Effects of Enzyme Choice and Fractionation of Commercial Enzyme Preparations on Protein Recovery in Curd

Five different commercial milk clotting preparations (bovine rennet, calf rennet, calf rennet-porcine pepsin mixture, Mucor miebei protease, and modified Mucor miehei protease) were adjusted to equivalent milk clotting activities and then used to clot milk. Percentages of protein in the resulting wheys were compared. Calf rennet, bovine rennet, or modified Mucor miehei protease caused less loss of protein to the whey than Mucor miehei protease or calf rennet-porcine pepsin mixture. The five enzyme preparations were then fractionated by gel filtration. Fractions with milk clotting activity were pooled. Original enzyme preparations and the pooled fractions made from them were standardized to the same clotting activity, then used to coagulated milk to compare their effect on protein loss to the whey. Fractionation significantly improved protein recovery when bovine rennet and calf rennet-porcine pepsin mixture were used as coagulants but not when calf rennet, Mucor miehei protease, or modified Mucor miehei protease were used.