Aflatoxin M1, in pasteurized and ultrapasteurized milk with different fat content in Mexico

High per capita milk consumption in Mexico indicated a strong need for documentation of aflatoxin M-1 (AFM(1)) levels in milk. A survey of 580, 2-liter samples (n = 290), was conducted to quantify AFM(1) using high-performance liquid chromatography, considering two maximum tolerance levels (0.05 and 0.5 mug/liter). We relate aflatoxin levels in the seven most consumed brands from different regions, with two processes (pasteurized and ultrapasteurized), different expiration dates, and different fat content: whole fat (28, 30, and 33 g), half-skimmed (10, 16, and 20 g), light (1, 2, and 4 g), and with vegetable oil. Pasteurization and ultrapasteurization did not diminish AFM(1) contamination present at levels of 0 to 8.35 mug/liter in 40% of the milk samples at concentrations greater than or equal to0.05 mug/liter and in 10% of the samples at greater than or equal to0.5 mug/liter. Statistically significant relationships were AFM(1) contamination with brand (P = 0.002 at the greater than or equal to0.05 mug/liter level and P = 0.034 at the greater than or equal to0.5 mug/ liter level) and higher AFM(1) levels with mild or warm seasons of the year (P = 0.0003). Samples with greater fat content had slightly more probability (P = 0.067) of being contaminated by AFM(1) at the greater than or equal to0.5 mug/liter level. The milk with the lowest contamination of AFM(1) was a brand imported as powder and rehydrated in Mexico.