Preparation,Characterization Of Zein-Based Composite Particles With High Physical Stability And Its Application In Yogurt

In recent years,curcumin had drawn close attention because of its unique bioactivity and function,but its utilization is limited due to its low water solubility and bioavailability.Nanoparticles were effective carriers to improve the solubility,stability and bioavailability of curcumin.The composite particles composed of zein and polysaccharides were ideal carriers of curcumin,but these composite particles were prone to physical instability due to the influence of microenvironment,which is characterized by easy aggregation,precipitation and difficult dispersion between carrier particles,which affects the biological accessibility of curcumin.Therefore,it was an urgent problem to realize the steady-state of zeinpolysaccharide composite particles.In this study,zein-arabic gum composite particles were prepared by anti-solvent precipitation method with zein as the substrate,and its instability mechanism was revealed.Additionally,zein-gum arabic-tannic acid ternary composite particles(TCPs)with different structures were constructed,and the formation mechanism and steady-state mechanism of ternary composite particles were revealed.The effects of ternary composite particles with different structures on the embedding rate and drug loading capacity of curcumin and the formation mechanism were clarified.The effects of curcuminloaded TCPs of different particle sizes on the antioxidant capacity and bioavailability under in vitro conditions were studied.The effects of adding curcumin nanoparticles on the physical properties of yogurt was studied.The main results were as follows:(1)By measuring the diameter,electric load and microstructure of the particles,it was found that zein and gum arabic could form composite particles with "core-shell structure".The effects of different dissociating agents(Na Cl,sodium dodecyl sulfate,urea,etc.)on the stability of the composite particles were evaluated,and the instability mechanism of zeingum arabic composite nanoparticles was revealed.When the mass ratio of zein to gum arabic was 3:1～1:3,the hydration diameter of the composite nanoparticles was in the range of 173.9±5.8～199.4±13.4 nm,which increased compared with the single zein particles,and the addition of gum arabic changed the surface charge of the particles from positive to negative.It was found that low concentration of sodium chloride(50 mmol/L)and sodium dodecyl sulfate(0.05%)would destroy the structure of zein-gum arabic composite particles and change the particle diameter and structure,but the urea of 0～8.0 mol/L solution had no effect on the particle diameter,indicating that the stability of zein-gum arabic composite particles was mainly maintained by electrostatic and hydrophobic effects.When tannic acid was added,the stability of zein-gum arabic composite particles was significantly improved,and the resulting zein-gum arabic-tannic acid TCPs did not aggregate or precipitate under the conditions of different concentrations of Na Cl(0～3.0 mol/L)and different pH values(4.0,7.0 or 9.0),and their hydration diameter was between 125.5±16.2～291.6±15.2 nm.(2)By adjusting zein concentration,core-shell ratio,ethanol concentration,temperature,p H value and salt ion conditions,the diameter and structure of ternary composite particles were regulated,and the formation mechanism of ternary composite particles was revealed.The concentration of zein had the greatest effect on the hydration diameter of ternary composite particles,and the hydration diameter of the particles was 94.3±0.6～300.9±6.6 nm.When the core-shell ratio is 3:1～1:3,the particle size range is 114.5±0.4～127.3±0.4 nm;After heat treatment at 40 ℃,the hydration diameter of the particles increased to 227.8±1.3nm;The hydration diameter of TCPs decreased from 250.0±4.5 nm to 107.7±1.3 nm when the ethanol concentration was in the range of 60%～90%.Using fourier transform infrared spectroscopy,nuclear magnetic resonance hydrogen spectrum and fluorescence spectrum methods analysis found that,compared with the zein-gum arabic composite particles,the introduction of tannic acid have no effect on the electrostatic interactions between the composite particles,but obviously enhances the hydrogen bonding interaction between the ternary composite particles,the TCPs is resistant to salt and alkali.(3)By adjusting the concentration of zein and the mass ratio of zein to gum arabic,the structure of curcumin loaded TCPs was adjusted,and the effects of ternary composite particles with different structures on the embedding rate and drug loading capacity of curcumin and the particle formation mechanism were clarified.When zein concentration was 0.1%～2.0%,the hydration diameter of curcumin loaded TCPs ranged from 124.7±0.4～210.5±1.5 nm,and the maximum embedding rate and drug loading capacity of curcumin were 95.8% and 1.48%,respectively.When the mass ratio of zein to curcumin was 100:1～2:1,the particle hydration diameter ranged from 112.1±0.9～142.3±1.5 nm.The maximum embedding rate and drug loading capacity of curcumin were 96.6% and 4.38%,respectively.By means of fourier transform infrared spectroscopy,fluorescence spectroscopy and X-ray diffraction spectroscopy,it is found that curcumin can bind to zein through hydrogen bonding,and gum arabic,tannic acid and curcumin can quench the fluorescence signal of zein,among which tannic acid had the strongest fluorescence quenching effect on zein,after curcumin was embedded in ternary composite particles,its structure changed from crystalline state to amorphous state.(4)The stability,antioxidation and bioavailability of curcumin loaded composite particles were compared.It was found that the curcumin loaded TCPs had stronger physical stability and storage stability than the control group of zein-curcumin and zein-gum arabiccurcumin composite particles,The stability of curcumin loaded TCPs with different sizes was related to their particle size and tannic acid content.Curcumin loaded on TCPs had good light stability and thermal stability.At 45,65 and 85 ℃,the maximum retention rates of curcumin were 98.8%,97.67% and 94.3% respectively.The longest half-life of curcumin loaded on ternary composite particles was 2312±77 min,which was 2.9 times that of free curcumin.The bioavailability and antioxidation of curcumin loaded on TCPs were significantly higher than those in the control group.The bioavailability of curcumin was up to 37.6%,which was 8.97 times higher than that of free curcumin.The water holding capacity of curcumin nanoparticle yoghurt was similar to that of the control group,and the hardness and elastic modulus of curcumin nanoparticle yoghurt were higher than those of the control group.When the content of composite particles was 10%,the hardness of yoghurt was 0.51N,indicating that curcumin nanoparticles were promising to be utilized in yoghurt industry.In summary,this study achieved the controllable preparation of zein-gum arabic-tannic acid composite nanoparticles with acid and alkali resistance and salt tolerance,and clarified the effects of composite nanoparticles with different structures on the encapsulation rate and drug load of curcumin and the particle formation mechanism.The results of this study have certain reference significance for the application of hydrophobic biologically active substances in food matrices,and provide theoretical and scientific basis for the development and application of zein-based composite nanoparticle in functional foods or as food ingredients.