Study On The Effect Of Homogenization On Milk Fat Globule Membrane Protein Of Pasteurized Milk

The phenomenon of pasteurized milk fat floating occurs during storage which will affect the sensory quality and nutritional value.Homogenization can solve this problem effectively,and the effect of the homogenization process on the fat stability mainly depends on the change of the fat globule membrane protein.The aim of the present study was to examine the effects of homogenisation conditions(preheating temperature and pressure)on the pasteurized milk fat stability and milk fat globule membrane proteins,and to provide a theoretical basis for the production of pasteurized milk.The pasteurized milk with the best fat stability was screened out by measuring the stability index and the rate of fat floating.The homogenization process conditions were preheated the milk at 60 ? and the homogenization pressure was 40 MPa.At this condition,the surface mean diameter D32 of the milk fat globules was 0.387 ?m and the zeta potential was-11.3 mV.The extraction process of milk fat globule membrane protein was optimized based on the needs of this experiment,so that the extraction of fat globule membrane protein can achieve the best results under laboratory conditions.Concrete steps:The sample of milk was preheated to 36 ?,then the cream was separated by centrifugation at 4000 r/min for 20 min at 36 ? after addition of 28.6 g of sucrose 100 g-1 of milk.The top layer(cream)was collected.Cream was washed twice for 30 min at a 39 ? water bath for 30 minutes with slight turbulence in 5 weights of wash solutions centrifuged at 4000 r/min for 30 min at 25 ?.The top layer(cream)was the sample that contains fat globule membrane protein.The highest fat-stabilized milk fat membrane protein content was found by the.Kjeldahl method,and the casein micelle that loosely adsorbed on the membrane surface was the least.SDS-PAGE electrophoresis and LC-MS/MS techniques were used to investigate the changes of pasteurized milk fat membrane proteins treated with different homogenization processes:preheat temperature in the range of 50-70 ?,homogenization pressure in the range of 20-45 MPa,the homogenous pressure had no significant effect on the type of globule membrane protein of pasteurized milk.The preheating temperature had a significant effect on the type of globule membrane protein of pasteurized milk,but these differential proteins have no special molecular function by analyzing Gene Ontology,so the effect on fat stability of pasteurized milk depends on the content of main fat globule membrane protein and the change of binding mode.In homogenization pressure 20-40 MPa,preheating temperature 50 ?-70 ?,the contents of XO?BTN?ADPH?Lf??-lg??-CN??s2-CN were the lowest and the contents of MUC1??s1-CN??-CN?BSA were the highest when the preheating temperature is 60 ?.The contents of XO?PAS6/7?BTN?ADPH?FABP?Lf??-Lg were the lowest and the contents of BSA were the highest when the homogeneous pressure was 40 MPa.The fat globule membrane proteins-FABP,PAS6/7,MUC15 are thermally unstable.