Construction And Application Of Zein/polysaccharide Complex Coacervation Embedding System

Complex Coacervation has many advantages,such as simple operation,high encapsulation efficiency,pH responsibility,controllable release,etc.,and has been a research hotspot in the interaction between protein and polysaccharide.Up to now,there are few systematic studies on the complex coacervation between protein nanoparticles(NPs)and polysaccharides.In this paper,Zein(Z)was firstly used to prepare Zein nanoparticles(ZNPs)with hydrophobic core by anti-solvent method,and then complex coacervates with hierarchical structure were constructed by spontaneous reaction between the ZNPs and water-soluble chitosan(CS),and the coacervated Pickering emulsion were further fabricated by emulsification method.Active substances(curcumin,quercetin,probiotic and rutin)were successively loaded into each hierarchical structure(particle,coacervate,oil phase and interface)of the above-mentioned constructed system.The formation mechanism and stability regulation as well as the protection mechanism of the hierarchical system for delivering active substances were studied.The in-depth study of this aspect is helpful to reveal the characteristics and advantages of hierarchical particles and coacervated Pickering emulsion as bioavailability-improved carrier for active ingredients.Moreover,it has important guiding significance to promote the construction of new food composite carrier.The main research results of this paper are presented as follows:(1)In this paper,based on the anti-solvent and complex coacervation method,Zein and CS were successfully used to prepare the particles with hierarchical structure(hierarchical particles for short),and the co-encapsulation of curcumin and quercetin with different polarity was achieved.The results showed that pH,polyphenol type and polyphenol-polyphenol ratio had significant effects on the formation of the complexes.By regulating the degree of interaction between Zein nanoparticles and CS by pH,the nanometer complexes at a wide pH range(3.0-6.5)and micron coacervate at pH 7.0can be obtained.Curcumin and quercetin with different polarity had different location distribution in the hierarchical structure.Hierarchical particles possessed good storage stability and provided effective protection for curcumin and quercetin,with high embedding rate(> 95%)and certain sustained release effect.(2)In this paper,based on the anti-solvent and complex coacervation method,zein-CS was used to construct the complex coacervates with hierarchical structure(hierarchical coacervates for short),and the co-delivery of polyphenol and probiotic was realized.Firstly,the results showed that the37 ℃,pH 7.0 and 1% were chose as the optimal culture temperature,pH,inoculation amount and culture time for the Lactobacillus casei(L)according to the absorbance and pH.Subsequently,the formation mechanism of hierarchical coacervates loaded with probiotic was explored by means of absorbance,particle size and morphology,etc.Moreover,quercetin had the most probiotic effects.Finally,the stability experiment and application test were used to evaluate the protective effect of the hierarchical coacervates for L and explore its potential application.The simulated gastric juice experiment and heat resistance test displayed that the rutin-probiotic co-encapsulation system had the best protective effect.The logarithmic viable bacteria count of the former increased from 2.32 Log cfu/mL to 7.3 Log cfu/mL and the logarithmic viable count of the latter increased from 0 to 3.89 Log Log cfu/mL.Intestinal fluid release experiment demonstrated that the hierarchical coacervate had sustained release effect on L.The relevant data revealed that the storage stability of quercetinprobiotic co-encapsulation system was better.The application experiment of yogurt depicted that the addition of hierarchical coacervates loading with probiotic had little effect on the pH and titratable acidity of yogurt system.(3)In this paper,hierarchical particles and coacervates were used as stabilizers to construct the Pickering emulsion loading probiotic and polyphenol respectively in the interfacial and the oil phase.Co-encapsulation of different polyphenol(Curcumin,Quercetin and Rutin)and L was realized in the form of hierarchical emulsion carrier.The results showed that the particle stabilized emulsion with CS concentration of 0.5 mg/mL and pH 3.0 had more stable network structure,higher lipid embedding rate and higher cell survival.The existence of hierarchical structure in the emulsion system eliminated the negative effect of low pH environment on probiotic.In the co-encapsulated emulsion system,polyphenols loaded by interfacial particles could reduce the emulsion particle diameter,enhance their anti-deformation ability,and improve the encapsulation efficiency for the oil and probiotic.The simulated gastroenteric test displayed that the polyphenol-L-co-encapsulated emulsion could effectively protect L to reach the intestinal tract.Heat stability and storage stability experiments depicted that the co-encapsulated emulsion system could reduce the loss of viable bacteria.