Fate of Aflatoxin M₁ in Brick and Limburger-like Cheese

Three batches of brick cheese were prepared, using milk which was naturally contaminated with aflatoxin M₁ (AFM₁). Cheeses were allowed to ripen with a smear for 2, 3 or 4 weeks, and then were either waxed or wrapped in foil to simulate production of mild brick, aged brick or Limburger-like cheese, respectively. These cheeses were analyzed for AFM₁ at intervals for about 26 weeks. There was an average 1.7-fold enrichment of toxin in the curd over that in milk. Levels of AFM₁ in cheese started low, appeared to increase at about 4 weeks of age and then dropped to initial levels in cheese ripened with a smear for 3 or 4 weeks. At no time did amounts of AFM₁ drop below initial levels. Toxin concentrations appeared to increase most in the rind of cheeses ripened with a smear for 2 or 3 weeks. When such ripening was for 4 weeks, levels of AFM₁ in the rind decreased, whereas levels in the center of the brick remained constant or increased.