| Due to chemical instability and solubility defects of bioactive substances,their bioavailability and efficacy are always reduced.Therefore,it is very important to develop the emulsion delivery system based on food grade colloidal particles.Pickering emulsions have attracted considerable scientific attention in recent years due to their comprehensive advantage in cost,quality and sustainability.Zein as a natural proline-rich protein,has the advantages of non-toxicity,good biocompatibility and biodegradation.However,it can not directly form a stable emulsion due to its high hydrophobicity.Thus,the wettability of zein is usually necessary to be modified.In this paper,zein-grape seed proanthocyanidin composite particles（ZPAPs）and zein-grape seed proanthocyanidin-pectin composite particles（ZPAAPs）were prepared by anti-solvent method and self-assembly method.The stability of binary and ternary nanoparticles and their differences were studied.Subsequently,ZPAPs and ZPAAPs were used as emulsifiers to prepare Pickering emulsions.The effects of different oil-water ratios,centrifugal force,p H and Na Cl concentration on the stability of the emulsion were studied.Finally,the curcumin was used as loaded substance,and the effects and difference of storage stability and digestion stability of curcumin were studied with binary and ternary emulsion laoding.The main research contents and results are as follows:（1）Construction and characterization of ZPAPs and ZPAAPs.The ZPAPs and ZPAAPs were prepared using anti-solvent method and self-assembly method.The results of three-phase contact angle showed that both ZPAPs and ZPAAPs significantly reduced the hydrophobicity of zein,and three-phase contact angle of ZPAAPs was 93.26±0.8°,which was conductive to emulsion stability.FTIR showed that hydrophobic interaction,hydrogen bond and electrostatic interaction were the main driving forces for the formation of composite nanoparticles.DSC results showed that the addition of proanthocyanidins and pectin significantly improved thermal stability of zein.（2）The effects of different conditions on ZPAPs stabilized Pickering emulsions（ZPAPEs）and ZPAAPs stabilized Pickering emulsions（ZPAAPEs）.The effects of different oil-water ratio,centrifugal force,p H value and Na Cl concentration on the stability,droplet morphology and emulsification index of emulsion were measured,and the rheological properties of the emulsion were also studied.There was no obvious phase separation for ZPAPEs and ZPAAPEs with oil phase fraction in the range of 0.5-0.7,even after a 30-day storage.The emulsion gels of ZPAPEs and ZPAAPEs were formed in the range of φ=0.5-0.7 and φ=0.4-0.7,respectively,indicating that they have good stability.Ternary emulsion had better centrifugal stability,Na Cl stability and p H value stability than binary emulsion.Confocal laser scanning microscope（CLSM）showed that particles had stably anchored on the oil-water interface which could effectively prevent droplet aggregation.The rheological results revealed that the emulsion had good viscoelasticity and plasticity.（3）The characterization and antioxidant capacity of curcumin-loaded emulsion.The curcumin-loaded emulsion showed orange appearance.Microscope and particle size results showed that the micromorphology and particle size of the emulsion were not changed by the loading of curcumin.The rheological results showed that the emulsions loaded with curcumin still had elastic gel network structure,and the difference between storage modulus and loss modulus increased further,indicating that the emulsions became more rigid.The emulsion had strong DPPH and ABTS radical scavenging activities before loading,after loading curcumin,DPPH radical scavenging activities of ZPAPEs and ZPAAPEs increased to 82.9% and 89.4%,respectively,and ABTS radical scavenging activities were increased to 84.1% and 86.3%,respectively.（4）In vitro digestion and storage stability of Pickering emulsion loaded with curcumin.Curcumin directly dissolved in peanut oil was the control group,and the content of curcumin in emulsion system decreased slowly.The time required for 50% degradation of the curcumin（half-life）in ZPAPEs was about 266 h and ZPAAPEs still contained 54.4% curcumin after storage for 15 d,while the half-life of the control group was about 79 h.Meanwhile,emulsion encapsulation significantly improved the digestive stability and bioavailability of curcumin.The bioavailability of ZPAAPEs and ZPAPEs were 39.7% and 33%,respectively,and the digestive stability was 78.46% and 71.8%,respectively.In conclusion,ZPAAPs had nearly neutral wettability and stronger thermal stability.ZPAAPEs was more resistant to changes in centrifugal force,p H and salt ion concentration.In curcumin loading experiments,ZPAAPEs could effectively reduce the degradation of curcumin,significantly improve the bioavailability and digestive stability of curcumin,which showed a stronger protective effect. |
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