≥0.05 μg l-1 and in 8% at ≥0.5 μg l-1, with a range of AFL from 0 to 12.4 μg l-1. AFB1 was present mainly in traces (0-0.4 μg l-1). The safest milk in relation to AFL contamination was imported milk powder with vegetable oil. There was a significant correlation between contamination of milk with AFL and the autumn (p<0.0002); the fat content was not significant.