The Effect Of Ultra High Pressure Treatment On Activities Of Plasmin And Lipase In Bovine Milk

In our project we have studied the varying regulation activities of plasmin and lipase in bovine milk, under treatment condition from 40MPa to 900Mpa, different temperature, time, and pressure exerting' ways. Within pressure treatments at 40MPa to 80MPa, the activities of plasmin and lipase were increasing. However, there was pressure treatment no significant effect (P>0.05) on increasing activities. Under treatment condition from 500MPa to 900MPa, activities of both enzymes were completely inactivated by treatment parameters of 900MPa for 4min at ambient temperature. Treatment condition within pressure value from 350MPa to 850MPa, the lowest pressure for inactivating plasmin and lipase were 450-500MPa, alkaline phosphatase was 550MPa-650MPa, the highest pressure for inactivating lipase was 750MPa, for plasmin 850MPa, and alkaline phosphatase above 850MPa. Pressure treatment had an extreme significant effect (P<0.01) on inactivating these enzymes. However pressure retention time and pressure exerting ways no significant effect (P>0.05). Among the pressure exerting ways, the oscillatory and pulsed treatment were more effective than other pressure exerting ways on inactivating enzymes. The optimum processing conditions for inactivation of plasmin was 850MPa, pressure retention time 4min, and pressure exerting ways of oscillatory and pulsed treatment, for lipase being 750MPa, 8min ,and oscillatory and pulsed treatment ,and for alkaline phosphatase 850MPa, 8min ,and oscillatory and pulsed treatment too. UHT treatment can completely inactivate plasmin and lipase as well as the high pressure treatment. However comparing with high pressure treatment, UHT treatment induced more denaturation of whey protein of milk.