The advantages of irradiation is that it is easy and safe and does not leave residual molecules in the final product as when chemical inactivation methods are used. Today γ irradition is mandatory in Europe for fetal bovine serum. Validation experiments of the γ irradiation (dose: 25-35 kGy) of porcine pancreatic trypsin powder indicated a 6.7 log 10 reduction of the median tissue culture infective dose (TCID 50 ) (Erickson et al., 1989) .