| Developing an effective delivery system to improve the stability and bioavailability of functional ingredients are the urgent issues to be solved in the field of food nutrition and health.Thanks to the adsorption of particle emulsifiers at the oil-water interface,Pickering emulsion can be preferably employed to deliver functional components with the adjustability of interfacial layer,which could be of great value for the stable existence and controlled release delivery of functional ingredients.To meet the application requirements of particles suitable for Pickering emulsion delivery system,this thesis developed oxidized starch/?-lactoglobulin composite nanoparticles with a certain interface wettability through microfluidic heterocoagulation technology,and discussed the formation of composite nanoparticles and the interaction behaviors between oxidized starch and?-lactoglobulin during microfluidic operations.More importantly,we revealed the preliminary mechanism involving the stabilizing effect of the obtained colloidal particles on Pickering emulsion and the controlled-release behavior of functional ingredients,which has important academic value and guiding significance in the construction of food-grade Pickering emulsion delivery system for enhancing the functional activities of nutrition and health food.Based on the intermolecular interactions between starch and protein molecules at the oil-water interface in combination with the structural features of solid particles applying in Pickering emulsion,we systematically studied the effect of sample concentration,pump flow rate of injection port and fluid velocity in the microfluidic channel on the coacervation of oxidized starch and?-lactoglobulin.Furthermore,the effect of p H,the carboxyl content of oxidized starch and the ratio of oxidized starch and?-lactoglobulin on particle size,particle wettability and surface tension were evaluated with the help of the comprehensive analysis(nephelometry,ITC,DLS and contact angle),thus obtaining?-lactoglobulin-oxidized starch composite nanoparticles.The results show that the obtained particles with the average particle size of 380.1 nm have significant interfacial properties through the joint driving force of electrostatic interaction and hydrogen bonding,which were with the characteristics of a contact angle of 86.68~o and interfacial intension value of 4.84 m N/m under this fabrication conditions of p H=4.0,Oxidized starch-?-lactoglobulin ratio of 2:10 and carboxyl content of0.72%.As a solid emulsion stabilizer,the prepared oxidized starch/?-lactoglobulin complex particles were used in the construction of Pickering emulsion delivery system.The effect of addition amounts of colloidal particles,oil/water ratio,salt concentrations on storage stability,dilution stability,rheological property and adsorption characteristics of the developed emulsion.The results show that the prepared emulsions all exhibit significant dilution stability and its storage stability was gradually improved with the increase of particles addition amount.The developed emulsions presented the optimized stability at an oil/water ratio of 1:4,while the excessive addition of salt ions will destroy the overall emulsion stability.Rheological analysis suggests that the pseudoplastic Pickering emulsion all presented shear thinning behaviors under different preparation conditions.The higher the particle addition amount and the closer the oil-water ratio is to 1,the greater the viscosity of the obtained emulsion.The viscosity of the emulsion decreases when the salt ion contents is<20m M.Once beyond this range,the emulsion viscosity increases.CLSM images revealed that the composite particles were adsorbed on the surface of the emulsion droplets to form stable interfacial film,thus obtaining a stable Pickering emulsion delivery system.The comprehensive storage stability of astaxanthin-loaded Pickering emulsion delivery system in the presence of Oxidized starch and?-lactoglobulin composite particles was evaluated under extreme conditions(high temperature,ultraviolet light,and strong oxidants).The findings suggested that the developed delivery system performs significant stability against thermal and UV light treatment,and stability against strong oxidants that needs to be further improved.Based on this,In vitro simulated digestion tests were employed to understand the release characteristics and possible mechanisms of astaxanthin-loaded Pickering emulsions.By simulating oral-stomach-small intestine digestive process,astaxanthin-loaded Pickering emulsions presented a certain stability against salivary enzymes and a slight release behavior due to the decreased interactions between?-lactoglobulin-oxidized starch in simulated gastric juice.Moreover,the gradual disappearance of the interfacial layer of emulsifier molecules improved the release and adsorption of astaxanthin in the lipid phase due to the erosion of particle networks,thereby enhancing the bioavailability and bioaccessibility of functional ingredients.Based on the intermolecular interactions between starch and protein molecules,the present thesis developed the optimal Oxidized starch and?-lactoglobulin composite formulation suitable for Pickering emulsion-based delivery system by controlling the heterocoagulation of?-lactoglobulin and oxidized starch during microfluidic operations,and revealed the mutual relationship between Oxidized starch and?-lactoglobulin heterocoagulation,interfacial properties of Oxidized starch and?-lactoglobulin particle and astaxanthin controlled release characteristics.The obtained Pickering emulsion delivery system in the presence of Oxidized starch and?-lactoglobulin composite particles exhibited good loading capacity and stability,controlled release delivery behaviors.This formulation may provide a theoretical framework and technical support for the development of functional ingredient-loaded Pickering emulsion delivery system and the enhancement of food bioaccessibility. |
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