Structural Characteristics And Self-assembly Mechanism Of The Binary And Ternary Complexes By Lactoferrin,Curcumin And Oat ?-glucan

In recent years,the market demand for functional foods has gradually increased.Curcumin?Cur?is a polyphenolic substance extracted from the rhizome of turmeric.It is a rare pigment with a diketone structure in the plant kingdom.Cur has received a wide range of biological activity functions such as antibacterial,anti-inflammatory,anti-oxidant and liver protection.Currently,it can be used as a functional factor in food systems.However,as a hydrophobic polyphenol,Cur has a low water solubility and bioavailability,and it is difficult to directly use it in a food system.Therefore,We studied the preparation and structural characterization of binary complexes of lactoferrin?LF?-curcumin?Cur?and lactoferrin?LF?-oat?-glucan?OG?and ternary complexes of three different structures of LF-Cur-OG,which is necessary to develop new Cur carriers.Its application provides scientific basis and theoretical basis in the field of functional food.?1?The rheological properties of OG were studied.Three kinds of OG with purities of 70%,80%and 95%were selected as the research objects.Different concentrations of OG aqueous solution were prepared respectively.Effect of factors such as oscillation frequency,shear rate and temperature on the rheological properties of OG was systematically investigated.The study found that the lower the OG sample concentrations,the closer to the ideal Newtonian fluid state.The higher concentrations?>6%?samples are pseudoplastic fluids,showing typical shear thinning behavior.The Arrhenius equation fit shows that higher concentrations,the higher activation energy and the worse fluidity.The gel critical concentrations of OG with the purities of 70%,80%and 95%are 6%,6%and 5%,respectively.The melting points of the three different purities of OG are 72°C,75.5°C,80°C,indicating that the purity of95%OG has a more stable physical cross-linking network structure.?2?The structural characteristics and binding mechanism of LF and Cur complexes with nature and thermal denaturation were studied.The turbidity,?-potential and particle size of the LF-Cur complexes are closely related to the LF structure and Cur concentrations.The native LF-Cur complexes are nanoparticles?13.32-15.18 nm?at the the Cur concentrations of 14-54?M and the solution has lower turbidity and?-potential.The native LF-Cur complexes are submicrometer particles?0.14-0.33?m?at the the Cur concentrations of 54-108?M and the solution has higher turbidity and lower?-potential.The thermally denatured LF-Cur complexes are nanoparticles?31.77-95.12 nm?at the the Cur concentrations of 14-108?M and the solution has lower turbidity and higher?-potential.Circular dichroism spectroscopy analysis shows that the?-helical content of natural and thermally denatured LF was decreased with an increase of?-sheet and unordered coil contents in the presence of Cur.Infrared spectroscopy analysis indicated that hydrogen bonding is involved in the binding of LF to Cur.Fluorescence spectroscopy results showed that the thermal denaturation LF and Cur had higher binding constants?K_a?and binding sites?n?(3.95×10⁴ M^-1and 0.86,respectively)than natural LF and Cur.Thermal denaturation can increase the embedding rate of LF to Cur.?3?The structural characteristics and molecular interactions of LF and OG with heat treatment and non-heat treatment conditions were studied.At 25 ^oC and 90 ^oC,LF-OG self-assemblies and thermal aggregates can be formed respectively.Fluorescence spectroscopy results show that the presence of OG causes significant changes in the LF seconed structure which is related to the concentrations of OG and heat treatment.Raman spectroscopy and circular dichroism results show that OG can change the secondary structure of LF.Spherical microparticles with a"core-shell"structure can be formed with a particle diameter of about 2.0?m at heat treatment.Thermodynamic analysis shows that LF and OG could spontaneously bind at 25°C,and about the number of 12 LF molecules interacted with one OG molecule.At 80°C,the two are driven by both enthalpy and entropy,and about 99 LF molecules interact with one OG molecule.The binding process of LF to OG involves a variety of non-covalent interactions.?4?The self-assembled LF-OG complexes was used to carry Cur in three addition sequences with spray drying techniques.Three different structures of LF-Cur-OG ternary composites were prepared,and the structures of these complexes were characterized,and their construction mechanism was preliminarily discussed.The results show that the structures the LF-Cur-OG ternary complexes can be adjusted by the Cur concentrations and the order of addition.The ternary complexes solution prepared by spray drying has the lowest turbidity?12.3-26.0 NTU?and the smallest particle size?0.11-0.22?m?by adding sequence 1?OG?LF?Cur?.The antioxidant results showed that the ternary complexes prepared by adding order 3?Cur?OG?LF?had the strongest antioxidant capacity,and the spray drying technique retained the antioxidant activity of the ternary complexes.The rheological results showed that spray drying technique can improve the elastic behavior of the LF-Cur-OG complexes.