Seasonal patterns of aflatoxin M1 contamination in commercial pasteurised milk from different areas in Thailand

Aflatoxin M₁ (AFM₁) levels were determined in pasteurised milk from five commercial trademarks produced in different areas in Thailand. One hundred and twenty milk samples were collected from local markets in Chiang Mai province, Thailand, to evaluate AFM₁ concentrations using immunoaffinity columns and high-performance liquid chromatography with fluorescence detection. The overall median AFM₁ level was 0.023?µg?L^?1 ranging from 0.004 to 0.293?µg?L^?1. All trademarks had average AFM₁ concentrations lower than 0.05?µg?L^?1, with those in Trademarks 3 to 5 being higher than Trademarks 1 and 2 (P?1, even though operating in the same area. However, only Trademark 3 showed significant differences of AFM₁ levels between seasons. The results suggested that farm management factors, rather than environment factors, were likely to be the main cause of AFM₁ contamination in dairy products.