Effects Of Instantaneous High-pressure On The Lipase And Lactoperoxidase In Raw Milk

Instantaneous high pressure is a high-tech developed in recent years,which have broad applicative prospects in the sterilization of liquid food and anti-enzymes.The effects of Instantaneous high-pressure on the lipase and lactoperoxidase in raw milk were investigated through single factor,multi-factor orthogonal and regression test(the processing pressure 0-140 MPa,the temperature 25-55℃,the processing time 0-10 min) in this paper,in order made high-pressure technology in food industry to reach industrialization.The test results show that:(1) The accuracy and reproducibility of the modified LP activity assay are satisfactory by 5-fold expansion of the reaction system,select the milk concentration of 40%,reaction 6 min at 26℃.(2) The sequence of three factors(the temperature A,the processing pressure B,the processing time C) affecting lipase's activity by instantaneous high pressure is as follows: B＞A＞C,and the pressure is the significant factor.The suitable conditions to inhibit its activity is:deal with the pressure of 100 MPa,the temperature of 55℃for processing 4 min.(3) The treatment of 40～80 MPa processing can significantly increased the activity of lactoperoxidase at 35℃for 4 min.At the same temperature,the activity decreased continuously within the range of processing time 2～8 min at 60 MPa(P＜0.05).The optimum temperature of the enzyme is about 45℃under the instantaneous pressure of 20 MPa.The sequence of three factors affecting the activity is as follows:the temperature A＞the processing pressure B＞the processing time C,and these factors have an interaction on the activity.The relationship between the activity Y and the three factors could also be demonstrated by a regression equation Y=62.69-9.43A~2-7.96B~2+3.44C~2.(4) There exist a high degree of correlative relationship between lipase's activity and milk acidity after processing by HP(The correlative coefficient is 0.860).