Proteolysis was assessed by determining water-soluble nitrogen (SN) and NPN content. The amount of NPN, expressed as a percentage of total nitrogen (TN; NPN/TN%), and SN/TN% were determined because they represent parameters to indicate the extent of proteolysis. For SN, 4 g of grated cheese was mixed with 20 mL of H2O at 40°C for 3 min. The homogenate was adjusted to a final volume of 100 mL and was left at 4°C for 12 h. Finally, it was filtered through Whatman no. 4 filter paper. For NPN, 10 g of grated cheese was mixed with 60 mL of H2O and 40 mL of 0.5 M sodium citrate. The homogenate was adjusted to a final volume of 200 mL. Ten milliliters of this solution was adjusted to a final volume of 50 mL with 15% TCA. Finally, it was filtered through Whatman no. 5 filter paper. The nitrogen contents of the filtrates and the TN were determined by the Kjeldahl method ( AOAC International, 2000; method 920.123).