Interfacial Adsorption Characteristics And Stabilization Of Nanoparticles With Different Morphologies In Aqueous Two-phase Emulsion

Anaqueous two-phase emulsion with low interfacial tension and thick interfacial layer,was formed by mixing two thermodynamically incompatible hydrophilic macromolecules in a certain proportion.It has been reported that the emulsion system cannot be stabilized by surfactants,and the emulsion stabilization is mainly achieved by interfacial adsorption of solid particles and gelatinization of emulsions.This study aimed to explore the interfacial adsorption characteristics and stabilization ways of aqueous two-phase emulsion.The formation of the aqueous two-phase emulsion,and the adsorption characteristics and stability mechanism of solid particles at the water-water interface were revealed by investigating the adsorption of particles with different morphologies at the water-water interface and the gelatinization of emulsions.The results would provide innovative strategies for the structural design of food based on aqueous two-phase emulsion.The main results were as follows:(1)The effects of different morphologies and concentrations of solid particles on the microstructure,rheological properties and macroscopic stability of Pickering emulsion based on Pullulan polysaccharide/polyethylene glycol(PUL/PEG)were investigated.An aqueous two-phase emulsion system with PUL as the dispersed phase and PEG as the continuous phase was constructed,and the stability of PUL/PEG emulsion adsorbed by cellulose nanocrystals(CNC),whey protein isolate microfibers(WPIF)and whey protein isolate nanoparticles(WPIP)was compared.It was found that CNC could adsorb to the water-water interface to form a stable PUL/PEG Pickering emulsion compared with WPIF and WPIP,and the emulsion containing 0.2wt%CNC could be stored at room temperature for more than 7 days.The rheological analysis showed that the PUL/PEG emulsion stabilized by CNC exhibited elastic properties,and the increase of CNC concentration led to the enhancement of the network structure between droplets,which could improve the emulsion stability.(2)The adsorption behavior of particles at the PUL/PEG water-water interface was explored by measuring the contact angle,interface adsorption layer thickness,microrheology and the interfacial tension dynamics of CNC/WPIF/WPIP at the PUL-PEG interface.The results showed that the contact angle of CNC and WPIF in the PUL-PEG phases was greatly larger than that of WPIP,so CNC and WPIF could be adsorbed on the two-phase interface to form a clear interface layer.Additionally,the results of microrheological analysis indicated that CNC had the fastest diffusion rate at the interface,and could significantly increase the elasticity of the system.The interfacial tension of PUL-PEG was 0.74±0.085 mN/m by suspension drop method.(3)A layered gel based on WPIF/ASKP double aqueous emulsion was formed by taking advantage of the structural characteristics of WPIF-Fe2+/Fe3+complexation with Artemisia sphaerocephala Krasch polysaccharide(ASKP)-Fe3+.In the transition process of Fe2+to Fe3+,the WPIF and ASKP were crosslinked sequentially to achieve step-by-step cross-linking from inside to outside.The results indicated that WPIF would break under ultrasound action,forming short rod-like morphology.With the decrease of WPIF length,the formed gel microstructure gradually became dense and uniform,and presented a regular orientation arrangement.The WPIF obtained by ultrasound for 8 min significantly improved the gel strength,water holding capacity and viscoelasticity of the lamellar gel.