Fate of aflatoxin M(1) during manufacture and storage of feta cheese.

The effect of feta cheese manufacture on aflatoxin M(1) (AFM(1)) content was studied using an enzyme immunoassay technique. Feta cheese was made from milk spiked with 1 and 2 microg AFM(1) per kilogram milk. Pasteurization at 63 degrees C for 30 min caused <10% destruction of AFM(1). During cheese making, the remaining AFM(1) in milk was partitioned between curd and whey with two-thirds retained in the curd and one-third going into the whey. Cheeses were then stored for 2 mo in 8%, 10%, and 12% brine solutions at 6 and 18 degrees C. There was a 22% to 27% reduction of AFM(1) during the first 10 d of storage, with slightly more loss as salt concentration increased and when the cheese was stored at 18 degrees C. Further storage caused only slight decrease in AFM(1) and after 30 d of brining there was no difference in AFM(1) content of the cheese based upon salt concentration of the brine. At 18 degrees C, no further losses of AFM(1) occurred after 30 d, and at 6 degrees C, there was continued slight decrease in AFM(1) levels until 50 d. After 60 d of brining, there was a total loss of 25% and 29% of the AFM(1) originally present for cheese brined at 6 and 18 degrees C, respectively. Thus, the combination of pasteurization, conversion of milk into feta cheese, and at least 50 d storage of cheese in brine caused a total loss of about 50% of the AFM(1) originally present in the raw milk.