Study On Aggregation Behavior Of Zein And Preparation And Application Of Its Composite Nanoparticles

Nanoparticles are widely used for carriers of active substances and stabilizers for emulsions.Zein is an excellent substrate for nano-delivery carriers and widely used in food and medicine fields due to its safety,self-assembly,good biocompatibility and biodegradability.Understanding the aggregation behavior and self-assembly mechanism of zein in solvents is of great significance for the preparation of nanoparticles and their application in emulsion systems.In this paper,zein was used as the main substrate,and DLS,fluorescence spectrum,SEM,FTIR,DSC,CLSM and interface contact angle were used to explore its aggregation behavior and self-assembly mechanism in different polar solvents.Zein/SSOS composite nanoparticles(ZSPs)were prepared by anti-solvent precipitation method.The effects of alcohol solvents,ultrasonic treatment and SSOS concentrations on particle sizes,surface hydrophobicity,protein secondary structure,interfacial properties and thermal stability of ZSPs were studied.At the same time,ZSAPs composite colloidal particles were formed by loading anthocyanins on ZSPs particles,which were applied to the preparation and research of Pickering emulsion.The effects of protein concentrations and oil phase volume fractions on the stability,oxidation resistance and interface structure of ZSAPs Pickering emulsion were explored.The main research results are as follows:(1)Study on the aggregation behavior of zein.Hydrogen bond,disulfide bond and hydrophobic interaction of zein were formed in the solvent.The different solvent polarity and concentration caused the change of protein particle size,surface hydrophobicity and spatial conformation.Zein dissolved in 100% acetic acid and 80% ethanol and isopropanol solution had a good dissolved state and high light transmittance.SEM results showed that zein was induced by solvent to aggregate and self-assemble into spherical particles.The contact angles of zein protein dissolved by 80% acetic acid and ethanol on the hydrophobic side were 88.90° and 86.60°,showing neutral wettability.The air side contact Angle of protein film formed from methanol solution was the largest,which was 72.10°.(2)Preparation and characterization of ZSPs.Stable ZSPs nanoparticles were formed by adsorption of SSOS on the surface of zein through hydrogen bonding and hydrophobic interaction.Solvent and ultrasonic time affected the folding and unfolding of hydrophobic long chains.When the ultrasonic time was more than 20 min and the concentration of SSOS was greater than 4%(w/v),the stability of ZSPs particles decreased and protein tended to aggregate into macroscopic particles.The change of solvent polarity and the driving force of self-assembly caused the transformation of the secondary structure from?-helix to ?-folded conformation.DSC analysis showed that the thermal stability of ZSPs was improved by ultrasonic treatment with ethanol for 10 min,and the Tg of ZSPs reached153.6 ?.(3)Preparation of ZSAPs and its application in Pickering emulsion.The loading of anthocyanin could improve the antioxidant activity and stability of Pickering emulsion.When the complex ratio of zein to SSOS was 0.5,ZSAPs particles showed higher stability and emulsifying activity.ZSAPs particles could stabilize Pickering emulsion with oil phase volume of 50%,and improve the interfacial stability and emulsified total activity of the emulsion.This study provided reference for the construction of delivery system with zein as bioactive substance and antioxidant Pickering emulsion system.