STUDIES ON PROTEOLYTIC DEGRADATION OF CAS EINS .2. INFLUENCE OF PLASMIN ON THE PROTEOLYSIS IN GOUDA CHEESE

The influence of plasmin on the specificity of proteolysis in Gouda ch eese was investigated after the addition of (a) plasmin (10 U/100 I ch eese milk), (b) plasminogen and urokinase (an 10 U/100 I cheese milk) and (c) 6-aminohexanoic acid (400 g/100 I cheese milk) in 5 (experimen t A, B) and 2 (experiment C) repetitions of the 3 experimental product ions and 10 repetitions of the control productions. In the experimenta l cheese samples (a) and (b) the plasmin activity was 2,5 times higher than in the control productions. After 24 weeks of cheese ripening el ectrophoretic analysis of the cheese and the determination of the a-am ino-groups showed a 15% higher proteolysis in the experimental product ions (a) and (b). The three-way principal components analysis of the c omplex data array resulting from RP-HPLC analysis of the water-soluble peptides (molecular mass <5000) of cheese revealed, that the enzymic factor can be identified as the second principal variance in addition to the time dependend variabilities of the peptide profiles of the che ese. Up to 4 weeks of ripening the greatest dynamic changes of degrada tion of casein were detectable. During 4 to 12 weeks of ripening only few differences still arose between the samples, and from 12 to 24 wee ks of ripening a constant level of the determined variabilities existe d. Sensoric analysis proved the same good quality of the plasmin treat ed cheese samples compared to control productions. Bitterness was not detected in any of the cheeses.