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.