RELATIONSHIPS BETWEEN PLASMIN LEVELS IN RENNET CASEINS AND PROTEOLYTIC AND RHEOLOGICAL CHANGES ON STORAGE OF CHEESE ANALOGS MADE FROM THESECASEINS

Sixteen rennet casein samples and the corresponding sixteen cheese ana logues made from these caseins were obtained from a local processor. F ollowing storage at 4-degrees-C for 6 months, pH 4.6-soluble N content s of the cheese analogues increased, while alpha(s)- and beta-casein c ontents, elastic moduli and apparent relaxation times decreased. The b eta-casein and pH 4.6-soluble N contents of the 6 month old products w ere significantly correlated, both were significantly correlated with the plasmin (EC 3.4.21.7) contents of the corresponding rennet caseins from which the analogues were made and all three were significantly c orrelated with the rheological properties of the stored analogues. Of the compositional characteristics, only percent moisture in non-fat su bstance and percent fat in dry matter were significantly correlated (P < 0.05) with any of the proteolytic or rheological properties. The si xteen cheese analogues were also assayed at one time, when they ranged in age from 1 to 35 weeks, and highly significant interrelationships between plasmin activity, proteolysis and rheological properties were established. The results indicate that the plasmin content of rennet c aseins had a significant influence on the proteolytic and rheological changes that occurred during storage of cheese analogues made from the se caseins.