Occurrence of aflatoxin M₁ in randomly selected North African milk and cheese samples

Abstract

Forty-nine samples of raw cow's milk and 20 samples of fresh white soft cheese were collected directly from 20 local dairy factories in the north-west of Libya and analysed for the presence of aflatoxin M₁ (AFM₁). The samples were analysed using a high-performance liquid chromatography technique for toxin detection and quantification. Thirty-five of the 49 milk samples (71.4%) showed AFM₁ levels between 0.03 and 3.13 ng ml⁻¹ milk. Multiple analyses of five milk samples free of AFM₁ artificially contaminated with concentrations of AFM₁ at 0.01, 0.05, 0.1, 1.0 and 3.0 ng ml⁻¹ showed average recoveries of 66.85, 72.41, 83.29, 97.94 and 98.25%, with coefficients of variations of 3.77, 4.11, 1.57, 1.29 and 0.54%, respectively. Fifteen of 20 white soft cheese samples (75.0%) showed the presence of AFM₁ in concentrations between 0.11 and 0.52 ng g⁻¹ of cheese. Multiple assays of five cheese samples free of AFM₁ spiked with different concentration of AFM₁ (0.1, 0.5, 1.0 and 3.0 ng g⁻¹) showed average recoveries of 63.23, 78.14, 83.29 and 88.68%, with coefficients of variation of 1.53, 9.90, 4.87 and 3.79%, respectively. The concentrations of AFM₁ were lower in the cheese products than in the raw milk samples.

Keywords:

• aflatoxin M1
• cheese
• milk
• immunoaffinity columns
• high-performance liquid chromatography (HPLC)

Acknowledgements

The authors thank Dr Mohamed Omer Mohamed, Department of Food Science, Al-Fateh University, Tripoli, Libya, for collaboration in the study.