Effect Of Dynamic Ultra-High Pressure Homogenization On Enzymatic Hydrolysis Characteristics Of Casein

Dynamic high pressure homogenization as a novel physical treatment method,is widely used in the processing and preservation of dairy products,meat,beverages,fruit juice and so on.Ultra-high pressuree homogenization(UHPH)can kill food-borne microorganisms and increase stability of food to achieve effects of homogenization,emulsification and improvement of food appearance.At the same time UHPH can also change the structure and function of large molecules to increase the application value when acts on large molecules.Our country has rich resources of casein,which is a kind of complete proteins and has high nutritional value,but is difficult to be digested by body after eating.Moreover,as the functionality of the casein is poor,the development of casein is relatively slow in the food field.It is shown that the dynamic high pressure homogenization can destroy the structure of the protein and improve the functionality of the protein and the enzymatic characteristics.However,the application of dynamic high pressure homogenization in improvement of the solution of casein is less.This topic takes casein as the research object and firstly uses dynamic ultrahigh pressure carries on the processing of epicuticular casein to destruct micelle structure of the casein,to research systematically dynamic ultrahigh pressure effect on conformation and function of the casein and analysis effects of dynamic ultrahigh pressure homogeneous treatment on hydrolysis degree of casein,the kinds of hydrolysate amino acids and antioxidant activity of the production,to discuss inner link of internal structure zymohydrolysis characteristic of casein.The obtained results will be helpful to provide important basises for developing the dynamic ultrahigh pressure processing technology of food and to provide a theoretical basis for the preparation of bioactive peptides,flavor peptides and other new products.The main contents and results of this study as follows:1.Effect of dynamic high pressure homogenization on the structure and functionality of caseinThe solution of casein was treated with dynamic UHPH in this study to research the effects of different stress level on structure casein(Sulfhydryl Group and Disulfide Bonds,surface hydrophobicity and secondary structure content)and functional properties(average particle size,solubility,foaming,emulsification,Zeta potential,the emulsion particle size).The results showed that the homogenization dynamic ultrahigh pressure can damage the structure of the casein,leading to the average particle size,Sulfhydryl Group and Disulfide Bonds and surface hydrophobicity and secondary structure corresponding changes.Moreover,functional properties of casein protein(solubility,foaming,emulsification)were improved in much degreee.Through the study known,solubility,foaming and emulsification function of casein were also improved when 150 Mpa treatment,150 Mpa as reference index of the subsequent experiment.2.Optimization of casein hydrolysis conditionsCasein solution after 150 Mpa treatment was enzymed by papain,the degree of hydrolysis as measurement index,enzyme dosage,temperature and time of enzymatic hydrolysis as effect factors of single factor experiment;on basis of the results,the optimization method of enzymatic hydrolysis conditions for the optimization of response surface interaction to determine the optimal conditions for enzymatic hydrolysis,enzyme dosage of 5mg/mL,temperature of 45?,the reaction time of 3 h.The degree of hydrolysis was 55%.3.Effect of dynamic high pressure homogenization on the hydrolysis of caseinThe casein after 150 Mpa treatment was enzymated by using the optimal enzymatic hydrolysis conditions of experiment 2,without dynamic ultrahigh pressure homogeneous processing casein as controls.The hydrolysis degree,solid content,amino acid and free amino acid composition,molecular weight distribution,DPPH scavenging rate and cell antioxidant activity were determined.The results showed that the dynamic high-pressure treatment can greatly improve the degree of hydrolysis,solids content,casein and the DPPH removal rate and cell antioxidant composition.Moreover,it was also shown that through the analysis of hydrolysis products of amino acids and free amino acids,microfluidization treatment can not only improve the content of total amino acid content,but also every kind of essential amino acids are the control group improved.From the results we can know that the function of dynamic high-pressure treatment not only can change the structure and improve the casein,casein,but also affect the enzymatic characteristics,indicating that the enzyme structure characteristics of casein was related with its structure characteristics.