Development of Analytical Methods for Determination and Monitoring of Levels of Aflatoxin M1 in Dairy Products Collected from Markets in South Korea

Introduction:  Aflatoxin M₁ (AFM₁), a 4-hydroxy derivative of aflatoxin B₁, is formed from aflatoxin B₁ by cytochrome P450 in liver and excreted into milk of animals that have been fed with aflatoxin B₁-contaminated feeds. Since AFM₁, a Group1 human carcinogen, is stable during food processing, it could pose a health risk to public.

Purpose:  The purpose of this study was to develop sensitive and reproducible analytical methods for determination of AFM₁ in milk, yoghurt, and cheese by using high performance liquid chromatography-fluorescence detection (HPLC-FLD) after immunoaffinity column clean-up and to monitor the levels of AFM₁in the dairy samples collected from markets in South Korea.

Methods: The linearity, recovery, repeatability, and reproducibility of the analytical methods were assessed for AFM₁ analysis using HPLC-FLD after toxin purification by immunoaffinity columns. The levels of AFM₁ in a total of 224 dairy samples including milk, yoghurt, and cheese were determined using the established analytical methods. The AFM₁ in the dairy samples was confirmed by liquid chromatography-mass spectrometry (LC-MS/MS).

Results: The analytical method showed high linearity (r² ≥ 0.999) for AFM₁ in the range of 0.05–10.00 µg/l. The limits of detection of the methods for AFM₁ were 0.001 µg/l in milk, 0.02 µg/l in yoghurt, and 0.015 g/kg in cheese, respectively. The recovery of AFM₁ in the dairy products was 83-108% along with 2.1-12.8% of repeatability and 0.0-13.1% of reproducibility. The occurrence of AFM₁ was 55% in the total of 224 dairy samples collected from South Korea. Low levels of AFM₁ (0.001-0.136 µg/l) below 0.5 µg/l of the legal limit of the level of AFM₁ in milk were detected in the dairy samples.

Significance: The levels of AFM₁ in dairy products did not pose a significant health risk to public in South Korea.