| Pickering emulsion is an emulsion system formed by solid particles as stabilizer.Due to its high stability and good safety factor,Pickering emulsion has important application potential in food,medicine,cosmetics and other industries.Food-grade Pickering particles have attracted extensive attention from food researchers at home and abroad because of their environmental friendliness,anti-coalescence stability and biocompatibility.At present,the research of food-grade Pickering emulsion mainly focuses on the stabilizers of food-grade biomolecule particles,and there is insufficient research on the stabilization of small-molecule particles and the transport of functional substances in Pickering emulsion.Cyclodextrin,a small molecule cyclic oligosaccharide,has a cavity structure that is hydrophobic inside and hydrophilic outside.It can form composites with varieties functional components and has important potential in stabilizing Pickering emulsion and conveying functional substances.Based on this,in this study,cyclodextrin and cyclodextrin composites were used as the stabilizer of Pickering emulsion to construct Pickering emulsion system,and the microstructure,physical and chemical properties,stability mechanism,oxidation stability,digestive characteristics and functional substance delivery of cyclodextrin and cyclodextrin composites Pickering emulsion were systematically studied.The main results are as follows:（1）Pickering emulsion system was constructed withα-cyclodextrin,β-cyclodextrin,γ-cyclodextrin,cyclodextrinα-cyclodextrin,hydroxypropylβ-cyclodextrin and hydroxypropylγ-cyclodextrin as stabilizers,and the effects of cyclodextrin structure on the microstructure,rheology and stability of Pickering emulsion were compared.Contact angles（25.58±1.92°,35.96±1.94°,21.51±0.48°）and surface tension（55.81±0.04,57.09±0.40,60.18±0.53）ofα-cyclodextrin,β-cyclodextrin andγ-cyclodextrin m M/m)and interfacial tension（6.37±0.08,10.16±0.27,17.45±0.25）were better than those of hydroxypropyl-α-cyclodextrin,hydroxypropyl-β-cyclodextrin and hydroxypropyl-γ-cyclodextrin.α-cyclodextrin,β-cyclodextrin andγ-cyclodextrin can reduce the interfacial tension of oil and water and form a stable interfacial layer structure.The high water solubility and low crystallinity of hydroxypropyl-α-cyclodextrin,hydroxypropyl-β-cyclodextrin and hydroxypropyl-γ-cyclodextrin made it impossible to form a solid interface layer at the oil-water interface,and the emulsion phase separation occurs in a short time.α-cyclodextrin,β-cyclodextrin andγ-cyclodextrin Pickering emulsion had small droplet size,high energy storage modulus,loss modulus and apparent viscosity,good storage stability and centrifugal stability.（2）Cinamaldehyde/cyclodextrin composites were prepared by aqueous solution with cinnamaldehyde as the core material andα-cyclodextrin,β-cyclodextrin andγ-cyclodextrin as the wall material.Cinamaldehyde/cyclodextrin composites was characterized by Fourier infrared spectroscopy（FTIR）,X-ray diffraction（XRD）and thermogravimetric analysis（TGA）.Cinnamaldehyde entered into the cavity structure of cyclodextrin to form amphiphilic complex,among whichβ-cyclodextrin had the strongest inclusion ability for cinnamaldehyde,with the highest inclusion rate of 98.15%.The introduction of cinnamaldehyde reduced the number of crystalline regions of cyclodextrin and weakened the hydrogen bond interaction.Functional Pickering emulsion systems were constructed with cinamaldehyde/cyclodextrin composites as stabilizers.The effects of the formation of cinamaldehyde/cyclodextrin composites on the microstructure,rheological properties and stability of Pickering emulsion were studied.The hydrophobic group of cinnamaldehyde and hydrophilic hydroxyl group of cyclodextrin are arranged in the oil-water interface,and the emulsion droplet form was more compact.The cinnamaldehyde/β-cyclodextrin Pickering emulsion remained stable under long-term storage and high-speed centrifuge conditions.（3）The oxidative stability and in vitro digestion characteristics of Pickering emulsion ofα-cyclodextrin,β-cyclodextrin,γ-cyclodextrin,cinnamaldehyde/α-cyclodextrin,cinnamaldehyde/β-cyclodextrin and cinnamaldehyde/γ-cyclodextrin were studied under simulated oxidative environment and system digestion environment.After the formation of cinnamaldehyde and cyclodextrin composites,the antioxidant effect of cinnamaldehyde effectively slowed down the oxidation rate of Pickering emulsion,cinnamaldehyde/β-cyclodextrin Pickering emulsion oxidation stability was the best,the oxidation induction value can reach 4.63 h.The final release rates of free fatty acids after simulated digestion ofα-cyclodextrin,β-cyclodextrin,γ-cyclodextrin,cinnamaldehyde/α-cyclodextrin,cinnamaldehyde/β-cyclodextrin and cinnamaldehyde/γ-cyclodextrin Pickering emulsion were 77.35±1.49%,64.85±2.59%,81.85±2.99%and 52.32±1.09%,44.32±1.08%,61.47±1.49%,respectively.The oil-water interfacial layer ofα-cyclodextrin,β-cyclodextrin andγ-cyclodextrin is easily hydrolyzed by lipase,and the oil-water interfacial layer of cinnamaldehyde/α-cyclodextrin,cinnamaldehyde/β-cyclodextrin and cinnamaldehyde/γ-cyclodextrin complex was more dense,which was more stable under the action of intestinal digestive enzymes,and the internal oil phase release was slower.（4）The in vivo delivery ofα-tocopherol byβ-cyclodextrin and cinamaldehyde/β-cyclodextrin Pickering emulsion was investigated in Wistar rats to assess the effect of different emulsion delivery systems on the pharmacokinetics and bioavailability ofα-tocopherol.β-cyclodextrin and cinnamaldehyde/β-cyclodextrin Pickering emulsion flocculated and aggregated slightly in the presence of gastric acid,but the structure of the emulsion remained intact.After entering the small intestine,the droplets ofβ-cyclodextrin and cinnamaldehyde/β-cyclodextrin Pickering emulsion decomposed and digested under the action of pancreatic lipase and bile salts.The protection of the interfacial layer ofβ-cyclodextrin and cinnamaldehyde/β-cyclodextrin Pickering emulsion lose,and theα-tocopherol in the internal oil phase gradually released.The maximum dosage curve(AUC（0-t）)and peak concentration(Cmax)of cinamaldehyde/β-cyclodextrin Pickering emulsion were 560.228mg/L*h and 64.32mg/L respectively.The encapsulation and slow release of cinamaldehyde/β-cyclodextrin composites extended the peak time(Tmax)ofα-tocopherol to 5h,and further increased the concentration in blood and digestive tract contents.The bioavailability and slow release ofα-tocopherol can be controlled by the cinnamaldehyde/β-cyclodextrin Pickering delivery system. |
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