Aflatoxin M₁ in cheese: situation on the Slovak market

Aflatoxin M₁ (AFM₁), which is a hydroxylated metabolite of aflatoxin B₁, can be irreversibly bound to casein micelles and thus, its higher content is measured in cheese than in the original milk. The present study describes validation of a reliable and rapid method for AFM₁ content determination in cheese applied to 36 kinds of cheese sold in Slovakia during the spring of 2024. The method consisted of three basic steps: extraction of AFM₁ from cheese, purification of extracts using immunoaffinity columns, and determination of AFM₁ content by high performance liquid chromatography with fluorescence detection. Suitability of the method was proved by the limits of detection and quantification equal to 2.0 and 6.0 ng/kg, respectively, which is in accordance with the limits set by European legislation for analytical procedures for AFM₁ determination in milk. Accuracy of the method was determined using a recovery test, spiking cheese with AFM₁, and varied between 87.8 and 100.5 %. Precision was confirmed by low relative standard deviations, 0.3—7.9 %, and Hor- Rat values (0.01—0.32) of the results obtained on different days. Experiments showed the AFM₁ content in all cheese to be below the limit of quantification, which indirectly confirmed the absence of AFM₁ in milk as raw material. However, AFM₁ contamination of milk is expected to increase due to global warming in future; therefore, AFM₁ contamination should be an essential part of current food safety issues.