| In recent years,emulsions have been increasingly used in the food,pharmaceutical,materials and agricultural industries.Oil-in-water(O / W)emulsion systems are the main technical means of encapsulating chemically unstable components and are able to encapsulate non-water-soluble substances to improve their bioavailability,have good stability and can be used to extend the shelf life of commodities.Zein has a special amino acid composition with a large number of hydrophobic amino acids in its molecules,accounting for approximately 50% of the total amino acids,which can produce strong hydrophobicity and can self-assemble into nanoparticles.Currently,food-grade Pickering particles are mainly prepared from raw materials such as whey protein and soybean isolate protein,and Zein is rarely used as an emulsifier/stabilizer in emulsion systems.In this study,Zein,gum acacia,curcumin and gum arabic were used as raw materials to form binary and ternary particles.The lipid oxidation,in vitro digestive properties and bioavailability of β-carotene in emulsions prepared from binary and ternary particles were investigated.The main findings and conclusions are as follows.(1)Weakly charged Zein-GK nanocomposite particles were prepared at p H 4.0.The prepared particles exhibited near-neutral wettability when the Zein/GK mass ratio was 1:1.CLSM images fully confirmed that the ZGKPs could be stably located at the O/W interface and formed a very distinct steric barrier to ensure the stability of the emulsion.In addition,rheological measurements showed that increasing the oil phase volume ratio and the concentration of ZGKPs in the emulsion increased the apparent viscosity and storage modulus,thereby promoting changes in the mechanical properties of the emulsion.By observation of the emulsion droplets,the droplet size decreased with increasing particle concentration or decreasing oil fraction.After one month storage tests,the appropriate ratio will effectively suppress the gravitational separation phenomenon and provide good long-term storage stability.(2)The Zein-curcumin covalent compound(Z—Cur)was prepared by inverse solvent titration at p H 9.0.The maize alcoholic protein-curcumin non-covalent complex(Z--Cur)was prepared by the same method in proportion at p H 7.0.The absorption intensities of the conjugate and the mixture were much higher than those of the native maize alcoholic protein,and the absorbance of the conjugate was significantly higher than that of the physical mixture.The native zeaxolysins formed irregular spheres with a very rough surface,whereas the zeaxolysin-polyphenol complexes formed a relatively smooth surface and the zeaxolysin-curcumin conjugates had a much smoother surface than the native zeaxolysins.The covalent linkage of curcumin to zeaxolysin had very little effect on the surface charge loading,in contrast to the results reported for other species of polyphenols on zeaxolysin.The covalent binding of zeaxolysin to curcumin molecules did not significantly increase the particle size of the conjugates;the conjugates showed a slightly higher antioxidant capacity compared to the mixture.However,all were greatly enhanced compared to Zein.(3)Zein-curcumin-polysaccharide nanoparticles significantly retarded the degradation of β-carotene under UV light and the rate of increase in LH concentration decreased significantly,indicating that the ternary particles stabilized the oxidative properties of the Pickering emulsion significantly better than the binary particles.Simulated gastrointestinal studies showed that the bioavailability of β-carotene was better for ternary particles due to binary particles and that covalent binding was better than noncovalent.In addition,samples containing weakly charged polysaccharide(gum acacia)particles were significantly more effective than particles from highly charged(arabinoxylan)samples.The Z-Cur GK21-stabilised emulsion had the highest bioavailability of all samples. |
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