| Zein is the main storage protein in corn and is a major by-product of the deep-processing of corn.In addition to the advantages of low economic cost,easy extraction,low allergenicity and good biocompatibility,zein enjoys self-assembly properties and unique solubility,which can be used to build stable bio-delivery systems.Pickering emulsion is stabilized by solid particles and acts as effective carriers for fat-soluble bioactive compounds,enhancing their stability and bioaccessibility.In this study,covalent nanoparticles were prepared by zein and adzuki bean seed coat polyphenol（ABSCP）and stabilized Pickering emulsion.Furthermore,the Pickering emulsion was then used to deliver astaxanthin.The main findings are as follows:（1）Covalent nanoparticles（ZAP0-ZAP4）were formed by 2%（m/v）zein and 0,0.01,0.02and 0.04%（m/v）ABSCP,respectively,under alkali treatment method.With increasing ABSCP concentration,the average particle size of the nanoparticles gradually decreased from 197.2 nm（ZAP0）to 175.97 nm（ZAP4）,and the absolute value of the-potential increased from 41.33 m V（ZAP0）to 48.85 m V（ZAP4）.The redshift of the amide II band of the FTIR spectra occurred(about 10 cm-1),and the increase in the intensity of the characteristic absorption peaks of the UV spectrum as well as the decrease in the fluorescence intensity,demonstrates that ABSCP addition altered the secondary and tertiary structure of zein.The X-ray diffraction peaks of the ZAP were wide and gentle,indicating that the nanoparticles belong to a non-crystalline amorphous structure.In addition,the antioxidant activity and thermal stability were enhanced with the increase in ABSCP concentration,and the surface hydrophobicity decreased significantly.（2）Pickering emulsion（ZAE0-ZAE4）was prepared by high-speed shearing,using 90%（v/v）of ZAP as the aqueous phase,and 10%（v/v）of corn oil as the oil phase.The test results show that the ZAE are stable in their apparent state and belong to O/W type emulsions.The rheological tests prove that the emulsions are non-Newtonian fluids.After 21 days storage,the mean particle size of ZAE1-ZAE4 did not increase significantly and the red-yellow color of the emulsions was still retained.Besides,as the concentration of ABSCP increased,the flocculation of the emulsion gradually weakened,ZAE4 with a 26.99%decrease in the creaming index compared to ZAE0（control）,demonstrating the strong storage stability of the emulsion stabilized by covalent composite nanoparticles.At the same accelerated oxidation time,the amount of primary and secondary oxidation products produced by the emulsion decreases with increasing ABSCP concentration,demonstrating that the emulsion has oxidative stability.Furthermore,ABSCP addition was effective in reducing the production of free fatty acids（FFA）,with the final FFA release rate decreasing from 31.09%（ZAE0）to 26.20%（ZAE4）.In general,the Pickering emulsion（ZAE4）stabilized by ZAP4 showed the best overall properties.（3）ZAP4 were selected to stabilize the astaxanthin-loaded Pickering emulsions（ZAE4-A）,and emulsions prepared by zein without ABSCP added（ZAE0-A）were used as control for the analysis of physicochemical stability and digestion characteristics.The experimental results showed that ZAE4-A exhibited stronger physical stability and a higher retention rate of astaxanthin than ZAE0-A under different ionic strength treatment,thermal treatment and UV irradiation.In vitro simulated gastrointestinal digestion tests indicated that ZAE4-A and ZAE0-A presented an increasing trend in average particle size during digestion,with flocculation occurring under gastric conditions and flocculation diminishing in the intestinal phase,although the large granular matter was still present.In the gastric phase,the release of astaxanthin was below 15%,with the final release of 44.34%and 41.44%of astaxanthin from ZAE4-A and ZAE0-A,respectively.In addition,the bioaccessibility of astaxanthin could reach 55.66%in the ZAE4-A system,a significant increase compared to the astaxanthin free in the oil phase（Oil-Ast）. |
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