Stability of aflatoxin M1 during manufacture and storage of yoghurt, yoghurt‐cheese and acidified milk

Yoghurt, yoghurt‐cheese and acidified milk were prepared from pasteurised half‐cream milk, naturally contaminated with aflatoxin M1 (AFM1) and then were stored at 4°C for 2 weeks. Levels of AFM1 in these dairy products were high, and then began to decrease during storage period at 4°C. Most of the AFM1 (recoveries of 71%) appeared in yoghurt‐cheese after 14 days, this is due to AFM1 being associated with casein fraction. Whereas pH values of yoghurt‐cheese during refrigerator storage ranged from 5.15 to 4.65 and titratable acidity ranged from 3.9 to 3.5 g lactic acid litre−1, whilst AFM, (recoveries of 41%) from yoghurt after manufacture and storage was much more susceptible to reduction by storage this is due to the higher acidity (range 2.3–3.1 g litre−1) of yoghurt by the action of microorganisms, besides the changes in pH values (5.10–4.70). When acidified milk was used the recoveries of toxin were 34.2% after 2 weeks; pH values ranged from 2.95 to 2.85 and titratable acidity ranged from 2.3 to 2.2 g litre−1 during storage.