Behavior of Aflatoxin M₁ During Manufacture and Storage of Queso Blanco and Bakers' Cheese

Queso Blanco and bakers's cheese were prepared from milk naturally contaminated with aflatoxin M₁ (AFM₁), and then were stored at 4°C and at -23 ± 6°C for 2 months. AFM₁ was found in both curd and whey. There was a 2.84-fold increase of AFM₁ in curd of Queso Blanco cheese over the amount present in milk from which the cheese was made. The AFM₁ content of the cheese varied during refrigerated and frozen storage, but AFM₁ was present near initial levels at the end of storage. Bakers' cheese was prepared with and without added rennet. More AFM₁ was found in cheese and whey than in milk from which cheese was made. AFM₁ tended to be concentrated in curd. Cheeses made without rennet had greater enrichment (4.24-fold increase over that found in milk) than those made with rennet (2.97-fold increase over that found in milk). The AFM₁ content in both types of cheese was variable but toxin remained in cheese through 1 month of refrigerated and 2 months of frozen storage.