Fate of aflatoxin M1 during production and storage of parmesan cheese

The fate of AFM1 during production of a long maturing cheese (Parmesan cheese) was assessed. Different levels of AFM1 contamination and of the fat/casein (F/C) ratio of milk were considered, in order to evaluate if these factors can influence the enrichment factor (EF) of AFM1 in cheese. For this purpose, 24 cheese-makings were carried out using naturally contaminated milk at 3 different AFM1 levels and at 2 F/ C ratios. AFM1 analysis was performed by HPLC in raw milk, cream, cauldron milk, liquid cattle rennet, whey, curd and cheese at 3, 9, 16 and 24 months of ageing. The mass balances of the cheese-making processes were close to 100%; in whey, AFM1 concentration was about 40% less than the concentration in cauldron milk. The EF in curd was between 4.0 and 5.2, with an average value of 4.7 ± 0.4; this factor was not significantly affected by either AFM1 contamination level or F/C ratio. During maturation, AFM1 concentration and consequently EF increased from curd to 16 ageing months; successively, AFM1 slightly decreased at 24 months and consequently the EF. At 3, 9, 16 months of maturation, the EF was significantly higher for cheeses prepared using milk with low F/C than those with high F/C milk; on the contrary, EF was not significantly influenced by the AFM1 contamination level. In cheeses, EF values were between 4.7 and 6.3; from these results, the maximum admissible level for AFM1 in Parmesan cheese should be about 0.275 mg kg1.