Abstract: Plasmin is the main endogenous enzyme in milk. Plasmin, plasminogen, plasminogen activator, plasminogen activator inhibitor and plasminogen inhibitor constitute plasmin system. Any factors that activate plasminogen can increase plasmin activity, and thus affect the quality of dairy products, such as gelation, bitterness of UHT milk, cheese curing and flavor changes etc. Apart from heat treatment, high pressure processing and exogenous enzyme can change plasmin system, and thus affect quality of milk products. Research on kinetic changes of plasmin system can provide the theoretical basis for denaturation of plamin, as well as provide the kinetic parameters for research on quality changes of milk products.

Key words: plasmin, plasminogen, kinetic equation, quality of milk products