Evaluation of analytical assays efficiency to detect aflatoxin M1 in milk from selected areas in Egypt and South Africa

Recently, methods to analyze aflatoxin M1 (AFM1) in milk and dairy products have been developed for both screening purposes (i.e., rapid, economical, and simple methods) and for confirmation by accurate, reproducible, and sensitive quantification. The aim of this study was to evaluate the efficiency of different rapid kits and techniques available on the market by using different analytical methods: thin layer chromatography (TLC), immunoaffinity column, AFM1 immunochromatographic strip, and ELISA; some samples were also submitted to HPLC for comparison of results. One hundred thirty-eight samples were collected from rural subsistence and commercial dairy farms in selected areas of Egypt and South Africa and analyzed for the presence of AFM1. The results obtained by AFM1 immunochromatographic strip indicated the lowest frequency of occurrence, with a detection incidence of 20.45% in Egyptian samples and 16% in South African samples. Aflatoxin M1 was detected by ELISA in 65 (73.9%) Egyptian milk samples, with a range of 8.52 to 78.06 ng/L, and in 34 (68%) South African milk samples, with a range of 5 to 120 ng/L. A higher incidence of AFM1 in Egyptian milk samples was shown by TLC (81.8%) compared with ELISA (73.9%). Samples analyzed by ELISA in South African milk samples demonstrated satisfactory correlation when compared with HPLC coupled with Coring cell (an electrochemical cell for the derivatization of AFM1). Among the positive samples, 18 of the Egyptian samples (20.45%) positive by ELISA had levels of AFM1 above the European Union (EU) regulatory limit (50 ng/L), whereas 65 samples (73.9%) were above the Egyptian regulatory limit (0 ng/L). Six of the South African samples (12%) tested by ELISA were above the South African (50 ng/L) and EU regulatory limits. The mean concentration of AFM1 was 25.79 ng/L in Egyptian samples and 17.06 ng/L by ELISA and 39 ng/L by HPLC in South African samples. These contamination levels would not represent a serious public health hazard according to EU legislation.