Fate of aflatoxin M1 during manufacture and storage of yoghurt

Aflatoxin M-1 (AFM(1)) is an important mycotoxin frequently found in milk and dairy products. Yoghurt from cow's milk artificially contaminated with AFM(1) at level of 100 ng/L (ppt) was fermented to reach pH 5.1 +/- 0.04. The samples were stored at 4 degrees C for up to 3 weeks. Analysis of AFM(1) in yoghurt samples was carried out using solid phase extraction coupled with competitive enzyme-linked immunosorbent assay (ELISA) method. AFM(1) in yoghurt showed a significant increase (P<0.01) compared with those initially added to milk. The level of AFM(1) in yoghurt samples were 2.1 +/- 0.07 fold. During the refrigerated storage AFM(1) was rather more stable, the percentage losses were zero, 3.75 +/- 0.05, 6.25 +/- 0.16 and 13.75 +/- 0.24 by the end of storage with pH 4.9 +/- 0.08, 4.5 +/- 0.01, 4.1 +/- 0.03 and 3.9 +/- 0.0, respectively. Changes in AFM(1) content of yoghurt samples were statistically insignificant (P>0.01) during 3 weeks storage. The results indicate that the necessary precaution has to be taken to minimize the AFM(1) contamination in milk.