Stability of aflatoxin M 1 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 M 1 (AFM 1 ) and then were stored at 4°C for 2 weeks. Levels of AFM 1 in these dairy products were high, and then began to decrease during storage period at 4°C. Most of the AFM 1 (recoveries of 71%) appeared in yoghurt‐cheese after 14 days, this is due to AFM 1 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.