Fabrication And Characterization Of Hollow Particles Of Zein And Whey Protein And Their Stabilized Emulsions

Compared with solid particles,hollow particles have the advantages of high surface area,low density,high loading amount and sustained release,which have attracted more and more attentions in related fields such as biology,energy,environment.Compared with inorganic hollow particles,protein-based hollow particles are widely used in the food field due to their biodegradability and biocompatibility.Zein is the main storage protein in corn,zein hollow particles can be prepared by using anti-solvent precipitation method with inorganic salts as the sacrifice template.However,due to zein contains more than 50% hydrophobic amino acids and its isoelectric point p H is about 6,the stability and dispersibility of zein hollow particles are poor in neutral conditions.At present,relevant researchs mainly focuses on the introduction of polysaccharide or water-soluble proteins coating in the form of non-covalent binding to improve the water dispersibility and physical stability of zein hollow particles,while the research on the stabilization of zein hollow particles by covalent binding and complex proteins is lacking.Compared with surfactant as emulsifier,Pickering emulsions stabilized with solid particles have better stability,at present,the research about zein-based hollow particles as the emulsifier of Pickering emulsion has not been reported.Therefore,in this studty,zein-WPI hollow particles were prepared with alkaline heated treatment combined with antisolvent precipitation method,and zein-WPI hollow particles were used for the embedding and loading of curcumin.In addition,emulsions stabilized with zein-WPI hollow particles were prepared,and the structure of hollow particles at the oil-water interface was characterized.The main contents and results of this study are as follows:1.Formation and characterization of zein-WPI hollow particles.Alkaline heated treatment combined with antisolvent precipitation method were developed to fabricate the hollow particles with a mixed shell of zein and WPI.At neutral condition,0.25% WPI was enough to stabilize complex protein hollow particles containing 0.5% zein.At p H 7,a greater portion of proteins participate the formation of hollow particles than p H 11,and proteins stack more tightly in the shell.The diameter of zein-WPI hollow particles was about 90 nm at p H 11 and about 198 nm at p H 7.Both non-covalent and covalent interactions are involved in the formation of zeinWPI hollow particles,among non-covalent interactions,hydrophobic interactions play a dominant role,while hydrogen bonding and electrostatic interactions play a secondary role.Cys,Tyr and Lys participated in the covalent interaction to form hollow particles,and disulfide bonds play an important role in the formation of the shell.In addition,zein-WPI hollow particles have good storage stability,at p H 7,there is no significant change in particle size and ζ-potential after storage at 45℃ for 14 days.Zein-WPI hollow particles can be used for the embedding and loading of curcumin at neutral condition,when the ratio of zein and curcumin was 1:0.1 and1:0.2 the encapsulation efficiency of curcumin were respectively 88% and 81%,the loading capacity were respectively 6.20% and 11.40%.2.Preparation and characterization of emulsions stabilized with zein-WPI hollow particles.The three-phase contact angle of zein-WPI hollow particles at p H 7 in MCT was 92°,which was close to middle wettability.In the process of preparing emulsions stabilized with zein-WPI hollow particles by shearing,the structure of hollow particles was not destroyed.Increasing the concentration of zein-WPI hollow particles or increasing the mass fraction of oil phase can weaken the phase separation of emulsions,and the effect of increasing the mass fraction of oil phase is remarkable.When the concentration of zein-WPI hollow particles was 4% and the mass fraction of oil phase was 10%,the average particle size of emulsions was the smallest,about 18 μm,and the emulsion type was O/W.With the phase separation of the emulsions,the oil content of upper emulsion was increased,the average particle size was large,the emulsion droplets were close to each other and tightly distributed,zein-WPI hollow particles existed at the oil-water interface in the form of single particles and aggregates,and the surface coverage was low.At lower emulsion,the average particle size was smaller,the emulsion droplets were dispersed in the aqueous phase,zein-WPI hollow particles mainly existed at the oil-water interface in the form of single particles,and the surface coverage was high.